4WD service on and no indicator lights

[kybob]

Not sure where to post this as I’m not sure if it’s a drive problem or an electrical problem.
04 Yukon 135,000 mi , bought it in Oct. I used 4WD briefly when I got it, all seemed good. When we had a good snow here a couple weeks ago , I used my 99 Yukon.
( didn’t want the “ new one “ to get hit )
Anyway, I took the 04 to Gulf Shores ( approx 570 mi ) and all was good till the day we left to come home. The “ Service 4WD “ came on. I thought it was a schedule reminder so I hit the acknowledge button. It continued to come on periodically on the way home ( usually after getting gas and restarting ) I also noticed the red led on ( neutral light? )
I know it was in 2hi as my mileage was 16/17.
Went down today to see what was what , and after hitting 2 hi, 4 hi and Auto 4WD, now all the lights are out. But all 4 Amber and the red neutral lights come on when I turn the key to “ on “ , but when I start the truck, they all go out.
It feels like it’s in 2 hi, but I haven’t driven it.
Any thoughts are appreciated.
BoB

 

[Chubbs]

Are you going to troubleshoot this yourself or have a professional repair the truck? If you tried searching the web for a solution you will find various suggestions as to the parts responsible or that have failed. There are several different components to the system, any of which could be at fault. The proper approach to diagnosis would begin with application of a OBD diagnostic tool where the fault codes are extracted from the control module and systems tested if said tool has the capabilities.

without knowing the fault codes, 1 can only assume that either the mode pack or encoder ring is at fault here. The less likely responsible party would be the TCM, but not impossible. Let the board know of your intentions moving forward with repair.

try researching the switch failure via Google search and compare other's testimonials with your recent experiences regarding the issue. There is a video on YouTube by May03LT describing the process of testing the switch bank with a multimeter. You can try that or pick 1 off of a junker at a nearby recycler if you don't mind throwing parts at it. If you have access to another vehicle with same 4x4 system, remove known-good unit and test for proper function @ your vehicle. The switch bank just pops out with tabs, then an electrical connector.

 

[Fless]

I had similar issues at about 92K on my '04 Hoe's clock, not long after I bought it. I'd be driving along and the light on the dash switch would show "neutral", but I'm cruising along with power so I know it's not in neutral. Stop, turn off engine, restart, the light switches back to 2wd and everything is normal. Ended up being the encoder motor on the transfer case. Not really all that difficult to change out. Oh, and I did get the Service 4WD message intermittently. My T/C RPO code is NP8.

Not much later we noticed that in 4x4 there was no power to the front wheels, had an audible clunk when switching drive modes, and had to have the T/C rebuilt. FWIW, and not sure if true, I've have heard that a T/C on its way out can take out the encoder motor.

 

[kybob]

I’m going to order a new switch tomorrow. My OBD II is on loan and I won’t get it till Tues.
Another question, is there a fuse I can pull to disable the 4WD ( to keep it in the 2H )? I don’t want it to be trying to “ shift” on its own.
I looked for a “ transfer case “ fuse, but the only thing I found is a 15A fuse on the panel on the LH side of the dash. It’s marked “4WD”
If I pull this fuse , can I safely drive it ?
Thank you all.
And yes, if it’s not too involved I’d like to repair it myself. I do not have a lift though.


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[kybob]

Changed switch, no help. Checked and reground wires to frame , no help.
Pulled both fuses ( 15 amp in cab, and 30 amp under hood ) no help.
My scanner didn’t show anything.
As bad as I hate to , I guess it’s off the the stealership


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[jlp78]

I had this happen on my '05 Yukon. First symptom was the stability system disabled on the CID, then service 4wd. Then observed that the lights on the selector were ... weird. Sometimes all on, sometimes all off, sometimes showing some weird position. My OBDII scanner didn't show anything, but it apparently doesn't know how to query the TCU. I parked it, not wanting anything crazy to happen while driving, and found the battery dead the next morning.

It was the transfer case control motor. I found that the wiring harness was damaged and at least one wire was stripped and shorting out on the frame. Quite possibly the motor itself was fine, but I replaced it with a Dorman unit. When I took the old one off, I discovered that it was a remanufactured unit, so it had presumably failed before and been replaced.

Replacing it was easy in the driveway. Put the front end up on jacks and shinny under from the driver's side. You have to pull the front drive shaft (between the transfer case and front diff) to have room to get at the part in question. Took about two hours all in all (from starting to jack up the truck to letting it back down).

The youtube video I had been watching for instruction said to plug the new motor in and turn the ignition on, then select the same transfer case setting that you had last had the truck in (I had had it in 2HI) before positioning and bolting on the new unit. I assume the intention was to make sure everything lined up correctly, but I found that my TC was not in 2HI and I had to manually twist the gear on the TC until the transfer case control motor would slip into place. All in all, it went pretty smoothly.

 

[W8TVI]

I had something similar happen to me last winter when we had a really cold few days. It got to the point where it wouldn't shift out of 2HI. Finally, a couple of days later it got warmer and everything went back to normal, and it worked great the rest of the winter.