Discovery I (LJ) V8-3.9L (1994)
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Electronic Brake Control Module: Description and Operation
DESCRIPTION AND OPERATION
The Anti-Lock Brake System ECU (Z108) is a computer that controls ABS system operation by constantly monitoring the vehicle's 4 wheel speeds
when the ignition is in position II. If an impending wheel lock up is detected during this monitoring, the Anti-Lock Brake ECU will apply voltage
to the various inlet and outlet valve solenoids contained in the ABS Booster Unit (Z103). Operation of the solenoid valves regulates the pressure
applied to the each wheel brake caliper and therefore prevents wheel lock-up.
The Anti-Lock Brake System ECU (Z108) also has diagnostic capabilities that allow it to detect faults that may impair the system's efficiency. If a
fault occurs, the ECU informs the operator of a problem by illuminating on the ABS warning light. The ECU also illuminates the warning light
when the ignition is first placed in position II. The warning light will remain illuminated until the ECU completes a self check of the system. When
the ECU sees all wheels reach a speed of 7 kph (5 mph), the self check is completed and the warning light turns off. If a fault is detected during
the self check, the ABS warning light will remain on and a fault code will be stored in memory to aid in servicing the system. The fault code can
be retrieved using a diagnostic tester or by flashing the ABS warning light.
