Ford Fusion: Four-Wheel Drive Systems / Four-Wheel Drive Systems - System Operation and Component Description. Description and Operation

System Operation

System Diagram

Network Message Chart

  Module Network Input MessagesPCM

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

Automatic Torque Coupling Configuration

NOTICE: If the Active Torque Coupling (ATC) solenoid bar code information is not correct, Rear Drive Unit (RDU) damage or driveability concerns can occur.

NOTE: The 4-digit alpha numeric bar code is located on the label attached to the Rear Drive Unit (RDU).

Refer to: Active Torque Coupling Configuration (308-07A Four-Wheel Drive Systems, General Procedures).

AWD Drive Cycle

NOTE: Always drive the vehicle in a safe manner according to driving conditions and obey all traffic laws.

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.

Component Description

PCM

The PCM is the logic module for the four-wheel drive system. Multiple modules/system inputs are used for the four-wheel drive system to determine the percentage of torque to be transferred to the rear wheels.

Power Transfer Unit

The power transfer unit (PTU) is a gearbox that attaches to the transmission. The PTU directs power to the rear driveshaft and the Rear Drive Unit (RDU). For more information on the PTU,
Refer to: Power Transfer Unit (308-07B Power Transfer Unit - 6-Speed Automatic Transmission – 6F35, Diagnosis and Testing).
Refer to: Power Transfer Unit (308-07C Power Transfer Unit - 6-Speed Automatic Transmission – 6F50/6F55, Diagnosis and Testing).

AWD Relay Module

The AWD relay module receives the command from the PCM, and in turn supplies a PWM output to the Automatic Torque Coupling (ATC) solenoid for the requested torque to be applied.

Automatic Torque Coupling (ATC) Solenoid

The Automatic Torque Coupling (ATC) solenoid is integral to the Rear Drive Unit (RDU), and applies clutch pressure as controlled by the AWD relay module to increase or decrease torque to the rear wheels. The Rear Drive Unit (RDU) transfers torque from the drive shaft to the rear wheels depending on the specific request from the FWD system module ( PCM). The Rear Drive Unit (RDU) and Automatic Torque Coupling (ATC) solenoid are serviced in Chassis, Driveline section.
Refer to: Rear Drive Axle and Differential (205-02 Rear Drive Axle/Differential, Diagnosis and Testing).