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.Google+
Car Problem Reports
Chevrolet Avalanche 2500 4WD Transfer Case Position Sensor/Selector Switch May Fail
Chevrolet Avalanche 2500 Problem
Drive Train Affected: 4WD
Average Mileage: 130,857 mi (95,000 mi - 180,000 mi)
Visitor, 2004 Chevrolet Avalanche 2500, 4WD, 95,000 mi
Repeated "service 4wd" light comes on. Unable to change transfer position. Dealer replaces sensor
My 2002 Avalanche will not switch into 4wd! I bought it new and take great care of it! Is there a recall on this issue?
Visitor, 2005 Chevrolet Avalanche 2500, 4WD, 108,000 mi
4WD message came on and will not engage into 4WD>
Visitor, 2002 Chevrolet Avalanche 2500, 4WD, 140,000 mi
Was raining hard and started up my truck and 4wd service light came on. will not turn off.
check 4wd light kept comping on and it would also shift very hard when buttons were pushed