Tractions Control System (TCS)

Traction Control Mode:

The Traction Control System (TCS) is an add on to the ABS VI Antilock brake system. The TCS provides the capability to control wheel spin at each driven wheel. This improves the ability to maintain vehicle stability and acceleration (drive traction) under changing road and vehicle load conditions.

Traction Control occurs when the Electronic Brake Traction Control Module (EBTCM) determines one or more of the drive wheels are accelerating too rapidly and the brake switch is off. The EBTCM processes wheel speed sensor data and sends commands to the Powertrain Control Module for torque reduction and to the TCS modulator to apply and release the brakes several times each second to reduce driven wheel speed a prescribed amount, providing stability and tractions.

If one or more of the wheels are accelerating too rapidly and the brake switcch is not applied, the EBTCM will control one or both of the TCS motors to apply and release brake pressure to the affected wheel(s). During TCS operation, the ball screws and pistons are driven upward from their home position. This process seats the popplet valve (thus isolating the master cylinder). The brake pressure to the wheel is now a function of the controlled volume within the piston chamber. The ball screws and pistons are driven by bi-directional motors, allowing for pressure to be applied, held, or released from the wheels.


TCS cannot be entered if base brakes or ABS are in operation. Base brakes and ABS take precedence over TCS in all conditions. If TCS is being utilized and base brake or ABS operation is called for (activated by the stoplamp switch), the TCS modulator assembly will immediately re-home the TCS ball screws and pistons. The applied brake pressure from the master cylinder can overcome the poppet valve spring to apply brake pressure immediately to the wheels during the re-home operation.

The PCM portion of the traction control system utilizes the PCM fuel and ignition controls to limit drive wheel slippage during acceleration by reducing engine torque. This is accomplished by retarding spark timing, and/or shutting off up to three fuel injectors.