A343 Sometimes dos't lock Torque Converter.

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C

cantabkiwi

10 Year 15 Year
Joined
Jul 6, 2007
Threads
10
Messages
23
Location
CHristchurch New Zealand
Hi

I have a KZJ78 with a A343 auto in it.

It was rebuilt 2 years ago after i got water in it. I have a cooler in front of the radiator and a temp gauge on it. I have by passed the cooler in the bottom of the radiator. It has been good since the rebuild and I have not changed anything in the last year or so....

On my last two trips out of town I have been doing some hill and 4X4 work then out onto the flat for the trip home. The Auto has cooled down to about 70 c or so. Then it has started not locking in the Torque converter in 4th. I have then turned off /on the overdrive button a few times and eventually the lock up has started working properly. It kept working for the rest of the drive home. I drive with the Power button off.. I also has the ECU caps done about 3 years ago...

The Trans Fluid is still good color and doesn't smell. I have removed the power and disconnected the ECU last night. I will go for a drive in the weekend and see if it improves....

Any other ideas?

Thanks
 
I have a similar problem in my LJ78 A343f. After about 15-20 minutes of driving, once the transmission is warmed up, lockup disengages in 4th, but it still works in 3rd. Trans fluid and screen were replaced 25-30k kms ago. At first I thought it was an electrical problem connected to the brake wiring, but the fact that it only happens once the trans is all warmed up makes me think that it is inside the transmission. So far I haven't been able to figure out what causes the problem; did you have any better luck?
 
The lock up is electrically controlled by the ecu. There is a solenoid in the box.. It is activated when a number of conditions are met, Water temp is hot, speed is correct versus throttle position.. Thats all done by the ECU.
So a few sensors could have issues... Another check would be to wire in a test light into the wires that feed the solenoid and confirm its getting a signal... If it is getting a constant signal then the solenoid could be playing up. They sometimes get sticky or could leak past the o ring.
Have a read of the article on how the ECU controlled Toyota's work.
http://www.autoshop101.com/forms/h16.pdf
 
Thanks for the info, I will have to give that a read. When you say the solenoid is in the box, I expect that means in the transmission.
 
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