Principles of Operations

Principles of Operations

Anti-Lock Control
The ABS module receives wheel speed readings from each wheel speed sensor and processes this information to determine if an ABS event is necessary. The wheel speed sensor electrically senses each tooth of the wheel speed sensor indicators as it passes through the wheel speed sensor magnetic field.

The active wheel speed sensor generates a signal that is sent to the ABS module. The wheel speed sensor circuitry connects to the ABS module through 2 wires and a connector at each wheel speed sensor. When the ignition is turned to the RUN position, the ABS module carries out a self-test by sending a reference voltage to all of the wheel speed sensors through their circuitry to determine if they are functional.

The ABS module continuously monitors and compares the rotational speed of each wheel and when it detects an impending wheel lock, modulates brake pressure to the appropriate brake caliper. This is accomplished by triggering the hydraulic control unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS module returns the solenoid valves to their normal position, and normal (base) braking resumes.

The HCU has additional internal solenoid valves incorporated to enable control modulation of the wheel brake pressures.

The ABS module is self-monitoring. When the ignition switch is turned to the RUN position, the ABS module will do a preliminary electrical check of the wheel speed sensors by sending voltage through the sensor and checking for the voltage to return. At speeds above 20 km/h (12 mph), without the brake pedal being pressed, the pump motor will be commanded ON for approximately 1/2 second to check pump motor operation. Also, during all phases of operation the ABS module, with the vehicle in motion, checks for correct operation of the wheel speed sensors. Any malfunction of the ABS will cause the ABS to deactivate. Normal power assisted braking, however, remains.

Traction Control System - Front Wheel Drive (FWD)
The traction control system is designed to limit wheel spin by modulating engine torque, in order to achieve maximum traction, when driving on slippery or loose surfaces. On front wheel drive (FWD) vehicles, the ABS module sends the PCM wheel speed information over the high-speed controller area network (HS-CAN) bus. The PCM uses this information to determine if traction control is necessary. When the drive wheels lose traction and begin to spin at different speeds than the non-drive wheels, the PCM reduces engine torque to maintain vehicle traction by minor incremental timing changes and fewer fuel injector pulses until the speed of the driven wheels return to the desired speed. The PCM also sends a request to the instrument cluster to flash the traction control indicator.

The traction control system can be disabled by pressing the traction control switch and is indicated by the traction control indicator in the instrument cluster. The traction control system will reset and return to normal operation when the ignition switch is cycled or when the traction control switch is pressed and released a second time during the same ignition cycle.

Traction Control System - All Wheel Drive (AWD)
The traction control system is designed to limit wheel spin by modulating engine torque, in order to achieve maximum traction, when driving on slippery or loose surfaces. On all wheel drive (AWD) vehicles, the ABS module communicates with the PCM to assist with traction control. When the drive wheels lose traction and begin to spin at different speeds than the non-drive wheels, with vehicle speed under 100 km/h (62 mph), the ABS module requests the PCM to reduce engine torque while simultaneously activating the HCU to apply and release the appropriate brake caliper(s) to maintain vehicle traction. The PCM reduces engine torque by minor incremental timing changes and fewer fuel injector pulses until the ABS module ends the traction control request. The request ends when the speed of the driven wheels return to the desired speed. After the vehicle speed exceeds 100 km/h (62 mph), traction control is accomplished only through the PCM torque control.

The traction control system can be disabled by pressing the traction control switch and is indicated by the traction control light in the instrument cluster. The traction control system will reset and return to normal operation when the ignition switch is cycled or when the traction control switch is pressed and released a second time during the same ignition cycle.

ABS Module Configuration
ABS module configuration is not required on this vehicle.

Traction Control System Configuration - Front Wheel Drive (FWD)
The traction control system, for front wheel drive (FWD) vehicles, is contained in the PCM and is configured when the PCM is configured. Refer to Programmable Module Installation in Information Bus (Module Configuration).

Traction Control System Configuration - All Wheel Drive (AWD)
Traction control system configuration is not required on all wheel drive (AWD) vehicles.