All Wheel Drive (AWD) Systems

Principles of Operation

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 heavy acceleration or if the vehicle is in an aggressive handling event, the AWD system increases torque 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.

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 may 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, 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. The amount of torque sent to the rear wheels is controlled by the AWD relay sending a PWM duty cycle to the ATC solenoid.

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

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 Section 205-02 .

Specific inputs to the PCM are:

• Accelerator pedal position via the High Speed CAN
• TR via the High Speed CAN
• Brake system status from the ABS module via the High Speed CAN
• Wheel speed from all 4 wheels from the ABS module via the High Speed CAN

PCM outputs are:

• Solid-state clutch PWM signal to the ATC solenoid
• Percent of torque transfer commanded signal to the ABS module via the High Speed CAN
• Torque request available signal to the ABS module via the High Speed CAN

Heat Protection Mode

During very extreme off-road operation, the AWD system utilizes a heat protection mode to protect the ATC solenoid from damage. If the AWD system detects an overheat condition, it enters a locked mode. If the heat in the AWD system continues to rise once in the locked mode, the PCM disables the ATC solenoid. This condition may be indicated by an AWD OFF message in the message center. To resume normal AWD function as soon as possible, stop the vehicle in a safe location and stop the engine for at least 10 minutes. After the engine is restarted and the AWD system has adequately cooled down, the AWD OFF message will turn off and normal AWD operation will return. In the event the engine is not stopped, the AWD OFF message will turn off when the system cools and normal AWD operation returns.

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 by the ATC solenoid. The ATC solenoid bar code can be found etched on the ATC solenoid wire harness connector protruding from the top of the rear drive axle or on the RDU . 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 will need to be configured with the existing ATC solenoid bar code information. If the rear drive axle need to be replaced, the existing PCM will need to be configured with the new ATC solenoid bar code information. Carry out the AWD Drive Cycle.

Steel Cover RDU

Aluminum Cover RDU

AWD Drive Cycle

Carry out the AWD drive cycle after downloading the ATC solenoid bar code information to the PCM.

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

1. Carry out 3 accelerations from 0-48 km/h (0-30 mph) in a straight line.
   • Perform this procedure at low, medium and full accelerator pedal position.
   • Verify that there is no perceived front wheel slip.

2. On dry pavement, drive the vehicle at 8 km/h (5 mph) in a fully locked turn.
   • Verify that there is no driveline binding.

Inspection and Verification

1. Verify the customer concern.

2. Inspect for obvious signs of mechanical or electrical damage.

  Visual Inspection Chart

3. If the DTCs retrieved are related to the concern, go to the DTC Chart. For all other DTCs, refer to Section 419-10 .

4. If no DTCs related to the concern are retrieved, GO to Symptom Chart .

DTC Chart

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for more information.

 DTC Chart - PCM

Symptom Chart

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for more information.

In most circumstances, the PCM sets DTCs to help guide with diagnostics. Refer to the DTC Chart before using the symptom chart. The Condition column lists the vehicle condition. The Source column lists a detailed vehicle condition. The Action column lists the action to be performed to determine the cause of the condition. Each action lists the components that can caused the system and the individual components in that system. The components are listed in order of disassembly. Use the list of components and the required action to focus on disassembly inspections for the root cause of the concern.

Pinpoint Tests

Pinpoint Test A: AWD System Functional Test

Diagnostic Overview

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for more information. This pinpoint test is intended to diagnosis the AWD system concern without on-demand or continuous DTCs

Refer to Wiring Diagrams Cell 34 , All Wheel Drive (AWD) for schematic and connector information.

Normal Operation and Fault Conditions

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 heavy acceleration or if the vehicle is in an aggressive handling event, the AWD system increases torque 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.

PINPOINT TEST A: AWD SYSTEM FUNCTIONAL TEST

 WARNING: When directed to drive the vehicle as part of this test, drive the vehicle on a hard surface in an area without traffic to prevent a crash. Failure to follow these instructions may result in personal injury.

Pinpoint Test B: P187B

Diagnostic Overview

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for information about these practices. This pinpoint test is intended to diagnosis the wheels and tires, wheel speed sensors ABS module and PCM.

Refer to Wiring Diagrams Cell 34 , All Wheel Drive (AWD) for schematic and connector information.

Normal Operation and Fault Conditions

The AWD system uses input data from the ABS module wheel speed sensor inputs to the PCM. A dissimilar spare tire size (other than the spare tire provided) or major dissimilar tire sizes or improperly inflated tires between the front and rear axles could cause the AWD system to stop functioning correctly.

 DTC Fault Trigger Conditions

PINPOINT TEST B: P187B

 WARNING: When directed to drive the vehicle as part of this test, drive the vehicle on a hard surface in an area without traffic to prevent a crash. Failure to follow these instructions may result in personal injury.

Pinpoint Test C: P188B

Diagnostic Overview

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for information about these practices. This pinpoint test is intended to diagnosis the wiring, terminals, connectors, AWD relay and PCM.

NOTE: Fuse 70 (15A) is HOT at all times and protects multiple components. Check related systems that may be inoperative.

Refer to Wiring Diagrams Cell 34 , All Wheel Drive (AWD) for schematic and connector information.

Normal Operation and Fault Conditions

The AWD system uses data from other systems as inputs to the PCM. The PCM uses the inputs to determine the appropriate time to send a signal and have the AWD relay energize the ATC solenoid.

 DTC Fault Trigger Conditions

PINPOINT TEST C: P188B

Pinpoint Test D: P188C and P188D

Diagnostic Overview

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for information about these practices. This pinpoint test is intended to diagnosis the wiring, terminals, connectors, AWD relay and PCM.

NOTE: Fuse 70 (15A) is HOT at all times and protects multiple components. Check related systems that may be inoperative.

Refer to Wiring Diagrams Cell 34 , All Wheel Drive (AWD) for schematic and connector information.

Normal Operation and Fault Conditions

The 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 on the command circuit and returns AWD relay information on the feedback circuit.

 DTC Fault Trigger Conditions

PINPOINT TEST D: P188C AND P188D

Pinpoint Test E: Vehicle Binds in a Turn or Resists Turning/Pulsates or Shudders in a Straight Line

Diagnostic Overview

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for information about these practices. This pinpoint test is intended to diagnosis the wiring, terminals, connectors, wheels and tires, rear axle, ABS module, PCM and AWD relay.

Refer to Wiring Diagrams Cell 34 , All Wheel Drive (AWD) for schematic and connector information.

Normal Operation and Fault Conditions

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 heavy acceleration or if the vehicle is in an aggressive handling event, the AWD system increases torque 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.

PINPOINT TEST E: VEHICLE BINDS IN A TURN OR RESISTS TURNING/PULSATES OR SHUDDERS IN A STRAIGHT LINE

 WARNING: When directed to drive the vehicle as part of this test, drive the vehicle on a hard surface in an area without traffic to prevent a crash. Failure to follow these instructions may result in personal injury.