Service 4wd Message

[Eric Pylant]

Thanks for the follow ups! Keep updating us!

I'm having a similar issue. The 4x4 works when it works (usually after re starting the car) but the buttons seem to illuminate randomly and some times never at all.

A couple times I have shut the car off in 2hi and minutes later restart it and it's in 4Low. I'll switch it back into 2H and it makes all the clunks and noises so Im sure the transfer case motor is working, it's just weird!

And sometimes, after cycling between 4H and 2H a couple times, the computer seems to get confused and displays the service 4wd light. IDK.....

-Eric

 

[Jenzenauer]

I guess I owe another update on this. I have not been back to Dealer as it never has a problem during dealer hours so I can take it there while the code is actively displayed. @Eric Pylant Your problem sounds identical to mine sorry I cant help yet. I did watch a youtube video from a user I cant remember about tracing down a ground fault that was located on the solenoid on the from diff between there and up near the fuse box under the hood. He ran a jumper wire from end to end and did not bother replacing the broken one. So that is my next plan to try to find a possible broken wire in the circuit but I have not had a chance and with the Wisconsin weather I am not planning to lay in the snow and ice to do that so maybe in the spring. I will update as I know more and if I find anything.

 

[rzabel]

Here's a scary update on my situation. After experiencing all the same random issues identified in here and having 4 encoder motors installed, fixing all grounds and replacing the switch, the dealer finally told me the problem was the transfer case. $2800 later I'm finally using 4wd with confidence.

 

[Jenzenauer]

Well that is a very scary thought. I did not have many reoccurrences over the summer months how ever Tuesday night as I am leaving the bowling alley I start my Tahoe up and the truck is in 4-Low which normally I am able to shift to N and press the 2wd button and it will clunk and shift back into 2wd. How ever this time it immediately flashed the Service 4wd message and the Traction Control Disabled message now I know the TCD message is normal when in 4-Low but I am unable to shift as the Lights on the switch were all off. I cycle the power on and off a few times shifting through the gears and nothing helped. The truck was in 4-Low as I drove it across the street to a gas station. I continued for about 20 mins starting and stopping playing with the gears and nothing helped. I then pulled the 15 fuse out of the 4wd slot on the in cab fuse panel. Started the tahoe up with out the fuse and it did nothing different. I also cycled thru the gears and cycled the key on and off. Turned it off and replaced the Fuse. Started the truck up and the Switch lights were back on and I was able to select 2wd and it shifted with a clunk like normal in N position. So far no further occurrences. Not a fix be any means but it got me home. I will test this method the next time it acts up and see if this can be duplicated.

 

[S33k3r]

There are, essentially, 3 pieces to the 4WD system -- aside from the grounds, of course!!! The push buttons/switch, the encoder motor, and the transfer case itself. From what you describe, it sounds like either your switch is going out, your encoder motor is going out, or you have a ground problem.

As an example, the previous owner of my '04 Silverado had a mechanic tell him the encoder motor was bad -- they replaced it. Then they decided it was the transfer case -- they installed a rebuilt unit. Finally, they replaced the switch, and his 4WD problems went away... I do not know his symptoms, he just related to me why those components had been replaced/serviced. It was a boon for me, though.

 

[Fless]

There are, essentially, 3 pieces to the 4WD system -- aside from the grounds, of course!!! The push buttons/switch, the encoder motor, and the transfer case itself. From what you describe, it sounds like either your switch is going out, your encoder motor is going out, or you have a ground problem.

As an example, the previous owner of my '04 Silverado had a mechanic tell him the encoder motor was bad -- they replaced it. Then they decided it was the transfer case -- they installed a rebuilt unit. Finally, they replaced the switch, and his 4WD problems went away... I do not know his symptoms, he just related to me why those components had been replaced/serviced. It was a boon for me, though.

The fourth essential piece is the Transfer Case Control Module under the dash....

 

[S33k3r]

Oh great. Another part I'll need to replace... LOL.

 

[Jenzenauer]

Yeah at least for mine I have Replaced the Switches which originally were bad based on the ohm meter readings. I then replaced the Encoder motor with a off brand, next I removed the main ground wire on the frame rail and cleaned all connections and painted over once installed. I then took to the dealer and then said the encoder motor was the issue so I replaced with GM part and then did a reflash on the TCCM which they found an error in the programing or something. It worked for a short while after then started up again. I have not had a chance to do anything further on it yet. Since I pulled the fuse to get it to shift the other day when stranded I have not had any further issues but I am sure it will in time.

 

[Jenzenauer]

Does anyone have a good schematic or pictures that shows where each ground is that could have an impact on the 4wd system?

 

[Hobert]

Here is a ground schematic. I can get you a higher resolution.