Traction Control

The ABS module continuously monitors and compares the rotational speed of the drive wheels in relation to the non-driven wheels. When the drive wheels begin to spin faster than the non-driven wheels, the ABS module modulates brake pressure to the appropriate brake calipers by opening and closing the appropriate solenoid valves while activating the hydraulic pump motor. At the same time, the ABS module calculates how much engine torque reduction is required to eliminate the wheel slip and sends this torque reduction message to the PCM over the FD-CAN. The ABS module also sends a traction event message to the GWM over the FD-CAN which relays this message to the IPC over the HS-CAN3. When the PCM receives the torque reduction message, it adjusts engine timing and decreases fuel injector pulses to reduce the engine torque to the requested level. When the IPC receives the traction event message, it flashes the stability-traction control indicator (sliding car icon).

Once the driven wheel speed returns to the desired speed, the ABS module deactivates the hydraulic pump motor and solenoid valves, and stops sending the traction event and torque reduction messages. The PCM returns engine timing and fuel injectors to normal operation and the IPC extinguishes the stability-traction control indicator (sliding car icon). Once vehicle speed exceeds 100 km/h (62 mph), traction control is accomplished only through the PCM torque control.

On 4WD vehicles, the traction control system is disabled by the driver using the stability-traction control switch which is part of the AWDMSS. When the traction control switch is pressed, the ATCM sends a message to the ABS module over the FD-CAN and a message to the IPC through the GWM and over the HS-CAN3. The ABS module takes no further action in regards to traction control until the driver presses the switch again in the same ignition cycle or until the ignition is cycled from OFF to ON. The IPC responds by illuminating the stability-traction control disabled indicator (sliding car OFF icon).

Disabling the traction control system is independent of ABS which cannot be disabled by the driver. The ABS module disables traction control if there are any wheel speed sensor or solenoid valve Diagnostic Trouble Codes (DTCs) present in the ABS module. Traction control is also disabled if there is a communication error between the ABS module and the PCM. When traction control is disabled, the ABS module sends a message to the GWM over the FD-CAN. The GWM relays this message to the IPC over the HS-CAN3 to illuminate the stability-traction control indicator (sliding car icon).