Mecatronic III

DESCRIPTION - The anti-lock brake system (ABS):
- is a four-wheel system which prevents wheel lockup by automatically modulating the brake pressure at each wheel independently during an emergency stop.
- enables the driver to maintain steering control and stopping in the shortest possible distance under most conditions.
- During normal braking, the ABS pedal feel will be the same as a conventional brake system.
- During ABS operation, a pulsation can be felt in the brake pedal accompanied with a fall and then a rise in the brake pedal height and a clicking sound.

OPERATION - The 4-wheel anti-lock brake system is optional equipment. The system operates as follows:
- Wheel lockup is prevented during an emergency stop by modulating brake pressure.
- Permits the driver to maintain steering control and stop the vehicle in the shortest possible distance under most conditions.
- The pedal effort and pedal feel during normal braking are similar to that of a conventional power-brake system.
- During the anti-lock brake operation, the driver will sense a pulsation in the brake pedal and a clicking sound.

COMPONENTS - The ABS has the following components;
- Power brake booster and brake master cylinder assembly.
- Brake pressure control valve.
- Hydraulic control unit (HCU), which includes a relay box and anti-lock brake control module.
- Front brake anti-lock sensor and rear brake anti-lock sensor.

POWER BRAKE BOOSTER - The diaphragm-type power brake booster:
- Is self-contained.
- Is mounted on the engine side of the cowl.
- Refer to Hydraulic System for brake booster information. Power Brake Assist

BRAKE MASTER CYLINDER
- The brake master cylinder is a tandem master cylinder.
- The ABS brake master cylinder uses only two outlet ports to supply the hydraulic control unit.
- The brake master cylinder has a plastic brake master cylinder reservoir with an integral fluid level switch.
- Refer to Hydraulic System for brake master cylinder information. Brake Master Cylinder

BRAKE PRESSURE CONTROL VALVE
- The brake pressure control valve controls the hydraulic pressure to the rear brakes to maintain a balance between the front and rear circuits.
- The brake pressure control valves are located on the hydraulic control unit.
- Each rear wheel brake has its own brake pressure control valve.
- Refer to Hydraulic System for brake pressure control valve information. Brake Proportioning/Combination Valve

HYDRAULIC CONTROL UNIT (HCU) - The hydraulic control unit is located below the brake master cylinder. The HCU consists of:
- Electronic control unit with relays.
- A four-solenoid valve body.
- Pump motor assembly.

CONTROL MODULE, ANTI-LOCK BRAKE
- The anti-lock brake control module is located on the hydraulic control unit (HCU).
- The HCU monitors and controls ABS operation.
- If a fault occurs in the ABS system a diagnostic trouble code (DTC) will be stored in memory.

BRAKE SENSOR, ANTI-LOCK
- The anti-lock brake sensor electrically senses each tooth of the anti-lock sensor indicator as it passes through the anti-lock brake sensor's magnetic field.
- This data is sent to the anti-lock brake control module. The anti-lock brake control module monitors the brake anti-lock sensors to determine wheel rotational speed.