Principles of Operation
The AWD system may be referred to as a 4WD system in other service information and owner literature.
The vehicle is equipped with an AWD system that is always active and requires no driver input.
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, or if the vehicle is under acceleration or if the vehicle is in a handling event, the AWD system increases and distributes torque to the rear wheels as needed. 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 non-uniform surface. Traction should be similar to a part time 4WD system in 4H (4X4 HIGH), but have no binding in turns.
If the spare tire is installed, the AWD system may disable automatically and enter FWD 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 spare tire, this indicator should turn off after reinstalling the repaired or replaced normal road tire and cycling the ignition off and then on. It is recommended to reinstall the repaired or replaced road tire as soon as possible. If the tire size used on the front differ greatly from the rear the AWD system may stop functioning and default to FWD or damage to the AWD system. If this condition occurs, a DTC is set and a AWD message is displayed in the message center.
AWD faults will 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 module, 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 module. The amount of torque sent to the rear wheels is controlled by the AWD relay module sending a PWM duty cycle to the ATC solenoid.
The AWD system processes data from other systems to determine the appropriate duty cycle to the AWD relay module and the ATC solenoid.
PCM inputs are:
- Steering wheel angle from the SCCM via the HS-CAN
- Lateral acceleration and yaw rate from the RCM via the HS-CAN
- Brake system status from the ABS module via the HS-CAN
- Wheel speed from the ABS module via the HS-CAN
- AWD relay module diagnostic
PCM outputs are:
- PWM signal to the AWD relay module
- Torque transfer commanded signal to the ABS module via the HS-CAN
Heat Protection RDU
During off-road operation, the AWD system may implement a heat protection mode to protect the AWD clutch from damage. If the AWD system detects an overheat condition, it enters a locked mode. If the heat in the RDU continues to rise once in the locked mode, the AWD relay module disables the ATC solenoid. This condition may be indicated by an AWD OFF message in the message center. Allow the AWD system to cool down at least 10 minutes with the ignition switch in the ON position.
AWD Bar Code Identification
The AWD system on this vehicle is equipped with a bar coded ATC solenoid to reduce the tolerance of electrical current to torque delivered to the ATC solenoid. The active torque control coupling solenoid bar code can be found etched on the active torque control coupling solenoid wire harness connector protruding from the top of the rear drive axle. The PCM uses this bar code information to match the clutch characteristics of the active torque control coupling solenoid with the desired output torque. If the bar code information does not match the PCM information, driveline damage or driveability concerns can occur. Therefore, if the rear drive axle needs to be replaced, the PCM will need to be configured with the ATC solenoid bar code information. Carry out the AWD Drive Cycle.
| Item | Description |
|---|---|
| 1 | ATC solenoid bar code |
AWD Drive Cycle
Carry out the AWD drive cycle after downloading the ATC solenoid bar code information to the PCM.