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2004 GMC Sierra 2500 trouble code help

rwe01

By rwe01
in Ask A GM Technician

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rwe01 New Member

rwe01

Posted
Posted

Need some help from those who know better than I. I have a 2004 GMC Sierra 2500 4wd that had the infamous "Service 4wd" come up. It resets itself at engine restart and does not display all the time. The following codes are displayed:

 

B0790 - Transfer Case Neutral Indicator Circuit

B2725 - Mode Switch Circuit

C0306 - Motor A/B Circuit

C0327 - Encoder Circuit

C0374 - General System Malfunction

U1084 - Unknown

U1301 - Unknown

 

Truck drives fine with no problems.

 

When "Service 4wd" comes on, the 4wd will not engage but turning off engine and restarting resets it. After restarting it will go in and out of 4wd. It does this about once every 4 weeks or so. I have read alot about moisture issues but wasnt sure with so many codes at the same time. Hopefully someone has seen this combination before and can provide some guidance so I dont waste time and money on symptoms and not the cause.

 

Thanks for looking.

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

the message means there are codes ,thats it ,

 

please refer to owners manual for info on meassages

 

clear codes and road test and operate 4wd and reply with CURRANT codes .....thats it

 

you have to many for any internet diagnoses

rwe01 New Member

rwe01

Posted
  • Author
Posted

I cleared the codes. Took the electrical connection loose on transfer case (had water in it) dried it out and applied dielectric grease and so far so good. Put in 4wd drive and checked codes again. None displayed. We'll see.

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