2001 Forester: Blinking AT Oil Temp light

[MEL79000]

Howdy All,
I am dealing with a blinking AT Oil Temp light and am interested to hear if anyone has any thoughts as to what may be wrong. Below is all of the background information to date.

1. The light first came on after driving 100+ miles on a rough (washboard) dirt road.
2. There is absolutely no difference in how the car drives.
3. The diagnostic trouble code is 77, which is for the lock-up duty solenoid.
4. My mechanic recently dropped the pan and said all the solenoids look fine. He replaced the fluid and filter and buttoned her back up.
5. I took a drive to the mountains the other day approx. 1.5 hours of mixed highway and backroad driving. On the drive to the trailhead there was no light. Hiked for around 5 hours and drove home. After around an hour the light came on, while on the highway. Again, there is still no change in how the car drives.
6. I spoke with my mechanic today and he thinks there may be some temperature sensor that is damaged. He is confident that if the lock-up duty solenoid was busted I would definitely be missing my overdrive and would notice the difference.

It is a big mystery at this point, so any thoughts would be helpful.

Thanks for your help!

[Gloyale]

Did the the "mechanic" test the Lock-up solenoid?  Like ohm it out?

 

There is a temp sensor in the trans, but if it was that the light would come on solid not blinking.  He could have tested it with an ohmeter.  Not sure this guy really is the right one to work on this for ya.  If all he did was drop the pan and look, you paid for alot of nothin except new fluid.

 

You wouldn't lose "overdrive" since these cars just have a basic 4spd trans.  you still get all 4 gears.  You could be missing the lockup and not really notice the extra 500~700 rpms your running on the highway.

Edited October 26, 2017 by Gloyale