my truck is throwing a P0875 right now along with a 700 obviously. it also doesnt have a gear range indicater when first started, not until it throws the code. then i get a range shift inhibited message. I just had my tranny rebuilt with new altos, bearings, seals, and whatever else by my builder. i am just looking for some advice to look into it. he told me to try a new NSBU, tried it tonite and no dice. Moss helped me the other day by playing with it some more and no fix as of yet. Builder told me everything went well in the build and that the valve body looked good, didnt need to be reamed either. So waht that code tells me is to check the pressure switch assembly, or the harness inside the trans. what do you guys think? namely mike L obviously :) just seeing what you guys all think about my situation.....fire away

I'm looking at my GM book. That code PO875 is for Trans reverse pressure switch circuit malfunction! Sounds like a possible harness problem, maybe a broken wire. Book says that the TCM will freeze your torque converter from engaging. Look for a bent or backed out terminal or damaged terminal on TCM wire connection, or a broken or chafed wire inside the insulation.

Pull the pressure switch manifold off and look at the o ring at the very top. It is the furthest one from the rest. It may be cut, crushed or missing.

love your so called builders explanation. " operation went perfect but the patient died. " :p:

well we replaced they PSM and the internal wiring harness....exact same result. p0700 and p0875. so were back to square one. also, when we disconnect the maing harness on the back of the trans, it doesnt limp it how it should, like it def. doesnt go into third gear. or maybe i misunderstand how that works? either way, could this be a main wire harness issue? or a sensor issue by any chance? i guess atleast its a good thing its only one code.....................

no one has any insight?

My next step would be an NSBU switch replacement which is cheap and then if that didn't help, valve body inspection for stuck valve.

Thanks mike, i have tried a brand new nsbu swap, didnt help. the valve body didnt have a stuck valve when Al went thrrough it he said, everything moved just like it should he said....could this be a wiring issue or no?

Thanks mike, i have tried a brand new nsbu swap, didnt help. the valve body didnt have a stuck valve when Al went thrrough it he said, everything moved just like it should he said....could this be a wiring issue or no?

1) the obvious - you checked the fluid right?


2) it could be a wiring issue.

Did it work before the rebuild? You can check the electrical if you want.

First disconnect the 20 way at the trans and the Red connector at the TCM and check continuity between Pin 4 (at the TCM) and Pin K (at the 20way). Also check to make sure you do NOT have continuity to ground on this wire with it disconnected(at both ends). If you do you have a short between the trans and the TCM.

The same thing can be done when you drop the pan to check the internal harness.

To check the entire circuit pull the PSM but leave the wiring connected, provide a ground from the PSM frame to the valve body or case, then use a pencil eraser to push the pressure switch and check the continuity at the connection to the TCM between Pin 4 and ground. You should see it continuity to ground when you are not pressing the switch then an open circuit when you push down on the switch. If you see this then it is NOT an electrical issue.

Thanks mike, i have tried a brand new nsbu swap, didnt help. the valve body didnt have a stuck valve when Al went thrrough it he said, everything moved just like it should he said....could this be a wiring issue or no?I hope I dont sound like a complete jerk, but why are you having to fix this? I would park it in front of my builders shop and tell him to call me when it's ready.

I hope I dont sound like a complete jerk, but why are you having to fix this? I would park it in front of my builders shop and tell him to call me when it's ready.

X2, all builders IMHO should stand behind their work...

1) the obvious - you checked the fluid right?


2) it could be a wiring issue.

Did it work before the rebuild? You can check the electrical if you want.

First disconnect the 20 way at the trans and the Red connector at the TCM and check continuity between Pin 4 (at the TCM) and Pin K (at the 20way). Also check to make sure you do NOT have continuity to ground on this wire with it disconnected(at both ends). If you do you have a short between the trans and the TCM.

The same thing can be done when you drop the pan to check the internal harness.

To check the entire circuit pull the PSM but leave the wiring connected, provide a ground from the PSM frame to the valve body or case, then use a pencil eraser to push the pressure switch and check the continuity at the connection to the TCM between Pin 4 and ground. You should see it continuity to ground when you are not pressing the switch then an open circuit when you push down on the switch. If you see this then it is NOT an electrical issue.

will def address this. when it quit on me, it lost forward gear ranges and neutral was reverse.

I hope I dont sound like a complete jerk, but why are you having to fix this? I would park it in front of my builders shop and tell him to call me when it's ready.

X2, all builders IMHO should stand behind their work...

builder is helping me, im just looking for some more insight. its just that im an hour and a half from him so it would be a pain in the ass to trailer my truck up to him to diagnose

will def address this. when it quit on me, it lost forward gear ranges and neutral was reverse.



Definitely something in the build

Definitely something in the build

We are doing a valvebody swap on monday. have a working one out of a truck so thats the next step. Work has been crazy getting everyone ready for harvest so free time has been limited. Man oh man dont i love working at a John Deere dealership!!! :cool: But atleast i have a work truck to get me around!!

valvebody swap got it running! i dont know whats wrong with the orig but my builder will hopefully be taking care of that. alls i care about mostly is she runs again!!! today was first time ive bought diesel fuel since april!!!! haha but man oh man do the km2s look amazing