Principles of Operation: Notes

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 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 acceleration or if the vehicle is in an 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 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 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 PCM provides the brake system with its current clutch command torque level and determines wether or not the brake system may take command of the AWD clutch.

NOTE: The ATC solenoid is not repairable. If a new component is required, the ATC solenoid and rear axle are installed as an assembly. Refer to REAR DRIVE AXLE/DIFFERENTIAL .

PCM inputs are:

Various engine and transmission signals received internally
Various signals received internally via HS CAN from the ABS module
Diagnostic information from the AWD relay module

PCM outputs are:

Solid-state clutch PWM signal to the ATC solenoid