Yes, there are OBD2 codes for shift solenoids. If there’s no drivability issues, then it might be the torque converter lockup solenoid.

Hard to say why they fail. Could be lack of fluid changes. It’s not so common that I’d replace them on a schedule like plugs.

 

Thanks. How does the torque converter lockup solenoid work to bypass that problem?

 

It doesn’t.

The purpose of that lockup clutch is to eliminate torque converter slippage. It locks up at speeds higher than 45 MPH. So you should see an RPM drop of about 300 when it engages. If that solenoid is bad, it won’t lock up. That’s why most people won’t notice it’s not workin. It’ll cost you a bit of fuel mileage is all.

 

Thanks. Is there any engine or transmission damage from having that solenoid faulty and the seller keeps driving it?

 

I had a no 2 shift solenoid fault code for several years on my 93 (OBD1) before the car went wonky one day and flashed its OD off light at me an wouldn't shift. I had the replacement solenoid from junkyard ready to go, dropped the pan and swapped it in and it ran another 5 years trouble free.

 

Shift solenoids on the A140E are very reliable...the few times I've seen codes the trans fluid was very old. High chance that swapping out a lot of the fluid will unstick them; not so with Shift Solenoid SL (the torque converter lockup solenoid). That one has the highest failure rate (and that's still absurdly low). It's mounted to the outside of the trans case, toward the front of the vehicle; just grab another from the junkyard and make sure to get the o-rings for it from the dealer.

As always read the codes to point yourself in the right direction. There is no generic "shift solenoid" code, there are specific codes for each solenoid.

 

I had been looking for the location and purpose of the SL solenoid all over the internet. Thanks for the gem of information.

 

Another thing that can cause weird shifting is burnt sensor wires. When an engine is swapped, the wiring can be disrupted, drop onto the EGR pipe, and burn through. This happened on two of the five I've owned. To check if the original engine is still there, check the tag located at the pan rail opposite the starter. It will have a VIN on it, if original, it matches the car.