Anti-Lock/Traction Control: Operation

As vehicle is moving, wheel sensors send an AC voltage signal to ABS/TCS control unit. Control unit monitors brakelight switch to determine when brake pedal is pressed. When brake pedal is pressed, ABS/TCS control unit monitors signals from each speed sensor to determine rate of deceleration.

If rate of deceleration from any speed sensor reaches a preprogrammed rate, ABS/TCS control unit activates solenoid valves inside actuator. Solenoid valves are cycled to apply, release or maintain hydraulic pressure to each wheel in any combination.

Regulating hydraulic pressure to each circuit prevents wheel lock-up. When brake pedal is released, ABS/TCS control unit deactivates solenoid valves, returning brake system to conventional mode until ABS is needed. ABS will not operate when vehicle speed is less than 6 MPH.

A slight vibration and noise may be noticed during hard braking. These conditions are normal and indicate anti-lock brake system is functioning properly. If a malfunction in ABS system is detected by ABS/TCS control unit, ABS system will be deactivated, ABS warning light will turn on and conventional brake system will operate normally.

Drive wheel slippage is detected by wheel sensors. When wheel slip becomes excessive, SLIP light flashes. ABS/TCS control unit sends a fuel cut signal to Engine Control Module (ECM) and a signal to change shift points is sent to Transmission Control Module (TCM). If fuel cut continues for an extended period of time during high speed driving, the system will cancel the fuel cut function to prevent catalyst damage.

When TCS OFF switch is used to deactivate TCS operation, TCS OFF indicator turns on and TCS does not operate. If a malfunction in TCS system is detected by ABS/TCS control unit, TCS system will be deactivated and both TCS OFF light and SLIP light will turn on.