Test E: Controller Area Network (CAN) Communications Bus Fault

Test E: Controller Area Network (CAN) Communications Bus Fault

Refer to Vehicle/Diagrams, All Wheel Drive (AWD) Systems for schematic and connector information.

Normal Operation
The on-demand four wheel drive (4WD) system uses data from other systems as inputs to the 4WD control module. The 4WD control module uses the inputs to determine the appropriate duty cycle to send to the active torque coupling that delivers the desired torque to the rear wheels. Specific inputs to the 4WD control module are: accelerator pedal position output from the powertrain control module (PCM), transmission range from the transmission control module (TCM), brake system status and all 4 wheel speeds from the anti-lock brake system (ABS) module. Communication between the 4WD control module and other modules is obtained through the high speed controller area network (CAN). If the 4WD control module loses communication with, or receives invalid data from any of the necessary modules, diagnostic trouble codes (DTC's) are set and the 4WD control module may not allow 4WD operation.

Possible Causes
- 4WD control module
- PCM
- TCM
- ABS module
- Circuit VDB04 (WH/BU) open or short
- Circuit VDB05 (WH) open or short
- CAN bus fault

NOTE: Conduct Steps 1 through 10 outlined in Inspection and Verification prior to carrying out this test. Inspection and Verification

E1-E2:

E2-E4:

E5-E8: