System Operation: Operation
Spare Tire And Mismatched Tire Sizes
If the spare tire is installed, the AWD system may disable automatically and enter FWD only mode to protect driveline components. If the AWD systems detects 1 tire is 5% larger or smaller than the other tires, it may also disable the AWD system. This condition may be indicated by AWD OFF message in the message center. If there is a Check AWD 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 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. If this condition occurs, a DTC is set and a Check AWD message is displayed on the message center.
AWD Control And Fault Indicators
The AWD system consists of a power transfer unit (PTU) case, driveshaft, front and rear halfshafts, AWD relay module, Rear Drive Unit (RDU) with integral Active Torque Coupling (ATC) solenoid, and includes the PCM for AWD control logic. Using inputs from various module/systems, the PCM sends a command to the AWD relay module which controls the amount of torque sent to the rear wheels by sending a PWM duty cycle to the Active Torque Coupling (ATC) solenoid. AWD system faults are be indicated by a driveline icon indicator in the IPC as well as the Check AWD message in the message center.
Heat Protection - Rear Drive Unit (RDU)
During aggressive on road driving, the AWD system may implement a heat protection mode to protect the AWD clutch from damage. Without power transfer unit (PTU) or Rear Drive Unit (RDU) temperature sensors, the PCM performs calculations to determine the need for the heat protection mode. If the AWD system detects an overheat condition, it enters a locked mode. If the heat in the Rear Drive Unit (RDU) continues to rise once in the locked mode, the PCM disables the Active Torque Coupling (ATC) solenoid. This condition may be indicated by an AWD Temporarily Disabled message in the message center. To resume normal operation, stop the vehicle in a safe location and turn the engine off for at least 10 minutes. After the engine is restarted and the AWD system has adequately cooled down, the AWD Temporarily Disabled message turns off and normal AWD operation returns. In the event the engine is not stopped, the AWD Temporarily Disabled message turns off when the system cools. Normal AWD operation returns once the message center displays AWD Restored.
Heat Protection - Power Transfer Unit (PTU)
During excessive use or trailer towing the AWD system may implement a heat protection mode to protect the PTU from damage. Without power transfer unit (PTU) temperature sensors, the PCM performs calculations to determine the need for the heat protection mode. The AWD system reduces commanded torque only to situation deemed critical for minimal function. Once the maximum temperature limit is reached, then FWD only is commanded. The PTU on vehicles equipped with the 6F50/55 transmission is equipped with a temperature sensor.
AWD Bar Code Identification
The AWD system on this vehicle uses a solenoid to control the Active Torque Coupling (ATC). Due to response rate differences within the AWD hardware, the PCM must know the response rate of the ATC. This can be done by programming the ATC bar code data into the PCM. The PCM uses this bar code information to match the clutch characteristics of the ATC 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 PCM needs to be replaced, the new PCM needs to be configured with the existing ATC solenoid bar code information. If the rear drive axle need to be replaced, the existing PCM needs to be configured with the new ATC solenoid bar code information.
Automatic Torque Coupling Configuration Bar Code Label Location
Label Location
| Item | Description |
|---|---|
| 1 | Active Torque Coupling (ATC) solenoid bar code label |
Automatic Torque Coupling Configuration
Refer to: Active Torque Coupling Configuration .
AWD Drive Cycle
1. Carry out 3 accelerations from 0-30 mph (0-48 km/h) in a straight line.
- Perform this procedure at low, medium and full accelerator pedal position.
- Verify there is no perceived front wheel slip.
2. On dry pavement, drive the vehicle at 5 mph (8 km/h) in a fully locked turn.
- Verify there is no driveline binding.