The transfer case not shifting and the Service 4WD staying on?

Tiny
CHUNTIESGARAGE
  • MEMBER
  • 2015 GMC YUKON
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 140,000 MILES
I'm having issues with my transfer case not shifting and the Service 4wd staying on. I've already swapped out the transfer case motor, and the position sensor. I'm going to try swapping out the TCCM next. I checked all the wires on those connectors as well. I followed the wires all the way back up to the junction box. When inspecting the connector directly from the bottom of the junction box to the white connector with the grey lock handle and red lock button, I noticed things happening with other electrical components. I can't seem to find a part number for the connector and harness anywhere. No answer from the dealership on a part number either.
Wednesday, April 2nd, 2025 AT 4:07 PM

6 Replies

Tiny
CHUNTIESGARAGE
  • MEMBER
  • 4 POSTS
These are the photos of the connector.
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Wednesday, April 2nd, 2025 AT 4:13 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,622 POSTS
That is a bulkhead connector, and you say there is something wrong with it? Do you see corrosion? I am not sure what you mean with the problem with the connector, also, I would do a CAN scan to see if the TCCM is working before replacing it. Did you check the 4WD fuses? Here is how to do the CAN scan:

https://youtu.be/u-4syLc-ifQ

Please go over this guide and get back to us.
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Thursday, April 3rd, 2025 AT 9:45 AM
Tiny
CHUNTIESGARAGE
  • MEMBER
  • 4 POSTS
What got me to believe it could be the connector is it will randomly have different electrical issues, parking brake assist, trailer brake assist, stabilitrak, etc. The fuse block has been replaced in the past. So, when I was doing a wiggle test on all the wires from the transfer case and I got to the connector, different electrical issues popped on the dash. And looking at the wires from the connector they look crushed up but no corrosion. When I pulled codes with top don scanner, and I keep getting faults in the transfer. So, I'm left thinking it either the TCCM or the bulkhead connector. Do you happen to know the part number for the connector? Also, yes, I did check the 4wd fuses and swapped it out as well.
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Friday, April 4th, 2025 AT 6:55 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,622 POSTS
If the connector is crushed it will need to be replaced, you will need to call the dealer for this. We don't have a listing for it. Let me know if that fixes it.
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Friday, April 4th, 2025 AT 10:43 AM
Tiny
CHUNTIESGARAGE
  • MEMBER
  • 4 POSTS
I tried talking with a couple dealerships and they can't find it. Thanks for the help.
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Friday, April 4th, 2025 AT 11:20 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,622 POSTS
Can you just repair the connector? It might be part of the wiring harness. Can you upload an image of the damaged part so I can see it?
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Saturday, April 5th, 2025 AT 10:34 AM

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