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Transmission downshifts unexpectedly

My son has a 1995 Saturn SC2 with an automatic transmission. Everything on the car works great except…

Every once in a while, maybe twice a week, the car downshifts unexpectedly. This usually happens on the freeway. The transmission stays in the lower gear even if you take your foot off of the accelerator. Stopping the car and returning to speed does not fix the problem, but turning off the ignition and restarting the car does.

Does anyone have an idea what might be wrong? I was wondering about the computer, since cycling the engine seems to reset it and nothing else does. Is there an electrical signal from the computer to the transmission in this car? Or am I on the wrong trail?

Well, it could be a number of things causing this. This transmission is electronically controlled. It could be something as simple as a faulty TPS on the engine. Since its not happening very often you might have to wait until it gets a little worse unless you can leave it with a shop.


TPS = Throttle Position Sensor.