Principles of Operation: Notes

The AWD system is an active system, which means it not only responds to wheel slip between the front and rear axles but also has the ability to anticipate wheel slip and transfer torque to the rear wheels before the slip occurs. The AWD system is active all the time and requires no input from the operator.

The AWD system continuously monitors vehicle conditions and automatically adjusts the torque distribution between the front and rear wheels. During normal operation, most of the torque is delivered to the front wheels. If wheel slip between the front and rear wheels is detected, if the vehicle is under heavy acceleration or if the vehicle is in an aggressive handling event, the AWD system increases torque to the rear wheels to prevent or control wheel slip. When the AWD system is functioning properly, there should be no perceived speed difference between the front and rear axles when launching or driving the vehicle on any uniform surface. Traction should be similar to a part time 4WD system in 4H (4X4 HIGH), but have no binding in turns.

If the compact spare tire is installed, the AWD system may disable automatically and enter FWD only mode to protect driveline components. This condition may be indicated by an AWD OFF message in the message center.

If there is an AWD OFF message in the message center from using the compact spare tire, this indicator should turn off after reinstalling the repaired or replaced normal road tire and cycling the ignition OFF and ON. It is recommended to reinstall the repaired or replaced road tire as soon as possible. Major dissimilar tire sizes between the front and rear axles could cause the AWD system to stop functioning and default to FWD or damage the AWD system.

AWD faults may be indicated by the powertrain malfunction (wrench) message center warning indicator in the IPC as well as the Check AWD message center warning indicator in the message center.

The AWD system consists of a PTU, driveshaft, front and rear halfshafts, AWD relay, PCM which includes the AWD control logic and an ATC solenoid located in the rear axle. Based on inputs to the PCM, the PCM sends a command to the AWD relay. The amount of torque sent to the rear wheels is controlled by the AWD relay sending a PWM duty cycle to the ATC solenoid.

The PCM also provides the brake system with its current clutch duty cycle and determines weather or not the brake system may take command of the clutch duty cycle.

NOTE: The ATC solenoid is not repairable. If a new component is required, the ATC solenoid and active torque coupling clutch are installed as an assembly. Refer to Rear Drive Axle Differential .

Specific inputs to the PCM are:

Accelerator pedal position via the High Speed CAN
TR via the High Speed CAN
Brake system status from the ABS module via the High Speed CAN
Wheel speed from all 4 wheels from the ABS module via the High Speed CAN

PCM outputs are:

Solid-state clutch PWM signal to the ATC solenoid
Percent of torque transfer commanded signal to the ABS module via the High Speed CAN
Torque request available signal to the ABS module via the High Speed CAN