Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

3rd gear shudder after ECM replacement

I recently had a new Idle Air Control Motor replaced in my '92 Olds Ciera due to stalling. The mechanic told me I also needed a new ECM because the original one wasn’t communicating with his diagnostic machine. So he put a used ECM in my car. When I drove the car home, I noticed it was shuddering in 3rd gear. Took it back to the mechanic and he said I probably have a transmission problem. He recommended the shudder fixx, and I did that, but to no avail. I believe the problem is the used ECM. Could it be not communicating with the solenoid to tell the TCC when to lock/unlock? Is there a way to test or “fix” this ECM? Or maybe get another one? Car shifted GREAT before I took it to the shop. Many thanks.

Does your Ciera have the L4 or the V6? Is your transmission the three speed TH-125 or the four speed 440-T4? I assume that the PROM or EPROM was transferred from the old ECM to the new ECM. If this ECM has the EEPROM soldered into the mother board, was the replacement ECM flashed with the correct data for your cars configuration?

Help us help you.

Have him put the old one back in and see if the problem goes away.

The TCC solenoid is operated by a driver within the ECM. It could be this driver is faulty in the replacement ECM.


It’s the V6, 3.3L, and three speed TH-125. I don’t know if the replacement ECM was flashed w/correct data. I tried talking to the mechanic about this, and me being a woman and hardly able to say the right thing to a mechanic, he told me I’m mistaken and that it’s a good ECM he put in. He also offered to flip the switch on my transmission to take away the shudder, but I know that’ll make the engine run rich. Would somehow like to get to the cause of the problem. thanks very much!

Thanks Oblivion. Well, when I brought the car back to the mechanic, he suggested I put the shudder fix in it, drive it a few days, then bring it back in if it still had problems. So I brought it back in a few days later, and asked for the old ECM back. They had thrown it away.

Can the ECM be tested to see if it’s a faulty driver? And is a faulty driver easy to replace, or just get another ECM? Thank you!

The ECM is not repairable. It may be worth putting another one in, or seeing if the existing one can be reprogrammed. It’s a pretty big coincidence that the problem started right after the replacement.