Driving a 1999 Infiniti I30t. Cruising along on the highway, my cel came on. Came home, checked the codes and I got a P1605 - A/T control unit or circuit fault. (Also have a p0325 - KS code, but that's old and unrelated). Transmission seems to be working just fine, but I want to be sure. It's my wife's car and I don't want her trash it accidentally.

This code is not in the 1999 I30t Service manual from nissan, but it is in the Maxima haynes manual. Searches on the org identify the most likely cause to be a connection problem between the TCM (Transmission Control Module?) and the ECU.

There is not a whole lot of info for this code to be found.

Does anyone know where the TCM is located and/or the harness used to connect it to the other systems? I can't find jack about this in the haynes manual. I want to check/clean the contacts in the harness first to see if that resolves the problem.

Also, any way to test the TCM to see if it is bad?

Thanks!

 

Your TPS is a communication link between the engine and tranny. I also recently had a tranny communication fault code that vanished after I replaced my TPS. Might not be your problem, but It's easy to test. Great idea to test the TCU wiring but I have no idea where it's at.

 

TCM location:


The wiring harness for the TCM is a part of the engine wiring harness.

P1605 shows up in the '99 I30 FSM, just look for P0600; they group the two together.