Traction Control Mode

Traction Control Mode (Typical):

GENERAL INFORMATION
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 EBTCM determines one or more of the drive wheels are accelerating too rapidly and the brake switch is off. The Electronic Brake Traction Control Module (EBTCM) processes wheel speed sensor data and can control wheel slip by utilizing up to three different methods:
1. By commanding the Powertrain Control Module (PCM) to retard ignition timing, thereby reducing engine torque;
2. By utilizing the adjuster assembly motor to reduce the throttle angle, thereby reducing engine torque.
3. By brake intervention through the use of the TCS modulator.

COMPONENT OPERATION
The EBTCM can control one or both of the TCS motors simultaneously. The TCS motors are bi-directional and are used with the gear assemblies to drive the ball screws and pistons in the TCS modulator. The bi-directional motors allow pressure to be applied, held, or released from the wheels. During TCS operation, the ball screws and pistons are driven upward from their home position. This process seats the poppet valve (thus isolating the master cylinder). The brake pressure to the wheel is now a function of the controlled volume within the piston chamber. As drive wheel speed is reduced, the pistons are driven downward to their home position. This unseats the poppet valve and releases fluid pressure from the rear brake calipers. This process of apply, hold, and release can- repeat itself several times a second, until drive wheel speed is reduced a prescribed amount. The EBTCM also controls the adjuster assembly motor and sends commands via a Pulse Width Modulated (PWM) signal to the PCM to retard ignition timing, thereby reducing engine torque and wheel slip. TCS cannot be entered if the brake switch is on.

BASE BRAKE AND ABS OVERRIDE
Base brakes and ABS take precedence over TCS in all conditions. If TCS is being utilized and the brake switch is depressed, the EBTCM will immediately command the TCS motors to 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.