Service 4WD Message

My 4X4 switch has a mind of its own it seems .... sometimes comes on in ANY position after starting truck, sometimes doesn't come on at all!!!! Any bright ideas out there??? I looked at all the posts about the switch and even resoldered connections, but still have same problem

Okay, so this goes on, and on and on ..... I have a leaky/noisy differential & lots of metal in my fluid :frown: So I am going to attempt surgery and got myself a used differential with less than 10K on it ). Now this is my first attempt at drive train, and have been reading the GM shop manual, that tells me to mark the shafts before disassembling .... Can someone tell me why?? As I am not putting back the same part that came out, so how does that matter????? :frown:

You obviously have some mechanical issues that need to be dealt with that may or may not be related to your 4x4 switch. A couple of months ago, with about 200 miles left on my warranty, my switch started doing the same thing as yours. Service 4WD message would come on and no lights would be on in the switch. Other times, I would start my truck and everything would appear to be working fine. Took it to the dealer and they told me some kind of electronic module was failing. Woulda cost me $500 had I not still had my warranty. Just something to think about. Might want to have your codes read.

Do you have the paperwork that shows what they replaced? I have had both the push-button switch and the ECM checked (by using someone else's as a test) and still have same problem.

I think that next step is to check the sensor connectors on the Transfer Case, or possibly the sensors themselves .... If anyone knows which sensor is what, and how to best approach the cleaning, IF they are corroded or wet, I would appreciate that kind of info. I have also read that it is possible for the ignition switch to NOT be sending out correct voltage and causing the problem as well. I do have a DTC C0327 .....

So next steps are:
1) checking the sensor wiring connectors to sensor
2) replacing sensors (part number & which one?)
3) Encoder motor troubleshooting .....

Most likely your switch probably needs replacing.

I used a switch from another truck and same problem .... so I don't think that is it.

Man, I looked and looked and I apologize but I cannot find the repair paperwork. All I can tell you is that it is some kind of electronic module relating to the transfer case... while it appears that it is the switch that is malfunctioning, it is NOT the switch. The part itself cost somewhere around $400.

In the meantime, I'll keep my eye out for the paperwork.