ABS Operation

When ignition switch is turned to ``On'' position, amber ANTILOCK warning lamp in instrument panel lights. When engine is started, it goes out. If ABS warning light does not go out or comes on suddenly while driving, it indicates a fault in ABS system.
When starting vehicle, the control module performs a functional check of electrical circuitry. The test cycle itself checks components of monitoring circuit as well as the logic section. For this purpose, control module is fed with given test sample signals to check whether correct output signals are available.
Since the ABS system may not be used every day, there is an additional test which actually runs modulator function. This is done once each time ignition is turned on to ensure system is functioning properly. Whenever ignition switch is turned to ``On'' position and vehicle reaches 4 mph, the test starts.
This system continuously monitors the following components: modulator valve, control modulator, lateral acceleration switch, wheel speed sensors and wiring harness and relays.
The control module also constantly monitors its own supply voltage. If supply voltage drops below a predetermined value, ABS will be switched off and the amber ANTILOCK lamp will come on. When supplied voltage returns to or exceeds a predetermined value, lamp will go off. If a fault occurs in ABS, ANTILOCK warning lamp comes on and ABS will be switched off. The system will remain off until vehicle is restarted at which time functional check is repeated.