Hi all,

My transmission seems to be upshifting too early and not downshifting into the correct gear at full throttle. No codes from the ECU. I ran a self-diagnosis on the TCU, says there is a problem with the TPS circuit. I've tested 2 different TPSs, including a new one, neither fixes the problem, and both are in spec. It will start shifting correctly on rare occasions. The FSM says to backprobe the connector while the ignition is on, but the harness seems too sealed up to get a test lead in there. What should be my next step in fixing this?

 

Forgot to mention that I can shift with the gear selector just fine.

 

With a good multi meter you get wire a probe test lead to be able to probe into a wire. Fluke 88 comes with it down side is the fluke 88 is like around $400 dollars. You can probe the tps harness just need very thin like needle probes. Could also be your transmission is having flow problems within the valve body part of it. OBD1 ecu's and tcu's are dumb as a door ****. How often have you seen the check engine light come on in your maxima? I can say never on mine even though ive had my O2 sensor go out and have various vacuum leaks. As well as engine misfires. Don't expect the computer to say something is wrong often. Now one thing you could do is drain and change out your trans filter and also add a trans additive to help prolong the life of your transmission.