As an add-on logic to the antilock brake system (ABS) base algorithm, electronic brake force distribution (EBD) works in a range in which the intervention thresholds for ABS control are not reached yet.

EBD ensures that the rear wheels are sensitively monitored for slip with respect to the front axle. If slip is detected, the inlet valves for the rear wheels are switched to pressure hold to prevent a further increase in pressure at the rear-wheel brakes, thus electronically reproducing a pressure-reduction function at the rear-wheel brakes.

The BPMV/EBCM performs the following primary functions;

The BPMV/EBCM continuously checks the speed of each wheel to determine if any wheel is beginning to slip. If any wheel slip tendency is detected, the BPMV/EBCM commands appropriate valve positions to modulate brake fluid pressure in some or all of the hydraulic circuits to prevent wheel slip and provide optimum braking. The BPMV/EBCM continues to control pressure in individual hydraulic circuits until a slipping tendency is no longer present. Also the BPMV/EBCM continuously monitors the ABS for proper operation. If the BPMV/EBCM detects an error, it can disable the ABS function and turn on the ABS Warning Lamp in the instrument cluster. The BPMV/EBCM also controls the display of the ABS DTCs (Diagnostic Trouble Codes) while in diagnostic mode.

The solenoid relay, provides power to the pump motor and solenoids. The switch in the relay is normally open, but is commanded to close during initialization. The relay switch will remain closed for the remainder of the drive cycle as long as no DTCs (Diagnostic Trouble Codes) set which required the switch to open. If a DTC sets which requires the relay to be commanded off, battery voltage will be removed from the pump motor and solenoids for the remainder of the current drive cycle and ABS cannot function. The relay is an integral part of the BPMV/EBCM and cannot be serviced separately.

A wheel speed sensor is present at each wheel. The sensors transmit wheel speed information to the BPMV/EBCM by means of a small AC voltage. This voltage is generated by magnetic induction caused by passing a thoothed sensor ring past a stationary sensor. The magnitude and frequency of the AC voltage are proportional to the speed of the wheel and both will increase with increasing speed. The signal is transmitted to the BPMV/EBCM through interface that can cause false or noisy wheel speed sensor input to the BPMV/EBCM.

The ABS warning lamp is located in the instrument cluster and will illuminate if a malfunction in the ABS is detected by the BPMV/EBCM. The ABS warning lamp informs the driver that a condition exists which results in turning off the antilock brake function. If only the ABS is warning lamp is on, normal braking with full power assist is available.

Conditions for the ABS warning lamp to turn on are as follows.

The red brake warning lamp in the instrument cluster will illuminate to warn the driver of a condition in the brake system, which may result in reduced braking ability. The lamp will illuminate when the parking brake is applied or not fully released, or if the brake fluid level switch is closed (when the brake fluid is low in the master cylinder reservoir). When the brake fluid level switch is closed (low condition) a brake warning lamp will stay illuminated until the condition has been repaired. Also some failure modes in ABS system will illuminate the lamp to let the drivers know DDRP (De-coupled Dynamic Rear Proportioning) is disabled