Section 6 (Anti-Lock Brake System): Operation

WARNING: This page is about a different car, the 1999 GMC Sierra and 1999 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

When ignition is turned on, Yellow ANTI-LOCK and Red BRAKE warning lights will illuminate for 2 seconds as a bulb check. EBCM performs a self-check of the 4WAL system, once each ignition cycle, when vehicle speed reaches 8 MPH. If faults are detected by EBCM, ANTI-LOCK light will illuminate (in most cases). 4WAL functions will be disabled while ANTI-LOCK light is on. A related Diagnostic Trouble Code (DTC) will be stored. The Red BRAKE light illuminates if parking brake is applied or a mechanical brake problem is detected.

When brake pedal is depressed, brake switch voltage to EBCM drops from 12 volts to one volt. At this point, EBCM monitors wheel speed through an AC signal generated by speed sensors located at each wheel. If the deceleration rate of wheel speed reaches a preprogrammed rate, EBCM will activate various control valves to prevent wheel lock-up by increasing or decreasing hydraulic pressure to each channel: left front, right front or rear wheels.