Service 4wd Message

[Jenzenauer]

2006 Chevy Tahoe 189k 3rd transmission. I am unable to find my previous post about this so just wanted to post an update. I was having the Service 4wd message and also stability control disabled sporadically. I used information on here to test the switch and indeed the 4Lo button had a bad ohm reading so I started there and replaced the switch. It seemed to help but then periodically it would come back and if I used 4hi or 4lo once I was back into 2wd it show the message every time. Next I replace the encoder motor with a no gm from the parts house. While I was doing the job I removed the ground wire/strap near the frame rail and cleaned and sanded to make sure a good connection was there as well. Once complete it seemed to work perfectly for a couple weeks then began to randomly show the message again and when I would turn the key on sometimes it would show 4lo, or 4hi or no lights or 2wd. If it was in 2wd with lights on it would shift normally but once I switched back to 2wd from 4lo or 4hi it show the message again. Anyway long story short I took it to the dealer finally. They ran the code which at the moment I dont have it to add but can later. The tech said that that code indicated either Encoder Motor error or transfer case mechanical failure. Transfer case showed no issues so we replaced the encoder motor next. As part of that a Re-flashing was suggested/required. In doing so he found a couple issues with the previous coding. There is a selection that is supposed to be A A or B B and it was set to A B so he thinks that was the root cause of the issues. SO i guess if anyone has a similar scenerio and has replaced everything I would suggest having the Re-Flash done before parts as it was only $99 and the rest was around $800 I hope this helps and thank you for all the help while working on this and input from members.

 

[rzabel]

Very interesting. I just had my 4th encoder motor replaced (two have been on warranty), so I'm definitely following this one. The last two have been replaced by the dealer, but they never mentioned a "re-flash".

 

[George B]

The switch is easy to fix if you can solder. The joints where the larger pins attached to the board break causing a bad connection. I repaired mine by re-flowing the solder.

 

[swathdiver]

Boy, my eyes won't even let me read that mess anymore.

 

[Jenzenauer]

So update: The repair has been working well until the other day. When I started up my truck in the morning the service 4wd message popped up and stability control disabled as well. Also the seat heater was on. I turned it off and with in a few seconds the seat heater came back on. I drove to the gym which is a 10 mins and the seat heater came back on after turning it off 6 times. When I left the Gym it did the same thing but only a few times on the way to work which is about 45 mins. After work started the truck up and no issues. Has not came back since. Anyone seen this or heard of this? The day was around 65°F and humidity was around 75 so it was pretty sticky but I can not explain it.

 

[Jenzenauer]

Update: Error Code was C0327.
I am heading back to the dealership as the problem has returned. Sporadic Service 4wd issues and Stability Control Disabled. So apparent paying the Chevy Dealership was no better than working on it my self. Really sad to pay $900.00 to have a pro fix and it is not fixed. to be continued

 

[rzabel]

Update: Error Code was C0327.
I am heading back to the dealership as the problem has returned. Sporadic Service 4wd issues and Stability Control Disabled. So apparent paying the Chevy Dealership was no better than working on it my self. Really sad to pay $900.00 to have a pro fix and it is not fixed. to be continued

I've gone through 3 encoder motors, the last two installed by the local GM dealer. I just got the Service 4WD message again last week. I long for the days of a lever on the floor.

 

[TJ Baker]

Just a thought here. Last year I replaced the position sensor inside the encoder motor on my 05 Yukon. There was some degradation of the resistive material as well as some 'schmutz' on it that I suspect came from grease on the shaft but could also come from a leak from the seal on the transfer case? Mine has been fine since the replacement sensor went in but if I were seeing multiple failures I might be tempted to have a good look at the seal on the transfer case, or at least do a thorough inspection of the encoder position sensor of the failed unit.

 

[Jenzenauer]

Ok thank you for sharing. When I give up on the dealer I will look for this. I know when I changed the encoder motor the shaft/gear was pretty clean and not oily like in your picture. When i took the old one off I looked for this issue before replacing and did not notice a build up on the little fingers but who knows. I am headed back to the dealership as soon as the Service 4wd message come back on. Unfortunately it typically happens when I start it to go to work at 5:30am and the dealer is not open. lol
Apparently they can only read that there was an issue and not what the issue is unless the message is actively displayed or that is what they told me. He said they think it is a wire or wired connection but unless I want to pay for exploration that could take up to 5 hours I need to bring it back in with the message on and not turn it off so they can scan it. So TBD I guess.

 

[Jenzenauer]

Update so far. Since my visit to the Dealership I have not had a single Service 4wd message. WTF. Did they clear the codes maybe and it is going to work for 2-3 months again? I am so irritated with this issue.

 

[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.