Service 4WD Light On And The System Inoperative Switch Contamination - keywords axle case differential lock transfer

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some customers may comment about a Service 4WD Light on and transfer case or rear differential lock system inoperative. Technicians may find various switch DTCs or open fuses and the transfer case select switch contaminated

A number of 4WD switches have been received through the Warranty Parts Center that show obvious signs of contamination caused by liquids being spilled through the HVAC vents. On an H3 vehicle these liquids will run in behind the IP face plate and leak into the 4WD switch, the radio and if severe enough may also cause various fuses to become open.

In particular, liquid air fresheners that clip onto the HVAC vents can spill onto the IP components. Air fresheners will chemically blister the paint on the 4WD switch and cause the buttons to stick. A B2725 or B0790 switch DTC may be set. The switch may also smell like perfume. Additional paint blistering may occur on the radio.

The affected components will have to be replaced. However, contamination of this nature does not constitute a defect in materials or workmanship for which General Motors would be responsible. Each suspect vehicle should be carefully inspected and a decision made at the local level regarding GM participation with the repair expenses.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.