Operation - Abs With Traction Control System (TCS)
Traction Control System operates as an addition to the Anti-Lock Brake System. Initialization, warning light operation, control module and sensor operation are all identical. A separate TCS warning light is used, but the parameters of operation and action are the same.
As with the Anti-Lock Brake System, during normal driving conditions, the vehicles brakes operate like a conventional brake system. The EBTCM constantly monitors wheel speed signals for both ABS and TCS operation. If either or both drive wheels slip, the corresponding wheel speed sensor(s) signals will not match the others, and the EBTCM will determine that traction control is required.
The EBTCM achieves traction control by rapidly pulsing brake pressure to the affected wheel or wheels; and by commanding PCM to retard spark timing and, if necessary, shut off up to three injectors to limit the engine torque until traction is regained. Brake application during traction control is accomplished through a TCS hydraulic modulator. When the EBTCM commands traction control, the TCS hydraulic modulator has internal pistons which are driven by bi-directional motors to allow for rapid pulsation of hydraulic pressure to individual wheels. When in operation, the piston action closes a poppet valve which isolates the master cylinder from the affected wheel.
If, during TCS operation, conventional braking is required, the driver applies the brakes, and the hydraulic pressure of the master cylinder is sufficient to overcome the poppet valve. In this way, conventional braking and ABS operation take priority over traction control.
During a traction control or anti-lock event, and for several seconds after, the ABS/TCS active lamp ("LOW TRACTION" or "TRAC CTL ON") will light. If a malfunction occurs, "TCS" or "SERVICE TRAC CTL" light will come on, and traction control will be unavailable until system is repaired. If EBTCM determines malfunction will limit operation of ABS, both lights will come on and both systems will be disabled.