Antilock Brake Light

NOTE: The Control unit used in this Anti-Lock brake system does not have On-Board Diagnostic capabilities and, consequently, does not store diagnostic trouble codes (DTC's)!

There is also no reset procedure for the Antilock Brake Light. In order for the Antilock Brake Light to go out, the system must pass the Self Tests.



SELF TESTS

Self test features are incorporated within the ECU which initiates a fail warning on the instrument pack when a system fault occurs. Testing is performed in three stages as follows:
- Initial tests.
- Low speed tests.
- Continueous tests.


INITIAL TESTS

These tests are performed when the vehicle ignition is switched 'on' and comprise the following:
- Simulated wheel speed sensor signals are generated and the input Circuits are checked for the correct response.
- The battery voltage is checked to ensure that it is greater than 10V.
- Wheel acceleration and deceleration levels are checked to ensure that they are set correctly.

If the initial tests are completed satisfactorily, a fail warning initiated when the ignition was switched 'on' is extinguished.


LOW SPEED TESTS

These tests are performed when the vehicle reaches a road speed of 3.6mph (5.75 kph) and are as follows:
- The modulator valves are actuated and monitored to ensure that the correct currents are flowing.
- The pump is actuated and its operation verified by the voltage developed across its windings when it is switched 'off'.

These tests occur only on the first occasion that the test speed is detected and are reset when the ignition is switched 'off'.


CONTINUOUS TESTS

These tests are performed when the vehicle is running and comprise the following:
- Each wheel speed sensor signal is monitored to ensure that it is within the expected range.
- The harness is checked to ensure no open or short circuit faults exist.