My case, the SL solenoid (i guess called Solenoid A) malfunctioned, which triggered the check engine light and put the car into limp mode. After letting it sit for about an hour, the shifting returned to normal — however, my scanner still shows the SL solenoid not switching (ON/OFF). The ST solenoid is functioning fine, and the SLT is also working as expected. The scanner also showed that when you put the car from Neutral to Drive, it first shows up 3rd gear and soon switches to 1st gear. Further indicating the issue with SL solenoid, the 3rd gear show up is due to SL not working, but the pressure difference detected by ECU switches to 1st. Just my hunch, not sure if it works this way or not.
Last week, since we couldn’t find a replacement part, we removed and tested all the solenoids individually. All worked properly except the SL one. We cleaned it thoroughly and replaced the 38k-old ATF fluid (which was brownish, unfortunately). The scanner showed all to be working fine.
The car drove fine for about a week, but the check engine light is back again.
So, I have a few questions:
Since replacement solenoids available here are used, what should I check or test before installing one?
Is it better to replace all three solenoids together?
Is there anything else I should look into — maybe calibration, reset, or other checks?
For reference:
Car: 2015 Corolla GLi Auto
Mileage: 138,000 km
Location: Karachi
Also the code was P0974
After a week or so,
Got the transmission valve body opened again, it had same error.
Filled new transmission oil a week back. It was pretty bad this time as well.
Found new (kabli/used) soleniods, will fill in new fluid again and also asked to change the filter as well.
It is decided to change the oil after a few months again.
Could this new fluid getting bad means there is something major or just solenoid and filter change would be fine?
I am not interested in flushing the transmission with any flushing fuild, Max I would do is flush using a new transmission even if it means doing it twice right now. I mean use two new fluids one for flushing/draining and one for refilling.
Thanks in advance for any help or insights!
