Code 379-04?

2011 CHEVROLET SILVERADO
172,000 MILES • 4.0L • 4WD • AUTOMATIC
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RCBECKLEY88
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Getting this code along with the service 4wd. When shifting from 2h to auto it blinks and takes 20 seconds before switching. It goes to 4h and 4lo faster. I can hear encoder motor click but after watching scanner live data the front axle never engages. I replaced front actuator with gm oe part and didn’t help. Tested actuator at connector and it’s not getting power. Also not getting power at midway point near fuse box. Pulled harness from midway point to actuator and removed plastic covering and found no damaged wires and both connectors looked fine with no corrosion. Wondering if it’s a grounding problem or a damaged wire between the tccm and the mid point connector or just a failing tccm? New parts include tc encoder motor, front actuator and ignition switch. Checked and cleaned as many grounds as I could but I’m sure I’m missing a few. What grounds would be most relevant for my problem? Also when I watched scanner live date you could see that the command was given to go from 2h-auto-4h-4lo but it would never say engaged on front axle. Not sure where else to turn unless it’s replacing tccm.
May 23, 2026 at 3:30 AM
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STRAILER
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This is a good one, based on your testing, I’d be chasing an open power/control circuit between the TCCM/fuse block area and the midpoint connector, or a bad TCCM ground/connector terminal, before replacing the TCCM itself. I have seen the switch cause this problem as well. Here is a guide to help you check the wiring and the transfer case system wiring diagrams so you can see which fuses to check for power as well.

C0379-04 often points toward an open/high-resistance type fault. If the circuit is open, the TCCM may command engagement but never see current flow or axle feedback.

https://www.2carpros.com/articles/how-to-check-wiring/

I marked the grounds you need to check on the diagrams. Check out the images (below). Please upload an image or a short video in your response, so I can see what's going on.
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May 23, 2026 at 5:34 PM
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RCBECKLEY88
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Just to clarify I am also getting codes P2534 and PO700. I have checked and tested all related fuses and cleaned and reconnected grounds under drivers side door, radiator mounts on both sides and the ones in engine compartment and negative battery to front engine block. Must be something open between tccm and midway point at fuse box or tccm is faulty. This whole issue started after swapping out IPC for issues I was having with it. After installing new programmed cluster from ISS the problem I was having was still there plus service 4wd, service suspension and I think service trailer was all showing up. I took out and put back in original cluster and everything was fine besides service 4wd light still being on. I have owned the truck for 8 years and this was the first time the service 4wd light has been on.
May 23, 2026 at 7:21 PM
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RCBECKLEY88
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How can i safely test power at the tccm to see if it’s sending anything towards the midway point connection at fuse box?
May 23, 2026 at 7:57 PM
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RCBECKLEY88
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What are the actuator output wires at the tccm?
May 23, 2026 at 8:16 PM
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STRAILER
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So I would check the wiring to the front differential, I has another user find the wiring harness rubbed through there, there is a TSB on it. You can safely check for power using a test light, this guide will help you.


https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester/

With the system on, check the pink wire at eh front diff actuator and the red/blk wire at the transfer case actuator. Let me know what you find.
May 24, 2026 at 2:35 AM
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RCBECKLEY88
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The wiring from the midway connector to actuator looks good unless there is an internal break somewhere. Both connectors look good with no corrosion. I have tested the front actuator pink wire with system on and showed nothing. Also showing no voltage at midway connector. I looked at wiring diagram so I want to test if tccm is even sending power towards actuator when commanded or maybe a continuity test on the 3 wires from tccm to the midway connecter. I know you mentioned transfer case wires do I need to be checking them. What is the most important test I can do to determine if this is a tccm output issue or a broken wire-ground issue?
May 24, 2026 at 3:09 AM
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STRAILER
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You found the problem, if the pink wire does not have power with the truck on then please check the fuse "TRANS IG1" in the fuse panel under the hood. This fuse supplies power to the actuator.

P2534 — Ignition Switch Run/Start Position Circuit Low Voltage

and

P0700 — Transmission Control System Requested MIL

These can be caused by a bad ignition switch which will cause all of your problems but lets see if the TRANS IG1 fuse has power first.

https://www.2carpros.com/articles/how-to-check-a-car-fuse/

Let me know how it goes

May 24, 2026 at 3:13 PM
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RCBECKLEY88
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Strailer I appreciate the help because I am beyond frustrated at this point. So I checked the trans ign1 fuse and it was only lighting up on 1 side. I replaced with a brand new fuse and it did the same thing briefly lighting up on the side that did nothing with old fuse. I assume this means a shorted out damaged wire somewhere between the tccm and the actuator or maybe a bad ground somewhere? I know you mentioned ignition switch for the other codes but that is brand new. What is my next step?
May 24, 2026 at 5:18 PM