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Service 4WD Light on in the 05...

Ed HD

Formerly: Dad's 05 LLY
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So tonight I had to pull the truck further in the shop to get my car in, and Service 4WD comes up on the DIC, and the yellow indicator light comes on on the 4WD button is flashing, and the 2WD button light is on.

Dad said the other day he was pulling out of a spot, had switched it from 4WD to 2WD, and he changed it from R to D, and he heard a clunking, and summed it up to dis-engaging.

I'm afraid this has something to do with the pump rubbing. I'm gonna put it on the lift this weekend and see what's wrong, and it's going to the dealer next week to get Tech II'd, and an estimate. Anyone had this issue that can lead me in the right direction?
 

Ed HD

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Scanned it at work today, and it had a C0379 - Front Axle Circuit Malfunction code. The identifix solutions were to replace the axle solenoid or the Transfer Case Module. It's currently intermittent, so I'm going to check and clean the connections at the axle. Hopefully that fixes the problem.
 

BoostN

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When I would get the Service 4WD light(previous trucks) it was always the push button unit bad itself. Replace it and all was well.
 

mmcna

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Would a half ton burb have the same issue.

I have no lights on the pushbuttons and service 4WD is on the dic.
Sometimes when it is first started you can push the buttons and hear the t-case working. My cheapo code scanner shows no codes

Any thoughts??
 

Franko914

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I just recently filed a complaint with the Office for Defects Investigation (ODI) for my 06 Avalanche's transfer case shifting into neutral from 2WD-Hi while doing 55 mph in top gear/OD. After coasting to a stop, I had to turn off the engine, turn it back on, switch to 4WD-Hi (to clunk-engage the t-case), then to 2WD-Hi to get going again... only to have the t-case shift into neutral, again, half a mile down the highway... repeated 2X.

Two days prior to this incident, I was driving along a 30 mph street and noticed the t-case was in 4WD-Hi (curious because I know I didn't switch it to that), so I slowed down to about 10 mph and pressed the button to switch it back into 2WD-Hi, got going again.

Back in Nov'09 while driving along the highway at 50 mph in 2WD-Hi, I, literally, observed the 4WD-Hi lamp start blinking so I slowed down to about 30 mph, then painfully "felt" the t-case switch into 4WD (2WD-Hi lamp went out, 4WD-Hi lamp went solid). I stopped at the shoulder and was able to switch back into 2WD-Hi with a clunk.

Did a tonne of research and narrowed it down to the t-case motor encoder ($$$), t-case motor encoder sensor ($65 RockAuto & GM p/n 88962315 ), and the dashmount t-case pushbutton mode-select switch ($65 RockAuto & GM p/n 15136039 ). Ordered both but never got around to installing them.

Going back to the most recent incident, I had the push-button t-case mode select switch on the dashboard replaced and the t-case hasn't shifted into neutral or 4WD-Hi again ever since (crossing fingers).

Some notes:

-- You must wait at least 10 seconds before switching modes on the t-case or else the computer locks out subsequent push-button commands to protect the t-case, sometimes for as long as three (3) minutes.

-- In some cases, the computer will revert to the last known mode successfully shifted into (which may have been the case when we were troubleshooting the recent incident -- i.e., reverted to neutral).

-- Shifting the t-case into AND out of neutral must be done with the vehicle stopped.

-- Shifting the transmission before the t-case shifting is completed can damage the t-case.

Hope the above helps.

Regards,
Franko
 
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mmcna

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I changed the selector switch in the dash and cleaned the grounds along the drivers side frame rail. The Service 4WD light is still coming on. How hard is it to change the t-case encoder sensor or the motor. It seems to be happening more often now.

Thankfully, when driving it is just showing it is in the neutral position.
 

RI Chevy Silveradoman

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I realize this is an old thread, but...
I noticed my 2006 2500HD Duramax not shifting into 4wd. I checked, had the C0379 code. Front Axle Circuit Malfunction.
I changed the front Axle Actuator. Did not fix the issue. I checked the ground under driver seat on frame. In tact, but I ran separate wire up to front of truck at known good ground spot. Still not shifting into 4wd. Without throwing parts at it, what should I check next? Is there a fuse?
Replace dash push button switch? Lights light up.
Replace encoder motor on Transfer Case?
 

BIGR

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Fortantly the only 4 wheel drive issue I have had on my 2006, 2500HD has been the actuator that's mounted in the center. It was leaking fluid when it was new. Dealer replaced it under warranty.

I have talked to the guys at my local garage where I have work done on my trucks. They said they have worked on more than one, full sized Chevy truck as far as the 4 wheel drive systems. Mainly has been installing new or rebuilt transfer cases.

However my daily driver 2002 S-10 has had about everything but the kitchen sink installed new on it. What it was doing when driving down the road it would at times when pulling a hill, it would start making one hellacious screeching noise in the front end. It was like the truck was trying to partially go into 4 wheel drive. I knew it was related to the 4 wheel drive system because if I pressed the 4 high button while driving down the road, 4 wheel drive engaged and the noise stopped. Also at times when I pressed the 4 hi button it would briefly light up and then go back to 2 wheel drive. At times it would go into 4 high and would not go back to 2 wheel drive. Auto repair place that I frequent put a new module or controller and switch on it. We tried that and still had issues. We were just trying the cheaper parts first to see if that would cure it. Deep down I figured the transfer case was the culprit. They replaced the motor on the transfer case and the motor went bad, a couple of times. Of course I only had to pay for one transfer case motor. It finally boiled down to the transfer case being bad. They found a used or rebuilt transfer case at a decent price and installed it. So far my 4x4 system has worked as it should, since it has a new switch, module, motor and the transfer case.

@RI Chevy Silveradoman, I wish you luck on it, hope it's not an expensive repair and something simple.
 

RI Chevy Silveradoman

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Thank you sir. I replaced front actuator. Still same issue. Tried to do the ground work around. Same issue. I guess Ill try replacing switch next.
Ill get it eventually. Lol
I'll report back when I do...
 

Will L.

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Idk issues of GM going through it. Fords have a tcase issue.
I would put it up on 4 HD jack stands and try cycling in and out of 4wd to see if that frees anything up. Seen it work on some jeep setups a few years back.

You can always drop front driveshaft to verify if tcase or axle...
 

THEFERMANATOR

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I realize this is an old thread, but...
I noticed my 2006 2500HD Duramax not shifting into 4wd. I checked, had the C0379 code. Front Axle Circuit Malfunction.
I changed the front Axle Actuator. Did not fix the issue. I checked the ground under driver seat on frame. In tact, but I ran separate wire up to front of truck at known good ground spot. Still not shifting into 4wd. Without throwing parts at it, what should I check next? Is there a fuse?
Replace dash push button switch? Lights light up.
Replace encoder motor on Transfer Case?
Here's the GM diag chart for that code.
 

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RI Chevy Silveradoman

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So...
I replaced front axle actuator. No go.
I cut the grounds under drivers seat and ran a ground to known good ground and wire nutted together. No go.
What next? Replace dash switch?
I was still getting the front axle actuator code
 

THEFERMANATOR

FRANKENBURBAN
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So...
I replaced front axle actuator. No go.
I cut the grounds under drivers seat and ran a ground to known good ground and wire nutted together. No go.
What next? Replace dash switch?
I was still getting the front axle actuator code
The dash switch has no connection at all to this code. You need a scanner to connect to the tccm so you can do the flow chart I posted.
 
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