Background: '02 4x4 auto overhauled at 108,000 due to Overdrive gear failure. Torque converter replaced with non-o.e.m (brand really not known, part # 'cont 027-20'). Failure and overhaul was away from home so returning to independent trans shop is difficult. For about a week or ~400 miles after the repair all was well with no bad behavior other than a very slight vibration in the floorboard which was marked up as being hyper-sensitive following the R&R.
DTC p0770 began to show up every few days then proceeded to occur on every 2nd trip with pending on the first lock-up call. I dropped the trans pan which was very clean with no trash on magnets, removed and tested the solenoids, douched the valve body, and found no debris. I returned it to shop and left it for a week. During this week he tested all the solenoids, confirmed all the signals. Still trowing the code he then replaced the valve body and all solenoids.
It is still throwing p0770 errors as soon as it gets the lockup signal. I've backprobed the ECU and have an LED out to observe the lockup signal. I've also had a meter at the trans case junction to rule out a harness problem. Right now I'm thinking it's a torque converter issue.
The shop that did the work is reluctant to pull the trans again to replace the converter as an experiment. They also keep pushing for an ECU reflash based on an old TSB. I've resisted since the existing ECU was quite happy for >100k miles and no one really knows what the reflash does.

Would someone please observe their tachometer as the torque converter locks and unlocks. The unlock is easiest to do. Traveling at >52mph steady speed, steady load, depress the brake pedal just enough to trip the brake lights. This will unlock the torque converter and you will see an engine RPM increase. I'm seeing about a 220 rpm increase at about ~55mph.
The point of all this is to determine if my torque converter is fully locking and the 220 rpm change is about right, or if I'm only getting a partial lockup.
The detection of the error is really fast. When the LED lights at lockup signal the Check engine light will come on with 1 to 2 seconds. With the quickness of the error from command to trigger I'm wondering about a lethargic lockup clutch in the unknown brand of torque converter.

If I could find a torque converter easily I'd just change it myself, but dang these things are hard to locate at other than the dealer. The two sources I've found want the original to match to as there seems to be several 3.4 to a340F versions. Toyota locals all want ~$800. AutoZone lists one for the 340H but a call to pro-king could not verify fit, with a 'probably not' answer.

If anyone knows the specs for the 00/01/02 converter that would help too.

 

I did this test for you and in my 4runner (1996, 4x4 auto, 3.4 L) RPM increased was about 190 RPM. Hope that helps.

 

Thanks for the reply. I'm thinking that the lockup test for DTC is very time critical. One way or the other I'm afraid that I'm gonna have to replace that T/C this information just makes me more comfortable waiting 'til I can find a deal.

 

I know a guy in SC that rebuilds torque converters, probably in the $150 range.

 

I've never heard of this for a Toyota, I don't think it's even possible on a Toyota ECU. Ask to see the TSB.