P1605 Transmission issue

[jcarringer]

Hey everyone,

Just got a P1605 code today and having some problems with the transmission on my 2001 Pathfinder. I think it's in failsafe mode because it won't shift out of 2nd or 3rd gear. It struggles to start out like it slipping but I think it's in 2nd or 3rd gear all the time. O/D light doesn't come on either when the button is pressed. When I get up to speed and release the accelerator RPMs drop and it wants to shift to a lower gear but goes back and forth between 2nd and 3rd. Research indicates the ECU can't talk to the transmission so I'm thinking maybe the TCM. What do the pro's on here think? No fuses blown that I can see but I might not even be looking at the right fuse.

Also which side of the drivers bay is the TCM on? There was a post I found on the Internet that said right side (me in the drivers seat) but the Haynes Manual I have, says left side. The Haynes says the PCM is on the right side. Just looking for clarification.

Also final question, doesn anyone know the real part number for the TCM unit?

Thanks all for the help

[jcarringer]

Update: I found out the part # 31036 4W000 for my Pathy 2/00 manufacture date and location of the TCM (left side). I'm thinking about getting a salvage part from the Internet. I can't swallow $400 for a non-returnable part if it doesn't fix the problem. There are some variants of the part 4W001 and 4W002 which correspond to post 4/00 manufacture date and different years. Anybody know if the 4W001 would work? There were some issues with the 4W000 with floating between 1st and 2nd so I'm hoping that is fixed in 4W001 as well as the 4W000 are harder to find but I want to make sure I'm not going to create more problems.

Finally, can I drive the car while it is in failsafe mode while the part comes in? Basically it's stuck in 3rd gear and this is mostly highway driving so not alot of stop and go

[jcarringer]

Final update: Replaced the TCM (probably the easiest module I have ever replaced on my Pathy) and it fixed the problem.

[Mikey178]

I had a similar issue where my truck would go into fail safe mode. My solution was to changing all the drivetrain fluids (Front diff, rear diff, transmission, transfer case) and i've been good since but I will keep you solution in mind next time if the issue ever comes back.

Thanks

[Green Pathy]

how do you replace the TCM? Where is it located?

[jp2code]

how do you replace the TCM? Where is it located?

Yeah, same here. Sure would have been nice if the original poster had bothered to come back to help others.

[mdmellott]

how do you replace the TCM? Where is it located?

A/T Control Unit located just to the left of the data link connector under the dash on a '96 Pathfinder. Simple component removal. (see page EC-238 of the FSM) https://www.nicoclub.com/service-manual ... 6%2Fec.pdf

[mdmellott]

Yeah, same here. Sure would have been nice if the original poster had bothered to come back to help others.

Under the front passenger seat on a '94 D21, if that's what you're asking about. (see page AT-34 of the FSM) https://www.nicoclub.com/service-manual ... 4%2FAT.pdf

[jp2code]

Yeah, same here. Sure would have been nice if the original poster had bothered to come back to help others.

Under the front passenger seat on a '94 D21, if that's what you're asking about. (see page AT-34 of the FSM) https://www.nicoclub.com/service-manual ... 4%2FAT.pdf

Thanks! It was actually for my 2000 Xterra, and I found it. It's under the dash on the LEFT side of the wheel well.

In fact, my whole problem turned out to be that the 15 amp fuse going to the automatic transmission was blown. I'm not sure what is making that fuse blow, but when it happens the truck turns into a brick.

[VStar650CL]

There's a bit-bang "diagnosis line" between the ECM and TCM on most of the pre- and early-OBD Nissans, and P1605 is basically the ECM saying, "Hey, looks like the TCM is dead." Which of course it is if the TCM fuse is blown.

The two most likely causes of a TCM fuse blowing repeatedly are degraded wiring inside the transmission or a solenoid with degrading coil insulation. The former can usually be repaired DIY if you can locate the problem, but that generally requires dropping the Valve Body. The latter can generally be identified with an ohmmeter, just look for a solenoid with substantially less coil resistance (DCR) than the others. Individual solenoids for early models are generally available as repair parts, at least from the aftermarket if not OE.