ABS System Self-Diagnostics

GENERAL INFORMATION
The ITT Teves Mark 20 ABS system is equipped with a self diagnostic capability which may be used to assist in the isolation of ABS faults. The features of the self diagnostics system are described below.

START-UP CYCLE
The self diagnostic ABS start up cycle begins when the ignition switch is turned to the on position. Electrical checks are completed on ABS components, such as the Controller, solenoid continuity, and the system relay operation. During this check the Amber ABS Warning Light is turned on for approximately 5 seconds and the brake pedal may emit a popping sound and move slightly when the solenoid valves are checked.

DRIVE-OFF CYCLE
Further Functional testing is accomplished once the vehicle is set in motion and reaches a speed of about 20 kph (12 mph.). This cycle is performed only once after each ignition on/off cycle.
- The pump/motor is activated briefly to verify function. When the pump/motor is activated a whirling or buzzing sound may be heard by the driver, which is normal when the pump/motor is running.
- The wheel speed sensor output is verified to be within the correct operating range.

ONGOING TESTS
Other tests are performed on a continuous basis. These include checks for solenoid continuity, wheel speed sensor continuity and wheel speed sensor output.