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Check engine light - 2005 Corolla 4 cyc, auto, transmission code

This is a California car that won’t pass smog tests with a lit check engine light. I don’t know the specific code, but the description is that the torque converter is staying in the “off” position. Apparently the lock up torque converter is part of the emissions system in that if the torque converter does not lock up then the rpm’s are higher and that produces more pollutants.

1st step was to flush out the transmission and the flush made sure all the fluid in the torque converter was removed and replaced. After that was done the trans fluid has stayed nice and clean and pink for about 400 miles. The CEL was turned off after this service but came back on in a few days at about 200 miles. Next, the solenoid that activates the torque converter was replaced. The CEL was turned off again, an this time the CEL came back on after a hour of driving on local errands.

Me and my generally good mechanic are hung up now. We were betting the solenoid change out would solve the problem. Any ideas out there? It seems that the torque converter is in fact operating properly. The tranny shifts smoothly and the rpm’s drop at the proper times indicating the torque converter is locking up.

What’s the code? It should be written on your copy of the shop order.

I don’t have the specific code. Son is driving the car back to CA and we will have to deal with the CEL in the next month or so to get a passing smog test. I just wonder if putting in a new torque converter will do it? Or just be more parts replaced without resolving the real problem

without the exact code, you’ll be just throwing money into (maybe) unnecessary parts…wait to get the code , proceed from there…

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I’d have guessed replacing the solenoid would fix the problem too. Suggest to ask the shop to double check their work. It’s possible they inadvertently put the same one back in. Or didn’t connect up some wire or another they had to remove to do the job. Everything still looks ok? You’ll probably need to find a shop with the Toyota scan tool to further test what’s going on.

One more idea: There’s a slight chance the problem is actually fixed, but the computer is stubborn and won’t turn off that light until the drive cycle completes. While checking the engine and transmission codes , also check the readiness monitor status.