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2004.5 GMC Sierra 2500hd SLT Crew cab 4x4
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Hello everyone. I'm only mechanically inclined enough to get myself in trouble. But here I am. A year into a "all it needs is a" project 04.5 Sierra SLT. I've replaced what needed replacing and then some. Truck is near done. Just a couple bugs. I've searched high and low on the c0379 code. But none matched my exact happenings.


Obviously. Dic says service 4wd. When you press a button to put it in 4wd or 2wd. THE TRUCK Stalls but it does go into whatever you select.... If you press a button giving it a little fuel. It sputters but does not stall...and goes into whatever selected

So what does one make of that. I am gonna have a look at the ground. But judging from what I read. Nobodies engine has shut down

Now back when I put the engine in. And was checking codes. Getting the engine figured out. There was an encoder ring code.... I ignored it as the engine was the focus.... That code is gone. Just the C0379.

TIA and sorry in advance. I ramble too much. My wife beats me for it,and it makes me ramble even more
 

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I think you have a short to ground. In any case, wiring, connector, or replace the module




C0379 Help!



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C0379 Help!
Postby Willfrommaine [OP] » Feb 01 2017, 3:38am

So I've replaced the front actuator, encoder motor, and switch. Still getting a C0379 code... I've pulled the TREC and 4wd fuses and they are not blown. I've sanded down the ground on the frame and even cut off and replaced the connectors. Still getting the same code.

I have not replaced the TCCM and have not done a software update via the dealer. Anyone have any other tips?

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Re: C0379 Help!
Postby Chevboy0167 » Feb 01 2017, 7:19am

Check for continuity in all the wires in the wire harness that go to the front actuator. Trace the harness from actuator plug up to a plug or termination point in the engine bay. Just to confirm the wiring is intact. I believe there was a TSB to replace harness along with replacing the actuator?? Not to sure on that one tho. Also, you should get to a dealer to make sure you have the most updated flash software. Has to do with temps below 30* that I have read in other forums. Just some thoughts.

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Re: C0379 Help!
Postby GMT604 » Feb 01 2017, 8:15am

C0379 is all about the axle actuator control circuit. Should be 12V on the brown wire at the actuator, and the TCCM should see 12V coming through the actuator on the light blue wire. When the TCCM grounds the light blue wire the actuator locks the axle. If either circuit is open, grounded, or shorted to voltage you will get that code.

Fast test: Key ON engine OFF and 2WD selected use a meter from battery ground to test for 12V at the brown wire, then the light blue wire. Should be 12V at both. Selecting 4WD, the light blue wire should have no voltage.

Inspect the harness and connector for corrosion or spread pins, tug on each wire at the actuator connector to see if one is broken.


C0379 - Front Axle System Malfunction
 
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