One day I got a very terse call from the vice president of the company where I was responsible for fleet maintenance back in the late ‘70s. It seemed that an almost new (1978) Dodge one-ton we had was pointed at the gate with a gooseneck trailer behind it and that truck and trailer needed to arrive at our offshore diving and salvaging dock within the next 30 minutes – 25 miles away. I had no idea why that trip to that dock was so urgent, but someone had misplaced the key to the Dodge.
“Get that truck started and on the road within the next 10 minutes,” he told me with his gravelly voice, “and I don’t care what it takes. Just make it happen.”
I must admit that I was in my element under pressure in those days, so I hung up the phone and grabbed a jumper wire with a couple of ‘gator clips on each end out of my toolbox. I opened the hood on the Dodge and made a connection from the positive battery terminal to the ballast resistor to feed current to the ignition coil.
Making sure the tranny was in neutral, I “pocket screwdrivered” the starter to fire the engine up. Ninety seconds had expired and the steering wheel was still locked, but I knew I could defeat the pewter collar around that silly spring-loaded steering wheel lock peg, and I slid into the seat and muscled the wheel hard to the right, and broke the lock. Mission accomplished in less than three minutes and the truck was headed out the gate.
Some dealership diesel guys I know say they love working on the 6.0L. Why? Well, the main reason is that most of the time it isn’t too hard to figure out what’s wrong with a 6.0L. The weak links in the chain have all been exposed, and there aren’t that many learning experiences (oddball problems that slap a guy around) that happen on a 6 liter any more.
Twenty years ago, the fine tuning available through electronic controls totally changed the face of diesel technology and brought about a cleaner and more efficient family of diesels – Caterpillar’s HEUI system seemed made to order for the job – with oil and fuel rails cast into the iron cylinder heads, special oil-driven injectors and a dedicated high pressure oil pump with a cleverly designed electronic pressure control and feedback system, a new generation of light truck diesels hit the road, and a family of enthusiasts was born within the year. At the dealership as a technician, I personally tested the fuel economy on 7.3L PSD equipped trucks and found those to be capable of about 18 mpg albeit without aftermarket modifications.
The 6.0L emerged in 2003 with a PCM controlled oil piston driven Variable Geometry Turbocharger (VGT), more torque and power than the 7.3L, some new sensors, an EGR valve and cooler and a nasty collection of bugs we’ll have a look at later. Fuel economy on the 6.0L was slightly better than the 7.3L for a conscientious driver. Fuel economy concerns aside, the acceleration and torque on a 6.0L can be pretty astounding for someone who has never driven an electronic diesel.
Came the 6.4L in 2007 – With its Series Sequential Turbocharger System, (consists of one Variable Geometry Turbo (driven by a smart box that can talk back to the PCM) and one fixed turbo, this baby has two EGR coolers and 7 (count ‘em) seven heat exchangers behind the grille. The 6.4L is similar to the 6.0L but with common rail injection, a fuel cooling system, and about 8 mpg in town. Not a good truck for buying groceries and hauling the kids to soccer practice, but it’s happening all over the country.
This article is focused on the functional differences and the weak links on these platforms – can’t cover all the weaknesses (particularly not on the early 6.0L), but we’ll take a swipe at it. Some of these bugs are only a memory – some happen somewhere to somebody every single day.
Field Bugs on the 7.3L
Early problems that surfaced on the PSD 7.3L were deteriorating injector o-rings (we could screw the return line cup off and find small black string-like particles), sticking Injection Pressure Regulators (IPR, mounted on the high pressure pump) that could cause power loss, no starts or MIL lights, crummy little glow plug relays that burned out after only a few thousand miles, failing fuel pumps (that two stage mechanical critter in the engine valley), shorted glow plugs that fried harnesses at and under the valve cover.
Dual Mass flywheel problems can feel exactly like an engine skip that comes and goes at will and can really hammer a troubleshooter who hasn’t experienced that anomaly.
PSD equipped Econoline vans tended to let water to pour past the driver side hood hinge hole onto the Injector Driver Module (that pricey box that takes its orders from the PCM and steps the injector control juice up to 115 volts) and cause anything from funky running concerns and a bevy of odd DTCs to a call for the tow hook.
If the cold weather backpressure control piston malfunctioned (there was no wastegate yet) that flapper choked the beast so that it couldn’t breathe well, the most noticeable symptom was a nastily consistent lack of power.
Additional concerns were shorted fuel heaters that would blow a critical fuse and kill the vehicle, bad or intermittent cam sensors. As the miles wore on, wire connectors would corrode and cause signal and trigger loss. Low pressure oil system concerns would cause hard starts (empty high pump oil reservoir) or a stall and hard start after a couple hundred feet of travel (stuck relief valve in the oil filter head). And let’s don’t forget all the running problems caused by failing to change the engine oil, using the wrong kind of engine oil, using off-road diesel, etc.
“Fuel cackle” concerns (an oddly loud diesel sound under load that was abnormal) were dealt with by replacing the #8 injector with a different part number, and technical service bulletins abounded outlining various troubleshooting procedures, not the least of which was a measurement of camshaft end-play for intermittent P0340 codes accompanied by oddball no-starts that wouldn’t go away.
The fuel filter return head vanished in1996. By the time another year passed, those ingeniously designed Caterpillar mechanical split shot injectors had been installed in quite a few trucks, a maneuver that smoothed and quieted the idle by starting the combustion fire early and then adding a second spray of fuel (first developed for California trucks).
In 1998.5 the second generation 7.3L appeared with an electric fuel pump (it features a 20 second run at key on and a hard to access relay that is behind and below the radio in front of the driver’s right knee), mildly extended crank times (the injectors don’t start clicking until the engine has spun for a few seconds), charge air coolers that required the turbo to be wastegated for boost control (there are a lot of square inches in those big aluminum tubes, so psi had to be limited), and some models had 50 amp intake air heaters to do away with white smoke concerns.
By and large, the second generation 7.3L had fewer bugs – corroded pin concerns are still an issue at the big valve cover connector feeding the glow plugs and injectors, and that corrosion can show up at the IPR and ICP sensor connectors as well.
Rebuilt injectors can malfunction dreadfully and dump lots of engine oil through their innards into the mix, particularly as remanufactured injectors become remans for a second, third and who knows how many more times. Leaking low pressure oil pump pickups tubes on a few of these babies gave us aerated oil issues (surges, power loss, etc) that were difficult to fathom, and the little filters hidden in the fuel tank pickup assembly tended to clog on long trips if the tank was trashy.
Exhaust Backpressure Sensor Issues
The EBP sensor is a small $100 transducer that gets its exhaust pressure feed through a small steel pipe and provides input to the PCM – sometimes the feed pipe will clog with soot and must be cleaned out, and in some cases, the EBP sensor can short internally, killing the engine and the PCMs ability to communicate with the scan tool. If the PCM won’t talk and the truck won’t start, disconnect the EBP just for the heck of it (it won’t cost anything to disconnect it) to see if you hit pay dirt. The sensor isn’t hard to change. The oil piston built into the base of the turbocharger operates a plate that can close to create backpressure and heat the engine up faster when ambients are less than forty degrees. Believe it or not, the sole purpose of that sometimes troublesome setup is to get the heater working sooner.
High Oil Pressure Feedback Check
The ICP sensor or its pin connections on 7.3Ls can fail in such a way to the PCM and fail to report actual oil rail pressure – if the ICP reading less than about 500 psi, the PCM won’t even operate the injectors, and if you disconnect that sensor and try to start the engine, the PCM defaults to a 725 lb reading, effectively bringing the injectors back online if sufficient pressure is there. So if you have a no-start and you can get the powerplant to come alive by disconnecting the IPR, use your Mag light and have a good look at the connector pins. Note also that the battery voltage should be above 8 volts or so while cranking, else the PCM won’t operate the injectors then either.
So let’s put feet to what we just read: A simple field test you can do in a no-start situation that won’t hurt anything is to disconnect the Injector Control Pressure sensor (ICP), an exercise that forces the PCM to substitute a default Injector Control Pressure reading. If it starts while reading default pressure, you actually have decent high control oil pressure but bad feedback. If it won’t you don’t have enough pressure and the reason for the lack of pressure has to be found. The high pressure pump puts out a lot of pressure but not much volume and the pressure loss can be anything from a bad Injection control Pressure Regulator (IPR) to a pressure leak at one of the injectors. In the shop, we blocked first one head and then the other with special tools connected to the pressure lines – that’s a tried and true method of isolating the bank, but we won’t go into that now
Sometimes, removing the valve covers (not an easy job) and observing the little oil exhaust ports on the injectors will offer a clue as to which injector is losing the pressure. If you see one that’s dumping a lot more oil than the rest of them, that injector needs to be replaced, but you’ll need to drain the oil and fuel rails before removing the guilty nozzle, else a lot of liquid will go gurgling into the cylinder when you pull the injector out, and you don’t want that!
6.0L Bugs – Where to Start?
The early 6.0L was so loaded with bugs it would take pages to catalog them all. That in and of itself was quite amazing in light of the incredible measures ITEC had employed to make the 6.0L as dependable as possible. There were more than twenty quality control test areas each engine had to pass during the assembly process. For example, for the first few months of production, literally every engine that came off the line was being started and run for eighteen seconds. Early plans to relax the intensity of the test beds were discarded when the engine gave as many problems as it did. The hydraulic (fuel and oil) and electrical systems were carefully and exhaustively checked for leaks and shorts respectively, but nothing the assembly plant can do can measure up to the crucible of daily field use by a happy camper or dozer-hauling construction guy.
ITEC’s third generation PSD held on to the high pressure oil system but dumped the tried-and-true Caterpillar design for smaller, more precise Siemens injectors, which operate at a little less than half the voltage (slightly less than 50 volts) and with two tiny solenoids operating a spool valve on each injector to control both the opening and the closing of the injector. The high pressure oil rails on the 6.0L are removable, and screwing out the bracket screws neatly unseats the injectors. The glow plugs are accessible by simply removing the wire bus that feeds them instead of having to jerk the rocker arm covers as was necessary on the 7.3L.
The high pressure oil pump is in the rear of the engine mounted in a reservoir and driven by helical gears spinning between the flywheel and the engine block (tidily sealed in a splash oil chamber), and according to ITEC, the flywheel hub can’t be removed without requiring crankshaft replacement. The ICP regulator and sensor began their 6.0L career on the high pressure pump housing, which makes them both rather difficult to access in a pickup truck, but a little more than a year later the ICP sensor was moved to the right hand oil rail near the glow plug relay controller, and techs were very appreciative.
|As an interesting side note, I spoke with a laboratory engineer at the engine plant who told me that the pistons on a hot 6.0L come with .007 inch of the head after everything has expanded to the max, which is pretty scary when you consider the speed with which all those high-dollar parts are moving.|
The split shot injector function on the 6.0L was programmed into the operating strategy rather than mechanically handled the way the Caterpillar nozzles did it, but according to one ITEC engineer I interviewed at the assembly plant, too many of the early Siemens injectors weren’t able to perform rapidly enough to split the fuel shot smoothly, and rough/rolling idle warm, and lack of power cold concerns led the engineers to release a PCM re-flash that did away with the split shot function. The moral of that story is that product variability in the field that can’t be overcome by PCM adaptive learning has to be handled with a reflash (software) or a component (hardware) upgrade. The concerns addressed by removing the split shot were initially addressed by replacing the ICP sensors on problem vehicles with an updated part, but finally the PCM reflash (Ford TSB 03-20-12) was released on October 6 2003.
|FACTOID For old diesel buffs: The pop pressure on 6.0L injectors is 3,100 lbs psi.|
The down side of that split-shot killing upgrade was a fuel economy dump that hammered the mpg down to about 13 on a good day, but undoing the reflash wasn’t an option, thanks a lot!
Between the heads on the 6.0L there is a flat deck that rims the high pressure oil pump and oil cooler reservoir chambers, and since those are pressurized chambers, the gaskets under the oil cooler and high pressure oil pumps can leak oil and sometimes do. Pouring in some dye and pressurizing a warm oil gallery with shop air is the optimum way to find those leaks.
Harness chafing seemed to be the order of the day for many a production cycle. With wire harnesses as thick as a woman’s wrist and lots of dandy little places for the wires to rub through to the copper, Ford
found the need to publish several pages of photos cataloging harness chafe points on various vehicles that could cause a gaggle of issues too numerous to mention here.
Some people are sticklers for every little thing; one 6.0L owner, a friend of mine that I’ll call ‘Joe Bob’ was up in arms down here in Alabama because he found a minute amount of engine oil puddled in his intercooler hoses, but I was able to calm him down a bit by explaining that the PCV system wafts some oil steam into those passages and when it condenses, a small amount of oil is to be expected there.
“Shut up and enjoy the truck, Joe Bob, there’s nothing wrong with it.” I told him.
|For Serious PSD Gearheads and Engineers|
|When EGR rates are being commanded by the PCM and when the engine enters into either one of two particularly specified operating ranges, the PCM program is written to perform an EGR flow check.
At the juncture, EGR flow is estimated based on the difference between the Mass Air Flow (MAF) sensor reading and the total mass air flow calculated by the speed density calculation. The estimated EGR flow is then compared to the expected EGR flow to determine if there is insufficient or excessive flow.
The EGR system on the 6.0L has what looks a lot like a GM EGR valve but it has to be removed with a special tool, and coking problems in the intake and EGR passages run rampant if substandard fuel is pumped through the mill. Ford’s position is that the system can clean itself up if not totally clogged, but it’ll take a few tanks of good clean fuel to make it happen. Let us digress to say that the manufacturer’s advice on biofuels is that they are not to be used in excess of 5% of the total blend or driveability problems may occur. Some biofuel users may disagree.
There’s an important heat exchanger called the EGR cooler on the 6.0L EGR system that cools the exhaust gas as its being recirculated – after all, we’re trying to get rid of NOx, (various compounds from atmospheric nitrogen and oxygen locked together during 2500°F + combustion temps) and since the exhaust is being recirculated to reduce combustion heat, why add hot gas to an already scorching situation?
Incidentally, with the EGR valve open and exhaust gas flowing on a 6.0L, the engine runs so quietly that it doesn’t sound like a diesel, and the PCM may operate the EGR valve even at idle, which is an abnormality for those of us who are more accustomed to gas burner logic.
The first 6.0L EGR system was equipped with a throttle plate to create the pressure differential necessary to make EGR flow. Think about it – if the intake is under boost pressure, how can exhaust gas get in there in sufficient quantity to do any good? The EGR-assisting throttle plate disappeared in late 2004, replaced with an ingenious but not complicated scoop in the EGR supply pipe that naturally forced the exhaust gas into the intake. Incidentally, Duramax uses a throttle plate for the same reason. The 6.OL also uses a Mass Airflow Sensor (MAF) as a part of the EGR control feedback monitor.
The throttle plate that disappeared on the 6.0L came back on the 6.4L, but for a different reason. More about that later.
Pedal Pots and Stuff
Let’s digress again for a moment or two to review a critical element of the trusty old 7.3L. No PSD has ever had a throttle cable, and most PSD enthusiasts know that the accelerator pedal on those units has a potentiometer and a backup micro switch that are collectively structured to be a redundant pedal position check. Not a bad idea, especially if you consider the nasty prospect of a runaway. You don’t have the brakes to stop one of these babies if it thunders into its power curve and out of control!
If the micro switch (called the Idle Validation Switch, or IVS) fails to agree with the reported position of the potentiometer, the 7.3L won’t run above idle. Ever been there? The whole pedal assembly has to be replaced if either the sensor or the switch fails. I’ve seen a few of those (saw one a couple of weeks back), and might I suggest at this point that if you’re an avid 7.3L pilot it would be a good idea to keep a new pedal assembly for your truck in that box of goodies along with your extra glow plug relay and fuel filter, especially if you travel a lot. Get the right one for your model year – they changed every couple of years, and there are about 4 different part numbers. With a 10mm socket you can work the nuts, do the wires and ten minutes later you’re back in the wind.
Now for the 6.0L version: it has three pots on the pedal that are redundant, but to the untrained eye, even on a graph, there’s little rhyme or reason to the voltages – suffice to say that they all have to operate within the parameters expected by the PCM or the engine will only operate at low idle. Medium duty Ford trucks have a 7.3L type setup with one pot and an IVS.
Speed and Position
On the 6.0L, the crank sensor (CKP) reads speed and position as a notched 60-2 tooth trigger wheel goes whirling past it (Duramax uses a 60-3 wheel, go figure), and the crank sensor doesn’t generally give a lot of trouble, but the camshaft sensor (CMP) reads cam position (for injector timing and misfire detection) from a peg pressed into a hole drilled in the camshaft. Both these signals are buffered and sent to the FICM to be used for injector operation, so the mill will only spin but not fire if either sensor is offline.
If that camshaft trigger peg gets loose enough to find its way out of the hole and into the oil pan, the cam signal may be lost, so if you’re chasing the reason for an absent cam sensor signal and the wires are okay, and if you’ve replaced that long skinny cam sensor to no avail, be ready to peer into the cam sensor hole with the necessary equipment (light and mirror, borescope, etc.) while somebody bars the engine over – if you see an empty hole instead of a trigger peg, it’s time for the hook and some major surgery.
Incidentally, the misfire monitor doesn’t operate above 750 rpm on a 6.0L because it wouldn’t be accurate anyway, and on a 6.0L (according to the 6.0L OBDII service manual), misfire is defined as a loss of compression, but it’ll take a 3/16 hole or bigger in a piston or valve to trigger a misfire code.
Remember, the old 7.3L didn’t have a crank sensor or an Engine Coolant Temp sensor – it only measured the temperature of the engine oil via an EOT sensor.
Pressures – Fuel and Oil
Fuel Pressure: If the fuel pump (located on the frame in the Horizontal Fuel Conditioning Module) shuts down, the injectors will generally suck fuel to their nozzles all by their own action, but there isn’t much of anything that will destroy a set of injectors faster than a low or no fuel pressure concern, so pay close attention to fuel pressure, which should be from 45 to 55 psi, and there’s an Allen plug on the secondary filter (out by the engine oil filter up top) where fuel pressure is supposed to be checked with an adapter that feeds the gauge.
Important note: The electric pump on a 6.0L is very hard to hear, so don’t depend on your ears to determine whether it’s running or not unless you have a mechanic’s stethoscope, and remember that the HFCM has a filter in it as well, so you should keep an eye on it. Depending on the model year, there’s a plug or a lever on the HFCM to drain the water and/or fuel out of the unit when you’re planning to service the primary filter.
Oil Pressure: The high pressure oil system that drives the injectors on a 6.0L can’t work without lube oil pressure, which comes from the familiar old gerotor style oil pump driven by two flats on the nose of the crankshaft. The oil pump and its relief valve are both built into the timing cover housing and the relief valve is below and behind the balancer and is fairly accessible. If you screw the relief valve plug out and the relief valve is stuck in its bore, it’ll shove the spring and plug out of the hole. If it’s not stuck, you can take the plug out without a shove and fish the spring and valve plunger out for inspection. The valve should slide smoothly in and out of the bore and not have a lot of scoring or marks on it.
Think you may have low oil pressure system concerns? Here’s the deal: Screw the oil filter cap off, remove the oil filter, and press the button in the bottom of the oil filter chamber behind the stand pipe to drain that chamber– you should do that anyway to release the dirty oil, and the first time you find it, you’ll remember where it is the next time. Next, spin the engine over while looking down into the chamber – it should rapidly fill with engine oil. If it doesn’t the engine is either out of oil or you have no lube oil system pressure. Check the relief valve and if it has shavings fouling it you may as well remove the timing cover and replace the oil pump, but that’s not a job for a home boy.
High Pressure Oil: Among the most recent and numerous problems on newer 6.0Ls, there is an oil line with a quick disconnect that likes to pop off of the branch tube and dump the high oil pressure, which renders the engine inoperative. The branch tube, a bracket, and a new High Pressure Pump outlet fitting is required, and there’s a TSB. Once again, don’t try to fix this at home – it takes a lot of, training and gumption to straighten this problem out – more time, energy, and toolery than most of us have.
Revisiting a Major Problem
I wrote some time ago about a situation I saw when the 6.0L was brand new and the 2003s were still on the showroom floor. Here’s a short recap.
Marty, a technician friend of mine was checking an early 6.0L with power loss concerns that grew worse until the unit finally stalled and refused to restart. Disclaimer: Marty is an extremely competent technician, but he’s not a Power Stroke specialist. (The PSD guy was out sick with a virus) Marty’s initial inspection revealed a bad turbocharger.
The turbine shaft was wallowing around on wiped out bearings, and that in and of itself seemed strange with only 2500 miles; the truck wasn’t even due for an oil change yet! After replacing the turbocharger and then destroying the brand new one in a single 7 mile test drive, Marty pulled the dipstick and found that the crankcase was ridiculously overfull with something that felt more like diesel fuel than engine oil.
Draining the crankcase, Marty found no less than seven gallons of liquid, and it was as thin as sewing machine oil. The engine bearings probably didn’t suffer enough to matter (who knows for sure?), but turbocharger bearings carrying a turbine/impeller shaft spinning at speeds approaching 100,000 rpm simply won’t survive under lousy lube conditions like this.
Using the block heater to warm the engine (standard procedure for any PSD leak detection process, no matter what fluid is leaking), Marty put dye in the fuel, pressurized the fuel system, and found diesel leaking, not from the o-ring at the base of the injector as he and I had originally supposed, but from the injector body on most of the injectors, effectively dumping fuel into the crankcase.
This problem surfaced on more than a few trucks before Ford and Siemens got the problem straightened out, and most of you guys and gals probably know somebody who experienced this failure or one like it.
Some 6.0Ls come in skipping and smoking with low compression on certain cylinders, and with the head removed, scars on the cylinder walls have always led the factory folks to call for the engine to be removed, reassembled to be shipped back to the plant, and replaced with a new unit.
One of these episodes I saw involved an engine with some Banks performance modifications, but none of us could say for sure that the Banks hardware/software changes actually caused the trouble, and since Ford wouldn’t pay for exploratory surgery, it was difficult to tell what was going on between the piston and cylinder that caused the scars. Signs of overfueling due to aftermarket mods are fairly easy to spot with the head removed – the injector spray pattern on piston crowns is far more pronounced on an over-fueled 6.0L and more than a few digital photos of those have been fired off to Ford and ITEC to the chagrin of customers whose warranties were in jeopardy.
One Day During a PDI…
Eddie called for my judgment while he was fighting a new 6.0L truck with almost no miles that would run for about thirty seconds and die – as soon as it died, the Fuel Injector Control Module would stop talking to the PCM. Switching the key off and rebooting, Eddie could duplicate the concern repeatedly.
In a situation like that when there are other new trucks on waiting to be pre-delivered, an A-B-A swap is viable, but I cautioned Eddie against snatching the FICM from another new truck and plugging it in to the problem vehicle. If the problem truck had some kind of short circuit or voltage surge condition that destroyed the FICM, the last thing he needed to do was plug a pristine new unit into a truck that might be waiting to eat another expensive electronic box. So what’s the answer? Put the suspect bad FICM on a good truck – the bad FICM is a LOT less likely to damage the good truck, but a bad truck usually will destroy a good FICM.
End of that story – the good truck performed like the bad truck with the bad truck’s FICM installed. FICM replaced. Case closed.
EBP – the VGT’s Feedback
The Variable Geometry Turbo relies pretty heavily on the Exhaust Backpressure Transducer, and if you have a surge that you can hear or even feel, try disconnecting the EBP and doing a short test drive. You’ll probably hear a funky rattling noise in the intake during this exercise, but if the surge goes away, chances are you need a VGT actuator, that little PCM-controlled oil piston that uses engine lube oil pressure to drive a rack and operate the VGT vanes. Let’s talk for a moment about that VGT.
The Duramax uses basically the same turbocharger as the 6.0L, but is equipped with a vane position sensor that reads the position of an eccentric and feeds that info to that vehicle’s ECM, and I’ve been told that the Duramax turbo uses some stainless steel parts, but I couldn’t verify that piece of data.
The 6.0L has a blind steel plug in that vane position sensor hole and uses the EBP transducer and Manifold Absolute Pressure (MAP) reading for feedback. When the turbocharger vanes are closed, they slow the exhaust and spray it faster onto the vanes, speeding up the turbocharger and forcing it to act like a smaller unit, a maneuver that effectively eliminates turbo lag and gives the 6.0L that crisp acceleration. This added backpressure also helps with cab heat cold weather much the same way like the turbo backpressure flapper did on the original 7.3L. As engine demand increases, the vanes open wider, slowing the turbocharger to protect it while still enabling it to work like a large turbocharger.
Is your cooling system de-gas bottle blowing coolant out when you pull a trailer even though it’s not over filled? Is your coolant contaminated with engine oil? You may have blown head gaskets or a clogged engine oil cooler, but don’t jump too soon – it takes a real cowboy with the right tools to ferret out the cause.
The engine coolant flow on a 6.0L is through the EGR cooler, then it goes to the engine oil cooler (which is beneath the oil filter). If the engine oil cooler clogs enough to restrict coolant flow then it can eventually burst the EGR cooler. And here’s a nasty: That repair won’t be a warranty fix if you’ve done performance mods!
Turbocharger seals fail sometimes and blow oil through the intake system – the symptom is a tendency of the charge air cooler hoses to blow off under boost conditions, because the oil mist makes the rubber joints slippery and prone to disconnect in spite of the big clamps. Jimmy (a graduate of my automotive program) was replacing a turbo today for that very reason.
Not Many Bugs on the 6.4L!
The 6.4L, since it is a common rail system (the troublesome high pressure oil system has been eliminated), has a fuel temperature sensor, a fuel cooler with a dedicated supply of coolant and a PCM controlled pump, and a fuel pressure sensor in the right side common rail. The head bolts are 16mm as opposed to the old 14mm bolts used on the 6.0L.
The automatic transmission flex plate on 6.4 has two extra bolts and while the helical cut gears between the flywheel and the block look just like the ones used on 6.0L, they are different, and they drive the high pressure fuel pump, which is mounted in the same place where the high pressure oil pump was on the 6.0L.
Visteon makes the radiators on the 6.4L and there have been some leakage concerns. Not counting the fire-from-the-tailpipe issue we all saw on YouTube there are a couple of reflashes for a certain group of trouble codes, a couple of wiring problems and a gurgling noise in the heater core.
The fuel pressure from the HFCM is fairly gentle as it is fed to the engine but it is boosted to killer pressures by the radial piston high pressure pump, which has a solenoid vaguely similar to the ICP regulator on the 6.0L, and it controls the pressure to the injectors. The injectors contain a stack of piezoelectric disks that shrink .001 inch when energized, and since the same fuel pressure is below the long pintle and above it as well, shrinking the piezo disks bleeds the pressure from above the pintle and allows it to pop. This kind of fuel control is crazily accurate.
The passages (front of each head) where fuel was fed to the injectors on the 6.0L are actually the return path on the 6.4L, and there are of necessity no check valves in the banjo bolts on this engine, so don’t try to retrofit.
The turbochargers operate in series – one turbo is a low pressure unit and the other is a high pressure turbo, but the VGT on this one is controlled by a smart actuator that is actually cooled by the same pump and cooling system as the fuel itself. In a word, any turbo angle requested by the PCM is considered by the smart turbo actuator, and if the actuator is too hot, it won’t cooperate until the PCM turns the coolant pump on so the actuator can cool off.
There are two EGR coolers (also in series), a sensor measuring exhaust temperature going into the coolers and another temp sensor on the outbound side of the coolers. To combat the coking problem, the exhaust gas goes through a miniature catalyst of sorts on its way to the EGR system, and so far that little rascal is doing pretty well.
The particulate filter has to regenerate every so often (the PCM does it actively when passive regeneration doesn’t get the job done) and it uses some extra fuel in the process – that may be why the 6.4L tends to use more fuel than the 6.0L. Particulate filter regeneration will happen between 100 and 600 miles and won’t last as long if road speed above 38 mph is maintained. Sensitive customers can feel regeneration taking place, and the PCM’s operating strategies are a bit different during regeneration, which, by the way, is what the throttle plate on the 6.4 is used for.
A Green Conclusion
The 6.4L actually cleans the air as it runs, but it does produce carbon dioxide, the very gas that feeds trees and grass, so it’s kind of hard to understand why the folks that don’t like CO2 are called “Greens.” If they had their way, the carbon dioxide would be gone and the trees and grass would barely be able to survive.
A brief look at the B series Cummins engine that gives Dodge its diesel power.
When pickup trucks started going diesel ‘way back in the early eighties, Ford opted for the International Harvester (Navistar) 6.9 in its heavy duty pickups, while Chevy nestled a 6.2 under the hoods of their heavier duty units. Dodge remained dieselless in their pickup line until the ripe old year of 1989, when the 5.9 liter ISB Cummins became available on pickups heavier than the ½ ton platform.
The B-series Cummins engine has since found a home in a wide range of platforms from the D-250 all the way up to motor homes and Ford medium duty trucks.
Cummins 24 valve rocker cover
A Quick Scan of the Gut Numbers
The turbocharged Cummins ISB series engine is slightly undersquare, with a 4.02 inch bore and a 4.72 inch stroke for 5.9 Liters (359 cubic inches) of displaced air with every two crank revolutions. The compression ratio is moderate for a diesel; 16.5:1 (as opposed to 17.5:1 for the 12-valve engine) and squeezes the full volume of the combustion chambers with High Swirl Bowl aluminum pistons, bringing the air in the cylinders to the superheat required to light off fuel spray from injectors that “pop” at a brawny 4,500 pounds per square inch of pressure. The firing order is the extremely familiar 1-5-3-6-2-4 we’ve all been accustomed to for decades on straight-six engines (not that you’d cross the injector lines anyway!). The crankshaft is Induction Hardened Forged Steel, while the camshaft is “Chilled Ductile Iron” according to Chrysler’s shop manual.
Horsepower on the automatic trans equipped diesel Dodge peaks out at 215 (from 1600 rpm to 2700) with 420 foot pounds of torque, while the manual trans equipped counterpart is tuned for an additional 20 horses and another 40 foot pounds. of torque. Average engine-life-to-overhaul figures are an astounding 400,000 miles!
Cummins“High Swirl Bowl” piston
(all photos Richard McCuistian)
Fuel Delivery Overview
Fuel systems differ from one application to another in the B-series line; newer Cummins medium duty truck engines appropriate solenoid regulated top-stop injectors with a 17,000 psi gear type fuel pump, the inevitable Cummins Engine Control Module (ECM, mounted on the driver side of the engine in true Cummins style), and a common supply rail. As for the B-series Dodge pickup engine, the fuel is handled by a Bosch VP44 solenoid-controlled-radial-piston-distributor type “Smart Fuel Injection Pump” that supplies the gutsy 4,500 lbs needed to “pop” the vertically centered injectors that spray directly into the combustion chamber. There are no ignition prechambers on the 24 valve Cummins. The Holset turbocharger is matched to the engine and waste-gated for improved performance at all speeds.
The “Smart Fuel Injection Pump” itself is gear-driven (on a tapered shaft with a special keyway; more about that later) at half crankshaft speed by way of the camshaft and contains an integral top-mounted Fuel Injection Pump Control Module (FPCM) that is non-serviceable without replacing the whole pump. The FPCM is energized by the Engine Control Module via the Fuel Injection Pump relay in the Power Distribution Center (PDC). Fuel is supplied to the VP44 pump through the filter/water separator by an vane-type electric transfer pump which is mounted near the ECM. The Transfer Pump is driven at 100 percent duty cycle with the engine running and should produce at least 10 psi. During engine cranking, the pump duty cycle is a mere 25 percent, producing only 7 psi, to limit injector pump inlet pressure until the engine fires up.
Diesel guys will be familiar with the concept that most of the fuel (about 70 percent) passing through the hard-working injector pump is used to keep the pump cool and returns to the fuel tank. And like most other diesels, if you run one of these babies out of fuel the air will have to be bled from at least two injectors before the engine will receive enough fuel spray to light off. Personally I like to bleed ‘em all. The electric transfer pump is kind-hearted enough to be self-priming.
Keeping Things Timed;
The All-important Keyway.
1. Order No.
2. Bosch Part No.
3. Factory Code
4. Cummins Part No.
5. Manufacture Date
6. Pump Serial Number
7. Last three digits of key
Engine timing and injector pump timing are matched by an offset keyway that is specifically numbered and calibrated to match its own pump. If you bobble the key and it falls down the drain or something, simply check the pump data plate (see illustration) to see which key you’ll need to order. The three digit number stamped on the pump represents the last three digits of the part number of the key for that pump, and the same three digit number will be stamped on the key itself.
Always use a key with the same number stamped on the pump and always aim the arrow on top of the keyway toward the rear of the pump. If the offset key isn’t installed with the arrow pointing toward the pump, or if the gear has slipped on the pump shaft, an “engine sync error” or “static timing error” code will be stored. If such a scenario appears to be the case, simply pop the plastic gear access cover for a quick inspection. If the gear has to be removed for a double check of the key, a T-type puller and a couple of M8 X 1.24 screws will do the job nicely. Don’t move the gear too much or you might break the gear cover. Also, make sure to rotate the engine (Snap-On barring tool No. SP371 is really nice for this) so that the pump key is at the 12 o’clock position before you pull the gear or it can tumble down into the gear housing for a day-ruining foul-up!
Injector Pump closeup Illustration of numbered key (Courtesy Chrysler Corp)
(with FPCM module mounted up top)
photo: Richard McCuistian
Note: The Injector Pump keyway is also used for reference when performing valve adjustments on the Dodge Diesel. The intake valves optimum lash spec is 0.010 inch (0.006 -0.015). and the exhaust valves optimum adjustment is 0.020 inch (0.015 – 0.030).
Keyway positions (Courtesy Chrysler)
Three Brains are Better Than One…
The 9-pin Fuel Pump Control Module (FPCM) built into the VP44 pump partners with a separately serviceable 50-pin Engine Control Module (ECM) in controlling fuel delivery, while a third module more familiarly named the “Powertrain Control Module” (PCM) is used to regulate and control the Climate Control, charging, and speed control systems, as well as certain automatic transmission components and it also interfaces with the ECM regarding some of the instrument panel indicators. Engine idle speed and injector pump timing are obviously handled electronically. The PCM is mounted in the same place it can be found on gas burners, over on the passenger side of the engine compartment bulkhead, while the ECM is mounted on the driver side of the engine block the way most Cummins Engine Controllers are. One point that might be of interest is that the Cummins ECM for the Dodge Truck Application has only one connector instead of the two connectors found on medium duty truck controllers.
|1||K240 20 LG/PK||Fuel Injector Pump Data Link (-)|
|2||K242 20 WT||Fuel Injector Pump Data Link (+)|
|3||Not Used||Not Used|
|4||K44 18 VT/OR||Camshaft Position Sensor Signal|
|5||K45 18 LB/RD||Knock Sensor Return|
|6||Z12 14 BK/TN||GND|
|7||A40 14 RD/LG||Fuel Pump Relay Output|
|8||K48 18 DG||Fault Signal|
|9||Not Used||Not Used|
Fuel Pump Module Connector Layout according to Chrysler Shop manual. Below is the Chrysler wiring map
for the FPCM and the Engine Controller. (both illustrations courtesy Chrysler Corporation)
The ECM and PCM communicate with each other and the scan tool through Chrysler’s CCD bus circuits (“Chrysler Collision Detection,” which has everything to do with mixing and matching serial data transfer between modules and nothing whatsoever to do with actual collisions), receiving parallel signals and acting accordingly.
Engine Control Module Connector
Accelerator pedal position information is sent to the ECM in the usual way, i.e., as an analog voltage signal proportionate to throttle angle, with the standard 5-volt reference voltage filtered through a linear potentiometer, then the ECM loops it back over to the PCM along with Crank Position info gleaned from the CKP sensor. The Cummins-equipped medium-duty Ford truck Accelerator Pedal Position Sensor (APPS) is mounted on the pedal assembly along with an Idle Validation Switch (IVS) as a backup. The engine won’t rev above an idle if the switch and sensor don’t agree, but on the Dodge, the Accelerator Pedal Position sensor and IVS are actually mounted on a bracket at the injector pump. Earlier units had linkage and bellcranks between the cable-driven sensor shaft and the pump, but the linkage and bellcranks evaporated from the Dodge pickup line late in the ’97 model year, leaving only the APPS attached to the throttle cable, and giving the FPCS control of fuel delivery via the electronic manipulation provided by the ECM.
The APPS is serviced along with the bracket, and while we all like to tinker, the Mopar folks warn us not to go there, since the APPS is calibrated and permanently mounted to its bracket. You can’t get a replacement sensor without buying the lever and bracket assembly anyway.
APPS & Bracket APPS Sensor and bracket
(Illustrations courtesy of Chrysler Corporation)
The Rest of The Crew
Other ECM inputs are Ignition switch input, CKP (Crank Position), WIF (Water in Fuel) sensor, Air Temp Sensor, Oil and Manifold Pressure Sensors, and CMP (Cam Position Sensor). Pins 41 and 40 are CCD Bus pins, where the ECM receives serial data from the PCM. The FPCM talks to the ECM on a separate pair of shielded wires. Other ECM outputs besides the FPCM include the Intake Air Heater relays (two of them, one for each intake grid heater) the Diesel Wait to Start Lamp, the Fuel Transfer pump, and the Injector Pump Relay.
Data for the Driver
Interestingly, Cummins markets a hot little item called “Road Relay 4,” which allows the driver to monitor the vital (and not so vital) signs the Engine Control Module broadcasts over the CCD bus. It was once available only to 18 wheeler drivers, but Cummins has plans to market this handy little electronic device to Dodge Ram owners in the near future. A nice little alternative to the Road Relay 4 is Quick Check II, another interface available through Cummins designed to allow the Cummins Engine Controller to communicate with your PalmTM device.
Cummins Success Dealing With Nox Standards
Diesels pretty much managed to dodge the emissions bullet for a lot of years longer than gas burners. But in 1998, under a settlement of a government suit, seven diesel engine manufacturers agreed to lower Nox emissions on engines in tractors and 18-wheelers by October 2002. Cummins, Navistar International Corp.’s International Truck and Engine Division and Volvo Truck, as well as the Detroit Diesel folks are all meeting the October deadline, but Caterpillar seems to be having trouble with it.
The new government regulation calls for truck engines to certified by the Environmental Protection Agency (EPA) to the 2.5-gram NOx + NMHC standard. Cummins actually met this standard and earned EPA approval on the ISX series engine, shipping its first certified engine early in April 2002.
The primary differences in engineering that enabled Cummins to meet the October deadline seem to center around Holset Variable Geometry Turbocharging (VGT) and a cooled EGR system. The VGT will eliminate wastegating, since the turbocharger uses a single sliding nozzle to regulate turbo boost. It’s not a new idea; Over 40,000 trucks in Europe are already using the new design with tremendous success.
I contacted Cummins with an inquiry as to whether or not the ISB engine would be re-engineered to these standards, and the reply I got was that as of May 21, 2002, the ISB engine has been submitted to the EPA for certification under the new Nox standards. The EPA is expected to render their certification of the ISB early in the summer of 2002, and the ISM engine is expected to be certified by the October deadline. One wrinkle on the ISB is that only engines rated at 245 horsepower and above will receive the VGT. Lower rated turbocharged engines will probably keep their wastegates for a while longer.
Along with the VGT and cooled EGR, on the higher powered units, all the new ISB engines will lose their Bosch injector pumps in favor of a “High Pressure Common Rail (HPCR) Fuel System” for reduced noise, as much as a 2% increase in fuel economy, and improved emissions. The gear train will be moved to the rear of the engine, a change which may cause diesel wrench guys to groan, but intended by Cummins to provide increased accessory drive capability and as much as 80% quieter on engines built with both HPCR and the rear gear train. If these claims prove out, it’ll seem strange to hear a diesel that sounds like a gas burner!
CI-4 oils are recommended on the new engines, crafted to meet EGR requirements.
Changes Keep Coming
Diesels are getting quieter, smarter, more powerful and more efficient every year. Who knows what the next decade will bring? Diesel electric trucks maybe?
In a myriad of ways, cars communicate their problems to their drivers. One way is by burning too much gas or bucking and jerking. They can fail to start or start hard. They can overheat or have less than normal power. They can make odd noises. They can turn on warning indicators of various colors and shapes to warn us of issues we might not notice otherwise. They can create weird sensations, either through the steering wheel, the seats, or whatever. And when we take our vehicle in for service, we have to use our human ability to communicate to the service advisor who’s writing the ticket. He or she needs to know what our cars have communicated to us.
That sometimes weary, stressed, and overworked individual (remember, he listens to peoples’ problems all day and gets shouted down a lot when things go sour) has to use very few words in a synopsis of the concern the customer describes, and like the rest of us, sometimes the service writer either doesn’t listen well enough or isn’t told everything the technician needs to know about the concern. Some customers either can’t or don’t want to describe their concern in detail because, well, communication takes energy and effort. One girl who drove a company vehicle when I was doing fleet maintenance 30 years ago would call me when her car gave some kind of trouble and simply say, “Richard…. MY CAR!!!”
This kind of driver just wants to throw their keys at the service advisor on the way to the mall and have their car fixed while they do very little to explain what’s wrong. Unless their concern is painfully obvious, that non-communicative way of doing things just doesn’t work.
“And That’s Gonna Fix it, Right?”
Well, after the work order is written, it becomes a part of the shop’s paper trail and a dispatcher hands it to a technician who will read the description of the customer’s concern and launch his or her diagnostic investigation, find out what’s wrong, get authorization, and make the repair. If things go the way they should, the customer will be satisfied. When he or she isn’t satisfied, well, in a fair percentage of those cases, a breakdown in verbal communication is the problem.
This vehicle just a machine, right? So, in the eyes of the service writer (many of whom haven’t personally done service work), a technician should be able to make a diagnosis in just a few minutes, then promise that that the $320 worth of parts and labor quoted will fix the customer’s vehicle and that nothing else will be needed. If the service writer can extract that kind of promise from the technician, he or she feels really good in making that same promise to the customer and comes off looking like a hero – unless the promise happens not to be kept. No tech with any real experience will make that promise; after all, there is a reason that the words, “Verify Repair” are at the end of every published repair routine where troubleshooting is a part of the equation.
When things work the way they should, the customer has described his or her concern to the best of his/her ability, and the service advisor knows which questions to ask for clarification. Then the service writer/advisor has either typed or written information on the work order that communicates to the technician what the customer wants repaired – with a note to see the service advisor for clarity if there isn’t room on the repair order line to tell the whole story. The service writer/advisor has received communication from the customer, properly creating the work order, and then the technician is supposed to use his/her ability to read and comprehend and has applied knowledge and experience to determine as nearly as possible what has to be done. Then the technician has to test drive the car to make sure the problem is completely fixed.
Even after the authorization has been given, there’s that annoying part of any repair that tends to sour the service advisor’s stomach. When the “Verify the Repair” stage of the job comes to pass, there are times when more work is needed, even when a good technician makes the most accurate diagnosis possible.
Case in point: Following factory training procedures, I once confirmed that the ignition module was faulty on a high mileage Renault Alliance by pressing on the potting material on the back of the module near its wire connector – the engine stalled. The Renault instructor had taught us this as a reliable test for a vehicle with a stalls-while-driving concern.
I communicated this information to the service advisor – he didn’t communicate it to the customer, he only told the man that the module needed replacing. That was enough to obtain authorization for the repair, and I replaced the module, then test drove the car. It didn’t stall on that test drive. A week later the car stalled again and the guy came back.
That time I found a bad crank sensor, but it was far more difficult to get the crank sensor to fail – I had to drive a LONG time with my equipment connected before the sensor stopped working. The customer was totally convinced that he didn’t need the first part, and no amount of communication at this point would un-convince him. Ideally, I would have been able to demonstrate the test procedure I used the first time I checked the car. That would have been perfect communication because he would have seen the problem for himself. As it was, things went kind of sour.
Granted, there are times when the technician simply misdiagnoses the problem, and those are the times that seem to stand out, but misdiagnosis, while it is more prevalent in some shops than others, isn’t the case every time – and the situation is compounded when customers and service writers think they know more than they actually do. In those cases, it doesn’t matter what the truth is, it just matters that they’re ticked off.
“Why Wasn’t I Told…?”
Then there are the land mines that come from communication that is deliberately withheld. For example, I know of a man who bought his vehicle “AS IS” from a used car lot and then found out after his first oil change that the engine was loaded with thick, gooey ‘motor honey’ to keep it from knocking. A simple oil change uncovered a problem that necessitated a massive repair.
Incidentally, one piece of communication that should make any buyer shy away from purchasing a used vehicle from an individual is when the seller says, “I’m not a mechanic…” That typically means the seller knows the vehicle has a hidden problem but wants plausible deniability when things go south, which they usually do.
“It Wasn’t Like That Before..”
There are also those times when one repair leads to another repair that was unrelated, and the mechanic has to communicate to the customer why the work he or she did couldn’t have caused the second problem.
Case in point. My dad put brakes on my sister’s car. As soon as she backed the car out of his shop, her radio wouldn’t work. She replaced the fuse and it blew as soon as she plugged it in. She was convinced that my dad had destroyed her radio while he was replacing the brake pads until I found the problem – a shorted capacitor inside the radio was blowing the fuses. Replacing the brakes had nothing to do with the radio even though the radio was working just fine right before the brakes were replaced. The best way I could communicate that to my sister was to fix her silly radio for free.
Good Communication is Our Job too
When the work is done, particularly if it’s a warranty claim, the technician has to be able to clearly communicate why he or she did the work that was done so that the warranty auditors won’t be able to use the technician’s description of the work for a reason to charge the repair back to the service department. And the work order has to be written truthfully, accurately, and in such a way so it is easy to understand.
One of the most important aspects of communication is to always tell the truth. When a question has arisen about something I did or didn’t do in a shop situation, the management always took me at my word because of my track record of telling the truth. Always remember that. The truth needs to be your friend and ally rather than your enemy. I always say that if everybody always did what they were supposed to and didn’t do what they weren’t supposed to there would be no temptation to lie. That being said, a loud and angry supervisor may find himself left out of the loop sometimes simply because the technician doesn’t want to be shouted down.
I was pulling the rear seat out of a nearly new Lincoln one time and I guess I was kind of clumsy that day, because I managed to scratch the paint behind the passenger side rear door – I immediately fetched the service manager and had him bring the customer to the service area. That silver-haired old banker just smiled and said, “Don’t worry about it – If I decide I can’t live with it, I’ll bring it back and have you guys fix it.” Honesty is the best policy, you see, and it’s a lot easier when your service manager isn’t a jerk. But even when he IS a jerk, honesty is still the best policy.
Case in point: Once back in 1995 I had to do some work on a factory installed cell phone in a Crown Victoria, and about a week later, the service manager called me into his office, claiming I had made a personal call on the customer’s phone. I told him the only call I had made on that man’s phone was to Ford – a necessary call as a part of the repair. He said the phone had been used to call a number right there in town, and I asked him to show me the bill.
“See the timestamp on that call?” The service manager looked where I was pointing at the call he had highlighted.
“That’s eight thirty p.m. …” he mused.
“Where was I at eight thirty?” I asked.
“That call was made by the salesman when he was delivering the car back to the customer!” He almost shouted.
“No duh,” I replied, and left his office, not waiting for the apology I knew wasn’t coming.
Then there’s LATE communication that comes from NO initial communication. One day I couldn’t find my favorite 3/8 ratchet. Two weeks later I still couldn’t find it. Finally I bought a new one ($54) off the tool truck and etched my name on the handle. Later that afternoon, my service writer came from his desk bringing my missing ratchet – said he had borrowed it several days earlier to do a simple recall in the write-up area and had covered it with some papers, then forgot he had it.
Words Fitly Spoken
Communication with customers is extremely important. A technician needs to be able to concisely explain WHY a repair is needed. After the customer is done talking to you, that customer should have confidence in what you know and what you do.
If the customer has no confidence in you, (and that confidence always has to be earned over time) then your employer will have less confidence in you as well. Get credentials. Display them appropriately. Communicate professionally.
And just because you think you know more than other people about some things, well, that doesn’t give you a license to be an arrogant jerk or a rip-off artist. Ever met a mechanic who was an arrogant jerk? He’s insecure and immature. My personal axiom is that it is NOT possible to be both rude and mature at the same time.
At the shop where I worked the longest, the general manager discovered that I could generally calm a customer down even when nobody else could.
Sometimes saying the right words at the right time will do the trick. In those cases, less is more. Example: Customer brings his truck to our shop because the engine hunts and surges when he’s taking off… This one has a stick shift, not an automatic. The technician who worked on it found the problem and corrected it, but the porter who brought the vehicle around wasn’t too good at driving a stick and so it looked to the customer like the truck wasn’t fixed when in reality it was.
The service writers tried to explain the situation but he only shouted them down. He had paid his bill and his truck was “jus’ like it wuz,” so to speak. So I heard my name over the loudspeakers calling me to the writeup area even though I wasn’t the one who did the work.
“Can you talk to this guy? He’s pretty furious and we can’t get him to calm down.”
“Sure,” I said, moving to where the customer was standing with folded arms and an icy glare.
“Let’s take a test drive,” I told him. We settled into the seats of his truck with me behind the wheel and I eased out of the parking lot onto the bypass and then down into the Wiregrass Commons Mall access circle. He ranted while I drove. The truck always accelerated smoothly, every time I took off. I let him rant and rave until he had pretty much spent his emotional energy before I interjected a comment.
“Ya know, I sent a VCR to North American Phillips in Atlanta to have it repaired awhile back, and when I got it back it was still giving the same problem…” He banged a fist on his knee..
“YEAH! That’s what I’m talkin’ about! Ain’t it a pain?” He raved on for another thirty seconds and then calmed down, convinced that I had walked in his shoes at least once. He noticed as I accelerated from a standing stop two or three more times.
“I guess it’s doing better than it was. I guess I’ll just drive it for awhile and see how it does.”
I smiled and nodded, turning off the access road on my way back to the dealership. He drove away satisfied.
For any workplace to operate efficiently, the various players have to communicate accurately. When communication breaks down, the job breaks down. That’s why they stopped building the Tower of Babel, but that’s another story. R.W.M.
Security Button – Power Door Locks Then and Now
According to at least one internet source, the first power door locks appeared in 1914 on the now-obscure and mostly forgotten Scripps-Booth motorcar, but power locks didn’t catch on as a common option until cars until 1956 when Packard included them on one particular luxury model. It’s interesting that you can still buy a 1956 Packard power door lock actuator on eBay ($9.95).
Today, power door locks are as ubiquitous as power windows, and just about anybody who has wrenched on cars has dealt with these amenities, particularly when a customer is accustomed to using the button on a fob to lock and unlock his ride. Volvo put a heartbeat monitor on some key fobs to inform an approaching owner of someone who might be lurking in their vehicle. GM has a fob for its high end SUVs that will have a liquid crystal screen that will enable the customer to remotely check tire pressures, fuel level and odometer readings, radio station settings, and more. Further, these GM fobs will have four to six times the range of a conventional fob. Power locks make us safer, and while their failure isn’t as much an irritant to most customers as an inoperative power window, they typically enjoy a fairly prominent place on repair orders when a car comes in with inoperative locks.
To troubleshoot any power door lock system, understanding that particular system is key (pun intended). In the beginning, power locks were basically reversible motors with a threaded armature that would spin around a rod with matching threads. Spinning the armature moves the rod. The other end of that rod is connected to the part of the door latch mechanism that operates the lock. Lock versus unlock is handled by simple polarity reversal, and there isn’t anything mysterious about that element of power locks unless you’re electrically challenged.
Troubleshooting Older Systems
On the older systems, power lock switches were a lot like power window switches – positive and negative feeds to the switch are delivered to the actuators with first one polarity and then the other when the switch position is changed from lock to unlock. positions.
To troubleshoot those, you check for power and ground at the master switch first, and if you have good voltage there you connect a test light or a meter in parallel with the lock actuators at an easy access point (check the schematic and test at a point downstream of both switches, since they’re wired in series), operate the lock switch, then look for battery voltage. If that’s good all the way to the actuator, look for problems with the actuators themselves. They fail fairly regularly. If the light or meter reads substantially less than battery voltage during your test, use your electrical know-how to determine whether the missing element is power or ground. Both sides of the actuator should show ground with the switches at rest. If the passenger switch is the only one that doesn’t work, realize that a bad driver side switch can have corroded normally closed contacts and prevent a passenger side lock switch from operating, so disconnect the actuator to break the circuit loop and, with all switches at their rest positions, check for a ground at both connector terminals on the actuator side of the switch. If one side is missing a ground, check both feeds coming from the driver side switch. If that ground is still missing, check that circuit feed at the driver side switch. No ground? That’ll finger a bad switch. If the ground is there but isn’t at the passenger door switch you have an open circuit between the two switches.
The BCM Factor
Today’s power locks are computer-controlled on most higher end cars, with the Body Control Module (BCM) receiving inputs from the door switches, external key pad, or the fob. With the BCM a part of the picture, snazzy things can be programmed in. Example: The door locks can be locked either when the vehicle is shifted into drive or after a certain road speed is reached (15-20 mph). Another cool deal is that if the BCM knows the airbag has been deployed, many of the modern platforms will unlock the doors to allow egress for first responders. Furthermore, if the BCM sees the key in the ignition and an unwary driver locks the doors and closes the driver’s door, the BCM will unlock that door to prevent a lockout. Ford Taurus and Sable have had that function built into their GEM modules since 1996. Ford’s GEM module did the job for awhile, and the latest Ford vehicles use some of the circuits in a Smart Junction Box (a fuse panel with a built in computer) for door lock operation. In a similar fashion, late model Asian vehicles typically have the door lock relays built into the fuse panel so the fuse panel needs replacing if one of those dandy little relays goes south.
Some 2004-05 model Chrysler Vans have a programming error whereby the door locks can simply stop responding. When I scan tool one of those vehicles, I notice that the BCM is receiving commands from the switches and the fob but it simply won’t operate the doors, not even when commanded to do so by the scan tool Active Command function. Removing the battery terminals and shorting them together to reboot the door locks typically straightens that mess out, but the Chrysler folks recommend a reflash.
The 2006 Sonata
This Korean made Hyundai Sonata was built about 80 miles north of the place where I work, and when the door lock function went away, we dove into the factory shop manual looking for answers. What we found was a BCM that takes input from the switches (0.6 volt is fed by the BCM to each side of each switch, which shorts the voltage to ground with switch operation), then the BCM triggers micro relays in the interior junction box/fuse panel to drive the locks. The BCM also knows if the actuators are in the lock or unlock position, even if they were operated by hand (most modern systems are designed this way). Well, the scan tool showed us everything was copasetic regarding the inputs and BCM outputs. The BCM was fully aware of lock and unlock switch inputs and was actually sending commands to the appropriate relays in the junction box whenever the lock or unlock switches were activated.
There were times when the door locks would actually try to work, so in obedience to the infinite wisdom of the Hyundai service engineers, we removed the junction box. The shop manual gives no instructions on how this is to be done, by the way, and it’s something of a pain to get if off. The knee bolster has to be removed along with several screws securing the panel. There are a half-dozen or so wire connectors that have to be disconnected (some of them behind an annoying plastic cover that can’t be removed until the box is unbolted). Well, we finally got it off and bench tested the box using the wiring schematic and common sense. Our investigation seemed to indicate that the relays were all functional, so we were done with our bench test and we reinstalled the panel.
The first time we operated the locks after reinstalling the panel and reconnecting the battery, some of the locks worked on the initial attempt, but they wouldn’t work the second time. This led Amanda to remove the passenger side door panel for access to the wires that lead to the actuator in that door. Using some EZ Hook ® probes, she accessed the wires and we connected a meter, which showed 11.4 volts being delivered to that door on the lock AND unlock commands, yet the actuator was largely unresponsive. System voltage was 12.4 volts – we were losing a volt somewhere. Connecting an OTC Solarity scope to the two EZ Hook leads, I selected a couple of channels and operated the locks – the trace showed that the polarity was switching nicely, but lock operation was nothing more than a mild bump – sometimes one door or another one would lock or unlock but that was the exception rather than the rule. Since both legs on the actuators are grounded with the junction box relays at rest, Amanda disconnected the door harness connector and we delivered voltage straight to the actuator – it operated very crisply.
Final analysis revealed voltage drop somewhere inside the junction box. We didn’t catch this on the bench test because we were using a low impedance test light to test the secondary relay circuits, which wasn’t adequately loading the relays.
Calling the local Hyundai parts department, I was smacked with a $747 price tag for the junction box.
The practice of building relays into the junction box is becoming more common than ever before, thus the cost of junction boxes (particularly ‘smart’ junction boxes) is rising exponentially. What each customer has to decide is how much their door locks are worth.