Hello fellow Toyota fam and to anyone who is reading this. I apologize if I am not posting in the correct area, I am new to the Forum. Well I bought a used 2002 Toyota 4Runner 4X4 that the owner was selling because of a transmission whine. I knew that I would end up changing out the transmission when it decided to go out. And what do you know one week later the transmission whine turned into grinding sounds and eventually it threw a check engine light for P0770. I ended up choosing to have the current transmission rebuilt instead of ordering a reman. After pulling the transmission out of the truck, I removed the torque converter from out the case. Once I pulled the torque converter out I realized that the oil pump bushing had been pulled out and was stuck to the shaft of the converter. I took the transmission down for a rebuild and they ended up ordering a rebuilt torque converter, new OEM flex plate, replaced the clutch packs , bands, solenoid SL or E, oil pump, and was told that they installed a updated shift kit to my valve body, plus a radiator flush. Unfortunately I tossed out the bag of parts that they gave me back, so I have nothing to look back on. I put the transmission back in and everything was working good for just over 1,000 miles, everything felt fine with no issues. One day while driving on a long trip the check engine light came on and threw me into 3rd gear limp mode. Low and behold it was the P0770 code of shame. I cleared the code and ever since it has repeatedly come back on intermittently. It usually takes 100-200 miles or more of driving before the light will come on. This only happens at freeway speeds and one occasion where I was driving up a hill. I used my friends Toyota scanner and I was able to activate on and off the lockup solenoid, and see that lockup was not slipping and that the transmission was shifting through every gear with no problems. One thing that has my attention is that in two different situations where I would press the ETC power switch, almost immediately the check engine light would come on. I had to press the shop to start off by replacing the shift solenoid E. That did not fix the problem and the shop is trying to tell my that its an electrical issue. I have no bad transmission symptoms, and it seems to drive fine until the ECU detects a problem and throws it in limp mode. Ive done a lot of research and my heads been killing me. IM not sure if my ECU needs a reprogramming since there was a TSB for this Code and my vin falls under that, but why would it not have thrown a code sooner, mabe I need to clean the wiring harness and check my grounds, and test the continuity from the ECU to the Transmission harness of the solenoids. I appreciate anyone that has stuck through this and any answers are much appreciated.

My 1st thought would be an issue with the valve body, what updated shift kit did they put in...? maybe some crap didn't get clean out of said and is blocking a passage? Wouldn't hurt to take it to another shop and get their take on how the trans is functioning. This are all just ideas, starting points, not saying this is ur issue

I have a very similar story with my '02 however the code only comes up about once a year for the last 3 years after my rebuild with it also happening after pulling a steep hill or similar high load condition to my memory. One similarity is we both had updated shift kits/valve bodies added. I haven't worried too much about it due to the infrequency and it driving perfectly fine after clearing the code but I figured I'd comment for the bump and to track any solutions in case mine ever starts showing up more often. Best of luck to you my friend!

I am fighting a P0770 nightmare. Shift solinoid keeps failing causing the TC to not lock up. Replaced 3 times. Last a couple days then fails. Shop doesn't know how to fix it. I will have to take it somewhere else.

Is the TC releasing when it needs to come out of lock up? You can test it by getting up to 55 mph. Keep your right foot on the throttle maintaining speed, tap the brake pedal with your left foot and watch the tach. It should jump up 200 or so rpm. If it usually occurs climbing a hill try to hit the OD button to drop down into 3rd and see if it will still throw the code.