Traction Control System (TCS)

The Traction Control System (TCS) compares front wheel speeds to rear wheel speeds to determine if drive wheels lose traction. The TCS activates when drive wheel speed exceeds speed of non-drive wheels by a calibrated value. This allows the driver to maintain acceleration and directional stability while accelerating on low traction surfaces.

The TCS limits wheel slip during acceleration when one or more of the drive wheels lose traction. The brake switch must be off for TCS to operate.

The ABS control module monitors wheel speed output and compares drive wheel to non-drive wheel values to detect wheel slip. During a TCS event, the ABS control module sends a requested torque value to the ECM/TCM (L81) or PCM (L61). The ECM/TCM or PCM initiates an engine torque reduction routine to slow down the drive wheels. This routine consists of ignition timing reduction, fuel injector cut-off and transmission shift control. The ECM/PCM also sends a torque delivered value to the ABS control module. If the engine management routine is insufficient to achieve the desired wheel speed, the ABS control module will then use the TCS isolation valves and prime valves to slow down the drive wheels. The isolation valves close to isolate the wheel circuit from the master cylinder and the prime valves open to allow the motor-driven pump to access master cylinder fluid so it can build pressure to apply the desired brake.

If the ABS control module detects a malfunction, it will disable TCS and will command the BCM to turn the TRAC LED Off. The driver can also disable TCS, if desired, by depressing the TRAC switch. When the driver depresses the TRAC switch, the ABS control module will disable TCS and will command the BCM to turn the TRAC LED Off.