Transfer Case Help

Laurence Broderick · September 27, 2019

I need help diagnosing a transfer case issue. I have a 2001 GMC Yukon Xl 5.3l that is stuck in 4x4 hi and it wont shift out of 4hi. When I attempt to shift out of 4hi it flashes what ever position I select and then it fails and returns back to 4hi. After a few attempts, an “Aux” fuse under the hood blew. I replaced the encoder motor on the transfer case as I suspected that was the issue. I continued to blow the fuse and not get any shifting. I got a 2^nd replacement encoder motor incase the first one was bad. I still had the same issue. I decided to replace the selector switches on the dash as they have been a known problem for this model. This did not fix the issue. I then replaced the Transfer Case Control Module with a used known good one. The issue continued. Each time I would try a new repair I would disconnect the battery and allow the truck to reset. I would attempt to shift the transfer case and it would try to shift and then go back to 4hi or it would blow the “Aux” fuse. This is where I am at with the truck. What is next? Should I replace the front axle actuator? Could I test if it’s the actuator by disconnecting the actuator and seeing what it does? Is there anything else I can try? I need the truck working for the winter!

swathdiver · September 27, 2019

26 minutes ago, Laurence Broderick said:

I need help diagnosing a transfer case issue. I have a 2001 GMC Yukon Xl 5.3l that is stuck in 4x4 hi and it wont shift out of 4hi. When I attempt to shift out of 4hi it flashes what ever position I select and then it fails and returns back to 4hi. After a few attempts, an “Aux” fuse under the hood blew. I replaced the encoder motor on the transfer case as I suspected that was the issue. I continued to blow the fuse and not get any shifting. I got a 2^nd replacement encoder motor incase the first one was bad. I still had the same issue. I decided to replace the selector switches on the dash as they have been a known problem for this model. This did not fix the issue. I then replaced the Transfer Case Control Module with a used known good one. The issue continued. Each time I would try a new repair I would disconnect the battery and allow the truck to reset. I would attempt to shift the transfer case and it would try to shift and then go back to 4hi or it would blow the “Aux” fuse. This is where I am at with the truck. What is next? Should I replace the front axle actuator? Could I test if it’s the actuator by disconnecting the actuator and seeing what it does? Is there anything else I can try? I need the truck working for the winter!

You need to know the code(s) so you can stop throwing money at this problem and solve it right. If memory serves, whenever an encoder motor is replaced, a relearn has to be done. You need to hold of a Tech-2 or other bi-directional scan tool that can read your transfer case and axle codes. Maybe the shift fork in the axle tube is stuck? Check the codes then you'll know what to fix.

You in Florida by chance? I've got a Tech-2.

Laurence Broderick · September 27, 2019

IN in NY and i cant find anyone who has a scanner. I can manually shift the transfer case with a wrench so I dont think anything is stuck in the transfer case. It continues to blow fuses even when the encoder motor is not on the transfer case. The #1 transmission shop in the area said he will take a look at it but he is a few weeks out right now. he recommended unplugging the front axle actuator and seeing if that fixes it. I dont mind making educated guesses and seeing if it fixes the problem. After the front axle actuator, there isnt much left to replace.

swathdiver · September 28, 2019

15 hours ago, Laurence Broderick said:

IN in NY and i cant find anyone who has a scanner. I can manually shift the transfer case with a wrench so I dont think anything is stuck in the transfer case. It continues to blow fuses even when the encoder motor is not on the transfer case. The #1 transmission shop in the area said he will take a look at it but he is a few weeks out right now. he recommended unplugging the front axle actuator and seeing if that fixes it. I dont mind making educated guesses and seeing if it fixes the problem. After the front axle actuator, there isnt much left to replace.

I would check all the wiring and look for a short, a bare wire grounding on metal maybe and of course related to that fuse. One of the various actuators could be internally shorted too but less likely I think. If you get a subscription to AllDataDIY, you can access the shop manual and wiring diagrams. Amazon sells some Bluetooth OBDII adapters that can read drivetrain codes which interacts with an app you can download for your phone to view the data. I'm not up to date on the latest and greatest though.