GMT800: "SERVICE 4WD" message, unreponsive 2WD button

[thunderstruck]

Hey guys, I'm hoping someone here can shed some light on my 4WD issue. The other day while I was leaving my farm, I put my Avalanche into 4HI to make it sure it was still working. It engaged 4HI without a problem, but near the end of the driveway I got a "SERVICE 4WD" message on the DIC. I tried putting the truck back into 2WD before getting back on the main road, but the button was completely unresponsive. It wouldn't blink like it was trying to engage or anything, it just did nothing. So I drove about three miles in 4HI before I tried the button again, and then it went right back into 2WD.

The next day I got the SERVICE 4WD message while just driving around normally in 2WD. I pulled down a dirt road and had the same issue, it engaged 4WD easily but I had to repeatedly press the 2WD button to get it to respond.

Same thing today, but I tried it in my driveway with the engine off. When I tried to re-engage 2WD, I couldn't hear the actuator at all, until the button finally responded and it went right back into 2WD.

I would guess that it's simply my 4WD switch that is defective, but I just want to be sure. Anybody had a similar issue?

 

[PenguinLTZ]

Switch, yep.

 

[Matt_]

The two most common failures are the switch and the encoder motor sensor.

The switch is easy to replace (about 10 minutes) and only about $60 so id start there.

The encoder motor sensor is $70-$80 in parts (sensor + gasket) and isn't "hard" to replace... just takes a bit more time and patience.

 

[Bigredmariner]

Encoder motor sensor, I wouldn't waste the money on the switch. The switch used to be the problem in the earlier models but by 2003 and on the cold solder problem had been fixed.

http://www.truckmodcentral.com/forums/showthread.php?p=449595

http://www.truckmodcentral.com/forums/showthread.php?t=2290
http://truckmodcentral.com/forums/[...iner/2011 Silverado/Dropfinished011.jpg[/IMG]

 

[PenguinLTZ]

I thought the message coming on while just driving around in 2wd was the give-away for the switch?

 

[Bigredmariner]

No, the message will come on in both circumstances.

 

[PenguinLTZ]

A'ight My bad

 

[Bigredmariner]

A'ight My bad

No problem, both times that I have had the problem the sensor has been the issue. The switch doesn't seem to be a problem on the newer models, but either way the message will come up with any malfunction of the system. Which can also include the Transfer Case Control Module.

 

[Matt_]

No, the message will come on in both circumstances.

And if you get the code read, it probably is C0327 which is something like "encoder motor sensor fault"

 

[Bigredmariner]

No, the message will come on in both circumstances.

And if you get the code read, it probably is C0327 which is something like "encoder motor sensor fault"

Correct, but the code will not be able to be read by most hand held scanners, like the ones NAPA or Auto Zone have. It will take a Tech 2 or similar scanner to read that deep.

Not to worry though, once the problem is fixed it won't show up to you any more on the dash.