All-Wheel Drive (AWD)

WARNING: This page is about a different car, the 2013 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

The vehicle is equipped with an AWD system that continuously monitors vehicle conditions and automatically adjusts the power distribution between the front and rear wheels. The system is always active and only requires the operator to select terrain.

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, the PCM commands torque delivery 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.

All AWD control logic resides in the PCM . The PCM continuously calculates if torque is required at the rear wheels and when torque is required, sends a low-current PWM signal to the AWD relay module over a hard wired circuit. The AWD relay module then outputs a high-current PWM signal which varies the current and duty cycle sent to the ATC solenoid, which is located inside the rear axle.

The PWM current supplied to the ATC solenoid increases as demand for rear wheel torque increases. The AWD relay module returns a signal to the PCM throughout AWD operation over a hard-wired circuit to monitor system capabilities.

AWD faults are indicated by the powertrain malfunction (wrench) warning indicator in the IPC as well as the CHECK AWD warning indicator in the message center.

A spare tire of a different size other than the tire provided should never be used. A dissimilar spare tire size (other than the spare tire provided) or major dissimilar tire sizes between the front and rear axles could cause the AWD system to stop functioning correctly. If the incorrect spare tire or dissimilar tire sizes between the front and rear axles is installed, the AWD system disables automatically and enters FWD only mode to protect driveline components. This condition could 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 message should disappear after reinstalling the repaired or replaced normal road tire and driving a short distance. It is recommended to reinstall the repaired or replaced road tire as soon as possible.

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

The active, on-demand AWD system uses data from other systems as inputs to the PCM . The PCM uses the inputs to determine the appropriate duty cycle to send to the AWD relay module and ATC solenoid that delivers the desired torque to the rear wheels. Specific inputs to the PCM are:

ATCM switch mode via the HS-CAN .
Engine off status from the BCM-B via the HS-CAN .
Steering wheel angle from the ABS module via the HS-CAN
Yaw rate and Lateral acceleration from the Restraints Control Module via the HS-CAN .
Brake system status from the ABS module via the HS-CAN .
Wheel speed from all 4 wheels from the ABS module via the HS-CAN .
AWD relay module diagnostic.

PCM outputs are:

PWM signal to the AWD relay module to the ATC solenoid for control of the solid-state clutch.
Amount of torque transfer commanded signal to the ABS module via the HS-CAN .
AWD system information to the IPC via the HS-CAN .
Returns terrain mode status and ready for change information to the ATCM via the HS-CAN .