Problem Description and Possible Solution
The 4WD transfer case encoder motor position sensor or the selector switch may fail causing the service 4WD message to be displayed. Fault code(s) stored in the transfer case control module will be of assistance in determining the exact fault causing the message to be displayed.
Average mileage: 111,750 (70,000–150,000)
Drive Train affected: 4WD
16 people reported this problem
automatically switches from 2hi to auto4 to 4hi etc. turn car off, restart, reposition sensor button to 2hi
have replaced parts front axle 2times transfer case encoder buttons transfer was out and checked out by a award winning GM tec at dealer . No codes front end locks in encoder goes in In 2wheel front drive shaft turns easy. In auto vary little pressure cane turn it In 4 wheel the drive shaft can still be turned . This has been going on now for years . Encoders modulators buttons even the transfer. Case apart more then I can remember I have checked fuses replaced every control part for the 4 x 4 I anyone can tell me what to do ?? please it's not any part replacement