Anti-Lock Brake System/Vehicle Skid Control: Description: Notes
ABS/VSC system consists of a number of different integrated systems: Anti-lock Brake (ABS), Electronic Brake Distribution (EBD), Brake Assist (BA), Traction Control (TRAC) and Vehicle Stability Control (VSC). For a breakdown of individual system functions, see SYSTEM FUNCTIONS .
There are 5 different warning lights that can indicate system malfunctions: ABS, VSC, VSC OFF, SLIP and BRAKE warning light. See Fig 1. Indicator lights come on for 3 seconds as a bulb test when ignition is turned on. All systems and warning lights are centrally controlled by a Skid Control ECU (ABS & BA & TRAC & VSC ECU). It is linked to a translate ECU (TL ECU), which is used to communicate with engine management system.
Each wheel has a speed sensor that feeds information back to Skid Control ECU. Under various conditions, brakes are applied or released through an ABS/VSC actuator. A solenoid relay and motor relay are used by Skid Control ECU to control operation of the actuator. For a complete ABS/VSC component description, see Fig 2.
A primary system check is performed after each engine start and when initial vehicle speed exceeds 6 MPH. ABS actuator noise may be heard during this time. A clicking noise may occur in engine compartment when engine is started. This noise is the ABS/VSC system performing an initial diagnostic check. These noises are normal.