Automatic Stability Control (ASC)

The ASC utilizes the ABS sensing arrangement to provide the maximum traction force to propel the vehicle.

The ASC is switched on when the engine is started. The system can be switched off by pressing the 'ASC OFF' (the switched is marked 'TRAC OFF' on vehicles fitted with traction control). The switch, which is situated in the center console switchpack, lights up to warn that the system is switched off. An 'ASC' amber warning light flashes on the instrument panel when the system detects a spinning wheel.

The ASC system uses engine intervention to reduce the torque delivered to the drive wheels to prevent them spinning.

Engine torque is reduced in three ways:

• The throttle is moved towards the closed position.
• The ignition is retarded.
• Fuel is cut-off at the cylinder injectors.

Wheel spin is detected by the wheel speed sensors and communicated to the ABS/TCCM. The ABS/TCCM uses information from the controller area network (CAN) to calculate the torque that the engine should produce to stop the wheel spinning.

Torque reductions are then requested from the engine control module (ECM) through the CAN. The throttle is then positioned to provide the target torque, which has been calculated to prevent wheel spin. During the transient phase of torque reduction the fuel is cut-off and the ignition retarded Both the fuel cut-off and ignition retard will be restored to normal when the throttle is set to its new position.

The ASC uses a brake control modulator with six solenoid valves: three normally open inlet valves and three normally closed outlet valves.