4WD selector switch lights are not on and I cannot switch into 4HI, 4LO, or auto 4WD

Tiny
MAUNUNO
  • MEMBER
  • 2004 CHEVROLET TAHOE
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 135,000 MILES
Backstory:
Service 4WD message has showed up on dash intermittently since I bought it on 1/31/2020. On March 13th I went out for joyride and put the car in 4HI on dry pavement (bonehead move). I eventually turned it off after driving like that for 15 minutes and everything was fine. Come March 21st, I am driving home on the highway and notice that even though I am in 2WD, the neutral light on the selector switch is lit up. I get home 15 minutes later, turn off my car and turn it back on again. As I turn the car on, all the 4WD selector switch lights illuminate at once, but after 3 seconds they all turn off. This happens all the time now and I cannot switch into 4WD. Now when I drive the 4WD selector switch lights are not on and I cannot switch into 4HI, 4LO, or auto 4WD.

Things I have done:

Checked fuses
-TREC fuse has continuity
-4WD fuse has continuity
-IGN 0 fuse has continuity

Checked selector switch resistances
-Resistances were stable and within specs shown below
-No buttons pushed: 8.63-9.54 K Ohms
-Auto 4WD: 61.7-68.1 Ohms
-2 HI: 1.50-1.53 K Ohms
-4 HI: 656-670 Ohms
-4 LO: 2.32-2.37 K ohms
-Neutral (2Hi/4Lo): 1.015-1.035 K Ohms

Switched out TCCM with Dorman part
-Selector switch lights blinked when the car was started but no selector switch lights stayed on after the car was running, just as they have been. I returned this part and have the original TCCM installed now.

Does anybody have any idea what might be the problem? Also, does anybody have the TCCM colored wiring diagram? I'd like to see what wires are connected to what regarding the TCCM, selector switch, transfer case motor/encoder, and front axis motor.

Thanks in advance!
Sunday, April 12th, 2020 AT 10:10 PM

5 Replies

Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello, I'm Danny.

For some reason that design front differential/axle has a tendency to have issues with the actuator motor. Must be a design flaw. I've attached picture steps below on how to replace. I've also attached the transfer case wiring diagram below as well.I cut the picture into 3 pieces to view larger. Hope this helps and thanks for using 2CarPros.
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Sunday, April 12th, 2020 AT 10:37 PM
Tiny
MAUNUNO
  • MEMBER
  • 3 POSTS
Thank you for your reply and wiring diagrams! Do you think the front axle motor is causing the selector switch lights not to be on anymore?
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Sunday, April 12th, 2020 AT 11:06 PM
Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello again.

Do you happen to notice if the front differential engage/disengage?
Let me know and we'll go from there. Thanks again for using 2CarPros

Danny-
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Monday, April 13th, 2020 AT 12:04 AM
Tiny
MAUNUNO
  • MEMBER
  • 3 POSTS
I checked today and when I press anything on the selector switch nothing happens. All the lights are not lit up on the selector switch. Is there a way to test if the front actuator works by using a DMM?
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Monday, April 13th, 2020 AT 8:30 PM
Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello again.

I can find that out for you. Do you have access to a Power Probe? If not use a 12v power lead and ground to energize. I'll get back to you.

Danny-
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Tuesday, April 14th, 2020 AT 11:19 PM

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