Service 4wd Message

Jenzenauer

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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

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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 The last two have been replaced by the dealer, but they never mentioned a "re-flash".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

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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.
 

Jenzenauer

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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

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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

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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

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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.

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Jenzenauer

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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

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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.
 

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