Stuck In 4WD

[RoadTrip]

After snowmeggeddon up here in the central midwest, the roads got to where I could finally turn off 4wd on my ‘15 Yukon 2-speed transfer case. I switched from 4wd to 2wd while backing up into my driveway. I did not look to see if it completed the change before I shut off the engine. The temps here are double-digit minus at night and minus to single digits high during the day.

The next morning when I started it up I was greeted bu the message “Service 4wd System.” The transfer switch would still light up in 4wd, but not in any other position.

I pulled into the garage and checked the fuse: Good. I disconnected the battery for 1/2 hour until the fuse pins in the engine fuse box read 0.25v. I put a heat gun on several locations of the transfer case to see if the actuator motor had frozen. No change.

I connected my scanner and there are no codes stored. No CEL either, just the DIC message.

When these vehicles were new, there was a recall for bad 4wd modules (under the driver’s kneepad). The PO of mine got that service call done.

What is the best way of telling if it is the module or the motor that’s bad? They’re both about $350 and I’d rather get it right the first time.

 

[Fless]

Does your code reader read body and chassis codes? It needs to in order to read the 4wd codes.

 

[RoadTrip]

I believe it has engine and transmission options, but I didn’t see body codes.

I talked to a local shop that said they will diagnose it Saturday.

 

[LegalBrief]

Vehicle won’t go into 4H properly while backing up. Only can switch from 2H to Auto while going forward. All other switches should be from neutral while fully stopped. @RoadTrip i think u busted something

 

[RoadTrip]

Vehicle won’t go into 4H properly while backing up. Only can switch from 2H to Auto while going forward. All other switches should be from neutral while fully stopped. @RoadTrip i think u busted something

I miss my transfer case floor shift on my OBS: By the feel alone, you knew if the T-case didn’t like it.

Thinking back, I’ve never engaged or disengaged 4wd in reverse in any vehicle, but with the electronic control I didn’t think twice because I thought the drivetrain would sync and finish the change when everything was lined up.

Anyone else had 4wd switching problems?

 

[RoadTrip]

The shop checked it out today and verified the problem is nothing mechanical and not the fuse.

I cleaned the ground under the driver’s feet to be extra sure.

So apparently I need to reset my 4wd module or replace which traditionally means going to the stealer.

Can I buy a reasonably priced scanner that will let me reset the module myself, or can I just buy a new module without have to flash it to my VIN?

TIA

 

[RoadTrip]

Still hearing the echo of my last question…Bueller…?

I found a GM TSB that said ‘15 models that engage 4wd below zero (as if has been for weeks in MN) may get the transfer case actuator stuck. The part number they told shops to use as a replacement is different than the original part number. It is a different construction, not a part number swap. It was covered under the factory warranty, but if you hadn’t operated your rig in 4wd in sub-zero temps in the first 24k, well sucker, you’re SOL.

Took my Yukon to another shop today that had the capability to reflash my 4wd module. The module was fine. It really was the actuator that was stuck.

And now I get stuck paying for the part and labor.

 

[Doubeleive]

for future reference, the actuator just unscrews to check and verify if it is stuck, easily replaced if so.
does not require programming
the encoder motor is the more common failure and can also be replaced, does not require programming. but does use a relearn procedure anyone can do

 

[RoadTrip]

for future reference, the actuator just unscrews to check and verify if it is stuck, easily replaced if so.
does not require programming
the encoder motor is the more common failure and can also be replaced, does not require programming. but does use a relearn procedure anyone can do

Thank you for this information. I like the TRQ videos that you suggested -- easy to see and no nonsense. I bookmarked TRQ for future reference.

I didn't know the encoder motor was a common failure point. Had I known it did not require programming, I would have replaced the motor myself.

 

[Doubeleive]

Thank you for this information. I like the TRQ videos that you suggested -- easy to see and no nonsense. I bookmarked TRQ for future reference.

I didn't know the encoder motor was a common failure point. Had I known it did not require programming, I would have replaced the motor myself.

I like there video's there TRQ and 1A brand products though are only a touch above detroit axle, I would only use there parts if you fixing something to sell they do not hold up.