If during the pressure hold mode the electronic brake control module (EBCM) still senses wheel slip, the EBCM will decrease the pressure to the affected wheels. The inlet valve is left closed and the outlet valve is opened. The excess fluid/pressure is temporarily stored into an accumulator within the brake pressure modulator valve (BPMV), until the pump can return the fluid to the master cylinder reservoir.

De-coupled dynamic rear proportioning (DDRP) is a proportioning system to maintain vehicle stability during braking. In normal braking condition, equal wheel speed should be maintained for efficient and balanced braking. In hard braking conditions, a vehicle requires relatively less brake force at rear wheel due to vehicle's weight transfer to the front. DDRP maintains desired brake pressure to the rear wheel by using the antilock brake system (ABS) rear inlet and outlet valve in order to provide efficient braking and vehicle stability. In the DDRP system, the power to the rear hold valve solenoid is provided from the ignition. If the following fault conditions are existing, the red brake warning lamp will be illuminated.

The electronic brake control module (EBCM) performs the following primary functions in order to provide efficient braking and vehicle stability. In the de-coupled dynamic rear proportioning (DDRP) system, power to the rear hold valve solenoid is provided from the ignition. If the following fault conditions are existing, the red brake warning lamp will be illuminated.

The 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 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 EBCM continues to control pressure in individual hydraulic circuits until a slipping tendency is no longer present. Also the EBCM continuously monitors the ABS for proper operation. If the EBCM detects an error, it can disable the antilock brake system (ABS) function and turn ON the ABS warning lamp in the instrument cluster. The EBCM also controls the display of the ABS DTCs 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 diagnostic trouble codes (DTCs) set which require 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 antilock brake system (ABS) cannot function. The relay is an integral part of the electronic brake control module (EBCM) and cannot be serviced separately.

A wheel speed sensor is present at each wheel. The sensors transmit wheel speed information to the electronic brake control module (EBCM) by means of a small alternating current (AC) voltage. The signal is transmitted to the EBCM through interface that can cause false or noisy wheel speed sensor input to the EBCM.

The antilock brake system (ABS) warning lamp is located in the instrument cluster and will illuminate if a malfunction in the ABS is detected by the electronic brake control module (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 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 is in the instrument cluster and will illuminate to warn the driver of abnormal conditions 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. Closed is 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 MGH-25 system will illuminate the lamp to let the driver know de-coupled dynamic rear proportioning (DDRP) is disabled.

When drive wheel slip is noted while the brake is not applied, the electronic brake control module (EBCM) will enter traction control mode.

For the North American system, the EBCM requests the engine control module (ECM) to reduce the amount of torque to the drive wheels via the CAN communication circuit. The ECM reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The ECM reports the amount of torque delivered to the drive wheels via the delivered torque signal circuit.

If the engine torque reduction does not eliminate drive wheel slip, the EBCM will actively apply the drive wheel brakes only.

For non North American application, traction control is controlled by actively applying the drive wheel brakes only.

During traction control braking, both applications, hydraulic pressure in each drive wheel circuit is controlled to prevent the drive wheels from slipping. The master cylinder isolation valve closes in order to isolate the master cylinder from the rest of the hydraulic system. The prime valve then opens in order to allow the pump to accumulate brake fluid in order to build hydraulic pressure for braking. The drive wheel inlet and outlet solenoid valves then open and close in order to perform the following functions:

TCS Warning Lamp

The electronic brake control module (EBCM) illuminates the TCS Warning indicator when the EBCM detects a malfunction in the traction control system (TCS). The EBCM supplies a ground signal to the instrument panel (I/P) cluster to illuminate the TCS Warning lamp.

The TCS Warning lamp indicator illuminates under the following conditions:

TCS Active Lamp

The TCS Active lamp illuminates when the ignition is first turned ON for 3 seconds along with the ABS lamp, and then both lamps will turn OFF.

The TCS Active lamp will blink when the traction control system (TCS) is operating. When the electronic brake control module (EBCM) detects a wheel spin condition, the EBCM will activate the TCS and blink the TCS Active lamp as long as the wheel slip event is taking place. Once the wheel slip event is no longer detected, the TCS Active lamp will stop blinking.

The TCS Active indicator will illuminate when the EBCM detects a traction control event. The EBCM supplies a ground signal to the instrument panel (I/P) cluster to illuminate the TCS Active lamp.