(another) Service 4wd

[SnowDrifter]

Had another one pop up. Managed to pull a code this time. Message went away after engine restart, works fine now. Bleh.

Anyone have a wiring diagram so I can check pinouts and verify it's the switch before I shotgun said switch?

 

[SnowDrifter]

Bump? Anyone?

I'll take a wiring diagram or any info for the cause behind these switch failures. I'm not opposed to rebuilding it myself on account of aftermarket parts being such a shit show. Dealer wants 170 for it. Local store wants 105. Amazon is like 20 bucks but I have some doubts about any amount of build quality / QC during manufacturing on those

 

[Doubeleive]

Bump? Anyone?

I'll take a wiring diagram or any info for the cause behind these switch failures. I'm not opposed to rebuilding it myself on account of aftermarket parts being such a shit show. Dealer wants 170 for it. Local store wants 105. Amazon is like 20 bucks but I have some doubts about any amount of build quality / QC during manufacturing on those

I would roll with a used oem one from the local scrap yard if they have any usually they are snatched up quick, lkq might have one, they have a circuit board inside not sure what goes wrong with them.

 

[Fless]

@SnowDrifter, two-speed transfer case with round Auto button at top of switch?

EDIT: https://www.tahoeyukonforum.com/threads/03-4x4-issues.112093/#post-1345015

 

[SnowDrifter]

@SnowDrifter, two-speed transfer case with round Auto button at top of switch?

EDIT: https://www.tahoeyukonforum.com/threads/03-4x4-issues.112093/#post-1345015

You, sir, are a saint!

 

[Fless]

The two I have for my '04 (I have a spare from U-Pull) are both apparently OE and have "TRW" molded into the backside. I've never tried others, as these have so far passed the resistance tests and I've replaced the backlights in both.

I'd be interested in if your switch fails the resistance test.

 

[Roger L]

I had 2 new ones from Napa work for a week, the last one passed resistance test, ordered one from an Oregon GM dealer and it says made in China on the back, it passed too, still no worky.

 

[Fless]

If you haven't checked and cleaned the two ground wires on the body behind the LF wheel, one of those is for the 4x4. Think it goes to the harness for the TC control module under the dash. I believe there is also a splice in that wire around (underneath) the brake booster; follow the ground wire up the firewall to see if that's a good connection.

A Tech 2, and maybe other scanners, will read the reference and return voltages to/from the encoder motor. I have no idea what the return voltages should be, but the reference is either 5v or 8v, depending on your system.

 

[SnowDrifter]

The two I have for my '04 (I have a spare from U-Pull) are both apparently OE and have "TRW" molded into the backside. I've never tried others, as these have so far passed the resistance tests and I've replaced the backlights in both.

I'd be interested in if your switch fails the resistance test.

If you haven't checked and cleaned the two ground wires on the body behind the LF wheel, one of those is for the 4x4. Think it goes to the harness for the TC control module under the dash. I believe there is also a splice in that wire around (underneath) the brake booster; follow the ground wire up the firewall to see if that's a good connection.

A Tech 2, and maybe other scanners, will read the reference and return voltages to/from the encoder motor. I have no idea what the return voltages should be, but the reference is either 5v or 8v, depending on your system.

Ref voltage for mine is 5v.

Switch tests out good, though I did note pin tension on B of C2 is lame. Seems to correspond with some flickering lighting on the thing when I go over bumpy roads. Not really confident that would be my fix though.

One of the pins (and I already forgot which one) had a bit of a patina on it. Probably from an interior water leak I had last year

Will clean up those grounds you mentioned, adjust pin tension, button her back up and see where that gets me. Given how intermittent the thing has been, and the switch testing good, I'm temped to believe at this point it's just a garbage connection somewhere *knock on wood*

 

[SnowDrifter]

Well she's all buttoned back up. Works now so at least I managed not to break anything! Though how intermittent this is it'll be a hot minute before I know of it worked or not. Will update this in the future

 

[Fless]

Hopefully then it was just a bad connection, and cycling them fixed it.

 

[SnowDrifter]

Problem not solved. Issue persists. Same code

However, I did get an interesting visual here as I wslas driving at night. The back lights for the selection buttons did not work(though the amber selection indicator did) . But they did after an ignition cycle and the issue resolved.

Grrrr. Need to dig deeper (****)

 

[SnowDrifter]

Ooookay so combining the lack of back light with throwing the code, and knowing the conditions for the code, I'm left with one of a couple options (I think, someone correct me if I'm wrong please help this is a cry for help)

1. There's an issue with supply voltage to the switch. I don't believe it to be ground related as ground for the switch, based on my understanding of how it's wired, wouldn't affect the output signal which is the condition for setting the code. This bit I'd need some knowledgeable folks who know where the power supply comes from, where the wire runs, and any pinch points

2. A fault in the power supply feed internal to the switch itself.

Both of these are difficult to test being that I can't seem to replicate the issue on a consistent basis. So this would be a case of inspecting what I can and seeing if there's anything obvious, or wait until it gets worse and I can replicate the problem to appropriately determine the fix

Any input /help here would be appreciated. This one's kicking my ass

 

[Fless]

I won't be much help on this as I've not done any related troubleshooting and have never had that code, but I'd be inclined to throw a UPull or cheap switch at it (after testing it) to see what happens. From what I've read it's the switch a high percentage of the time. I'm not sure if the Tech 2 will read the ignition voltage, but I do know it will read the 5v from the ATCM under the dash.

I'm not good at reading wiring diagrams but it looks like the ignition voltage doesn't come from the ATCM. You probably knew that already.

Might also be a good idea to pull the ATCM out and clean the two connectors. Kind of a pain to get it out from under the dash, though.

 

[Fless]

Thought of another thing to try.

If you think the switch might be the cause, you could disassemble it partway and clean the contacts, and touch up the solder joints on the two connectors. Sorry these pics aren’t the clearest.


Here’s the switch with the cover removed:

Pull off the clear light diffuser straight up and set it aside:

Pull (peel) off the rubber switch contact piece, and clean both those contacts and the corresponding ones on the circuit board with electronic contact cleaner or alcohol. I like to use something that will not only clean the contacts but leave a little film of protection to keep them from oxidizing:

When you reinstall the rubber piece, make sure the little rubber nibs* seat all the way in the two holes on either side of each contact. The rubber edge should be flat to the circuit board and not lumpy anywhere.


It would be a good time to re-flow the solder on the contact pins. (If you were to be replacing the backlighting, the correct way to do that is to desolder all those pins, since they’re what hold the PC board to the switch body and contact pins.)


* I wanted to say “teats” instead of “nibs” but I know how the prudes on this forum would react to that. LOL