Traction Control Module: Description and Operation

ABS/TCS CONTROL MODULE DESCRIPTION





Outline
^ The TCS control module is integrated with the ABS, and the integrated module is installed on the lower part of the ABS hydraulic unit.
^ Each wheel's speed signal, and various types of switch inputs for judging the vehicle's condition are input to the ABS/TCS control module. If the ABS/TSC control module detects from these signals that the drive wheels are spinning, it sends a torque reduction request signal appropriate to the traveling conditions to the Powertrain Control Module (PCM). The PCM restrains engine output in accordance with the torque reduction request signal.
^ The ABS/TCS control module has fail-safe and on-board diagnosis functions. When it detects a malfunction inside the system, it stops TCS operation and illuminates the TCS OFF light and TCS indicator light to inform the driver that there is a malfunction. The malfunction is memorized by the TCS/ABS control module. In the diagnosis mode, the ABS/TCS control module outputs the diagnostic trouble code for the malfunction via the data link connector.





System Control

Control during straight travel
^ The ABS/TCS control module computes the speeds of the 4 wheels.
^ If the drive wheel speed exceeds the driven wheel speed by more than the regulation amount, the ABS/TCS control module judges that slipping has occurred, and starts control.
^ When control starts, the ABS/TCS control module decides the optimum amount of engine torque reduction for the amount of slippage, and sends signals communicating this torque reduction amount to the PCM.
^ In accordance with these signals, the PCM executes torque reduction by fuel cuts and retarding ignition timing.

Control During Turning
^ The ABS/TCS control module uses the steering angle from the wheel speed to calculate the lateral G in the vehicle. The larger this lateral G is, the more traction is controlled and lateral force is increased.
^ That is, the larger the lateral G is, the lower the target slip ratio is made, and traction is controlled so that it is on the driving stability side of the range.

Other Control
^ This system is automatically ready for operation as soon as the engine is started, but a TCS OFF switch is installed that enables the driver to deactivate TCS control if desired.
^ However, when this switch is used, if the ABS/TCS control module detects that the vehicle is traveling on a slippery road surface, the TCS system will be deactivated only after it has completed its operation. And in order to protect the engine, if engine coolant temperature is extremely low, TCS control is temporarily interrupted until the engine coolant temperature rises. In such cases, the TCS OFF light will be illuminated.

Fall-Safe Function
^ The ABS/TCS control module has a fail-safe function. When this function senses a malfunction in the ABS, the ABS returns to normal braking and the ABS warning light illuminates. At this time, the TCS OFF light and the TCS indicator light also illuminate and TCS operation is inhibited until the ignition switch has been turned off.
^ When a malfunction is detected in the TCS, the torque reduction request signals are fixed at 0, and the TCS OFF and TCS indicator light are illuminated simultaneously.