68Datsun510

Hey folks, sorry for multiple threads about different issues regarding transmission codes , has anyone ever felt like these computers are a little paranoid in these vehicles? Because I was accelerating three-quarter throttle uphill and it threw a P0740 transmission torque converter clutch lockup code, less than two seconds later when I backed off the throttle I watched it lock up perfectly. so it's flagging it as having a problem when it's behaving perfectly normal...

This code coming after I have done every step in the diagnosis of the P0740 code , cleaned neutral safety switch, cleaned all connections leading to transmission, new and properly adjusted brake light switch, new throttle position sensor , Recently had transmission serviced for new filter and fluid.

Running out of ideas here but to believe all the transmission shops insisting that at $1200 worth of new parts will solve the problem

mlepesant

i had been dealing with similar issue and same code for over 2 years. new NSS, solenoids, valve body, TPS and hours trying to diagnose. Finally i was really tired of it so decided to buy a used transmission. $250. I didn't know the AW4 could shift that well... Hopefully it will last this time.
Engine is running great with 350k miles on it. Transmission has been a different story ever since I got the car. Rebuilt at 90k (I bought the car with $85k), rebuilt at 200k, struggling for the past 30k miles at least with this code and finally bought the used one that I installed with a friend.
Anyway sorry... not very helpful but despite many attempts and great help from this forum I couldn't fix it.

CCKen

Your '98 (I think) AW4 has an Input Speed Sensor.


TheTCM uses the Input Speed Sensor (ISS) to detect transmission solenoid functional faults (P0751 solenoid A functional fault, P0756 solenoid B functional fault, TCC solenoid C P0740 functional fault).


Because when you torque the engine ("Because I was accelerating three-quarter throttle uphill and it threw a P0740 transmission torque converter clutch lockup code, less than two seconds later when I backed off the throttle I watched it lock up perfectly. so it's flagging it as having a problem when it's behaving perfectly normal"), there may be a wiring problem for the ISS, triggering a 740 code, when the engine torques it may be pinching/chafing a solenoid wire, then when you let off the gas the engine torque goes away and the solenoid wiring returns to normal.


Examine the wiring where it goes down towards the transmission by the transmission dipstick for chafing and under the Jeep near the .


Area near dipstick:




A view of the left side of a '98-'01 AW4 showing the ISS and the solenoid harness. harness
.