07 Yukon C0306 Service 4wd (most fixes tried already)

[89Suburban]

Guess it's time to get the test light out. Anyone have wiring diagrams for this system?

Look at D-11. Hopefully this helps.

2007_LD_ElectricalPickupsChassisCabs.pdf

drive.google.com

 

[Tray0625]

I will check it out, just need a full day i can dig into it. Much appreciated. I have skimmed this diagram a few times in the past. Having trouble making sense of what wires are which pins in connectors, and how it translates to what I'm looking at. Will do more studying.

I was trying to install a new stereo this weekend and found more "clues"

Under the driver's dash panel there are 4 cut wires dangling (previous owner). One of them is light blue 18ga is the only one that has power running to it. Others do not. These are directly next to the TCCM that I replaced. Since i moved (just moved, not unplugged) the TCCM to try and follow these mystery wires I have a new "transfer case control module" light on.

I'm suspicious. Perhaps pins are loose in TCCM harnesses? Or a wire is poorly spliced?

I'm assuming previous owner had an aftermarket alarm, breathalyzer, or GPS tracker in the truck and did a poor job of removing it.

Also, when opening driver's door, the dome lights do not come on as they do for all the other doors. Door functions fine otherwise. Been like that since I bought it, just assumed it had a bad door latch. Maybe that's where the light blue wire is supposed to go?

I'm now wondering if they cut a wire to the 4wd, or reconnected something incorrectly.

Oh, and the stereo gave static feedback constantly. So I pulled it back out. Not sure if that problem is connected to the others I just listed.

So. FML.

What's the little blue wire go to? What about the others? Why the new TC light?

Is there a place to get wire assignments/pin connectors?

What would your next move be? Lost cause?

 

[Tray0625]

I will check it out, just need a full day i can dig into it. Much appreciated. I have skimmed this diagram a few times in the past. Having trouble making sense of what wires are which pins in connectors, and how it translates to what I'm looking at. Will do more studying.

I was trying to install a new stereo this weekend and found more "clues"

Under the driver's dash panel there are 4 cut wires dangling (previous owner). One of them is light blue 18ga is the only one that has power running to it. Others do not. These are directly next to the TCCM that I replaced. Since i moved (just moved, not unplugged) the TCCM to try and follow these mystery wires I have a new "transfer case control module" light on.

I'm suspicious. Perhaps pins are loose in TCCM harnesses? Or a wire is poorly spliced?

I'm assuming previous owner had an aftermarket alarm, breathalyzer, or GPS tracker in the truck and did a poor job of removing it.

Also, when opening driver's door, the dome lights do not come on as they do for all the other doors. Door functions fine otherwise. Been like that since I bought it, just assumed it had a bad door latch. Maybe that's where the light blue wire is supposed to go?

I'm now wondering if they cut a wire to the 4wd, or reconnected something incorrectly.

Oh, and the stereo gave static feedback constantly. So I pulled it back out. Not sure if that problem is connected to the others I just listed.

So. FML.

What's the little blue wire go to? What about the others? Why the new TC light?

Is there a place to get wire assignments/pin connectors?

What would your next move be? Lost cause?

UPDATE;

Some problems solved, and some new clues...

* I'm thinking the light blue wire is driver's door light, will test and confirm

* Feedback from new stereo is most likely due to the Kenwood HU over powering Bose amp, so I will bypass the Bose amp for the door speakers only. That should fix that issue.

* AS FOR the 4WD (which is what this post was about in the first place) We've had a crazy cold winter and I have not had time to get back at it yet. We got a bunch of snow, and I found a new clue; The 4WD works perfectly fine AS LONG AS THE "SERVICE 4WD" light is not lit. When the service light comes on, it will not shift and is stuck in whatever setting. Usually when you first start the truck after its been sitting a while, you have a minute or two before the "Service 4WD" light comes on, and you can select what ever setting you want. During longer drives the "Service 4WD" light will cycle on and off a few times. So it's intermittent.

I am assuming a wire issue, OR a lose pin in a connector somewhere. Intermittent may make it difficult to test with a signal scanner, but that's what I plan to do next.

I pulled and cleaned connectors on TCCM, encoder, and actuator. I was conscious of plugging them in deliberately & solid. I also pulled and cleaned the other smaller connectors near the encoder motor, and I did notice that one of those connectors coming from the main harness is taught with zero slack to plug into its sensor. I am not sure what sensor it is. But it did concern me that it was so tight. I am suspicious if that's my culprit. Need to find out if those wires are just pwr/gnd and can be extended, or if they're info wires I suppose.

I did have an issue with the drivers window not rolling up, and found the wires that go into the connector liked to be folded a certain way. When folded to the left, no power. When folded to the right, works fine. So I'm thinking it's something silly like that.

Anyone have any other suggestions on how to find a finnicky gremlin like that, other than signal scanner?

Thanks!