DAR Pre-Arming

The DAR pre-arming function operates when the transfer box is in high range to reduce the parking brake release time during DAR and to provide a smooth take-off. DAR pre-arming is invoked when:

• The ignition is ON.
• The transmission is in gear 1, 2 or R.
• The vehicle is stationary.
• No failsafe tighten actuation has occurred.

AUTOMATIC LOAD ADJUSTMENT

While the ignition is on, the EPBCM constantly monitors the input from the force sensor. If the tension of the brake cables goes outside the limits for a given operating mode, the EPBCM automatically restores the tension within limits.

Failsafe Tighten.  If, during pre-arming, the vehicle moves, then the maximum cable force is reinstated for the remainder of that ignition cycle.

Automatic Apply.  While the parking brake is applied, if the tension of the brake cables decreases by a prescribed amount from the initial setting, the EPBCM automatically restores the tension to the initial setting.

Automatic Release.  While the parking brake is released, if the tension of the brake cables increase to a prescribed amount, the EPBCM automatically reduces the tension to zero.

ELECTRIC PARK BRAKE (EPB) SWITCH MONITORING

The EPBCM monitors for the following types of fault in the EPB switch system. If a fault is detected, the EPBCM stores a related fault code:

• Short circuits between a pull-down transistor in the EPBCM and battery voltage.
• Broken wires and microswitches.
• Plausibility.

The EPB switch has a degree of in-built redundancy. If a single microswitch fault is detected the EPBCM can still determine the operating state of the EPB switch. Short circuits or multiple failures cause the EPBCM to disable the EPB switch for the remainder of the ignition cycle. The EPBCM also disables the EPB switch if a plausibility fault occurs. However, since plausibility faults are usually caused by incomplete operation of the EPB switch, the EPB switch is re-enabled if the EPBCM subsequently establishes a plausible operating state.

If a single microswitch fault is detected, the EPBCM signals the IC to illuminate the amber parking brake warning indicator. On vehicles with the high line IC, the EPBCM also signals the IC to display a message advising there is a parking brake fault. During an apply actuation, the EPBCM also signals the IC to flash the red parking brake warning indicator.

For all other fault types, the EPBCM signals the IC to illuminate the amber parking brake warning indicator, and, on vehicles with the high line IC, to display a message advising the parking brake has a fault and is not functioning. If it makes an apply actuation, the EPBCM signals the IC to flash the red parking brake warning indicator for the remainder of the ignition cycle.

On the next ignition cycle, the warning indicators and the messages are only activated if the fault is still present, although the fault code is retained by the EPBCM until cleared by T4.