Hi Richard, I'm having a problem with my late 90s model GMC suburban,
automatic transmission. I had the oil changed 2 days ago. The day before
this, I began having the problem. When I was driving the vehicle, it starts
just fine but then instead of changing gears it stays in first gear and the
RPMs just increase. The speed gradually increases but you can tell its still
1st gear. I've checked all the fluids and everything is fine, it was low on
coolant so I added that. Any ideas before I take it somewhere?

Thanks,

Jon

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The transmission control part of the PCM either doesn't know the vehicle is
moving or there's something stuck or inoperative in the shift circuits.

I guess the speedometer works?

Have somebody retrieve the trouble codes - write them down.

Then remove the battery cable for about ten minutes.

Put it back on (reboots everything) and see if that makes a difference.

Let me know what happens

Richard

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Richard,

Thanks for your help. Your advice was right on point. I really appreciate your help

-Jon