In an effort to avoid a Mr. Goodwrench $85 diagnostic fee I am trying to track down this issue my self. 75% of the time my 4x4 works flawless. like any would. The other 25% of the time is a different story. I can be driving down the road and all of the sudden out of no where, ALL of my ATC lights will light up including 2, 4hi, 4lo, 4auto, and Neutral. While this happends my service 4x4 light sparatically flashes on and off and I can feel my blazer shifting or at least trying to shift in and out of 4 wheel drive by its self. During this time I can push whatever button I like on the 4x4 selector and it willsimply ignore all of mywishes. My PCM doesnt like thisso I puts my engine into a limp mode where if IFLOOR the gaspedel my RPM's will not rise above 2,000.I have taken my switch out of the dash and I can still feel it doining it so I figure the switch is NOT the issue.Possibly my$$transfer case controle module$$ under my dash? any way to test it? Or.... Any help would be GREATLY APPRICIATED!!
Michael

 

If you have the service 4wd light, then you have the Auto4wd option. The difficulty here is to properly diagnose the problem, you need to have a high feature scan tool that can communicate with the transfer case control module.

I would remove the TCCM and clean the electrical connections. The TCCM is located behind the passenger side kick panel.

 

Thanks Kyle,
I just cleaned as well as snugged all the connections in both plugs to my TCCM. It is still doing the same thing. I dont understand it?? I can be in park and it will start acting up... and then quit. Someone mentioned possibly replacing my vaccume switch or actuator but I dont see how it would be causing the issue. Possibly the switch... I dont see the actuator having a mind of its own? Any thoughts? I guess I may have to take it to the dealership bucause they are the the only ones who have the tech 2's around here. And your right I don't think your standard OBD-II scanners will read the 4x4 codes...
Michael

 

It is definitely an electrical problem. The next thing I would try would be to remove the switch, disassemble it, and clean everything inside. If that does not help, then it is time to get it properly diagnosed. You could spend a lot of time and A LOT of money throwing parts at this problem.

I definitely know that standard OBD2 scanners will not read the TCCM. You have to have bi-directional controls and the appropriate "package" to be able to read the TCCM with aftermarket, high-feature scan tools.

 

Ok, thanks I will take a closer look at the switch and if I have no luck I will just take it down to the dealership. Thanks for all of your help.
Michael