Antilock Brake System Operation

PURPOSE
The ITT Teves Mark IVg Anti-Lock Brake System is designed to prevent wheel lock-up on any road surface when brakes are applied.

OPERATION
It is composed of a complex network of electrical and hydraulic components but should usually function much the same as a standard, non-ABS braking system. The hydraulic circuits to each wheel are diagonally split for safety in the event of pressure loss, and conventional vacuum assist is provided on all models.

The anti-lock brake system operates when brakes are applied while traveling at a speed greater than three to five mph.

NOTE: It is normal for slight wheel lock-up to be noted at the end of an ABS stop. In addition, brake pedal vibration and noises such as ticking, popping and groaning are normal when hard braking causes the system to operate.

The anti-lock brake system is comprised of several interactive components not found on vehicles without ABS. These include a Hydraulic Control Unit (HCU), certain fuses and relays, wheel speed sensors, an ABS warning lamp and the Controller Anti-Lock Brake (CAB). Refer to the detailed descriptions of these components in this section for further information.

CIRCUIT OPERATION
Power for the Anti-Lock Brake System (ABS) is supplied by three fuses. There is a 10 Amp fuse in cavity 10 of the junction block. Power for the fuse is supplied by circuit A6. The A6 circuit is a direct battery feed from the Power Distribution Center (PDC) and protected by a 40 Amp fuse located in cavity 6.

Circuit A22 connects, from the ignition switch., to the ABS control module and the coil side of the ABS main relay.

The second fuse is located in the PDC cavity 7. This fuse powers the contact side of the ABS pump monitor relay on circuit A1O. The fuse is HOT at all times.

The third fuse is also located in the PDC. This fuse is located in cavity 17 and is used to power the contact side of the ABS main relay. This fuse is HOT at all times.

There are two grounding points used for the ABS control module. Both of the grounds are on circuit Z2 from the control module to the right cowl.