System Self-Diagnostics: Overview

The ABS system has been designed with self diagnostic capability. There are two self checks the systems performs every time the vehicle is started. First, when the key is turned on, the system performs an electrical check called START-UP CYCLE. During this check, the (BRAKE) warning lamp and the (ANTI-LOCK) warning lamp are illuminated, and then turned off at the end of the test, after about 1 to 2 seconds. As soon as the vehicle reaches a speed of about 3 to 4 miles per hour, the system performs a functional check called DRIVE-OFF. During DRIVE-OFF. hydraulic valves are activated briefly to test their function.
DRIVE-OFF can be detected as a series of rapid clicks upon driving off the first time the car is started. If the brake pedal is applied during DRIVE-OFF, the test is by-passed. Both of these conditions are a normal part of the system self test. Most fault conditions will set an ABS Fault Code in the (CAB), which can be retrieved to aid in fault diagnosis. Details can be found in Section 2-Diagnosis.