For 1990-2009 cars

The ABS VI Antilock Braking System consists of the following components:

• | A conventional hydraulic brake system

• | Antilock components

The conventional brake system includes the following components:

• | A vacuum power booster

• | A master cylinder

• | Front disc brakes

• | Rear drum brakes

• | Interconnecting hydraulic brake lines

• | A low fluid sensor

• | A red BRAKE warning indicator

The ABS VI includes the following components:

• | An ABS brake modulator/brake motor pack assembly

• | An electronic brake control module (EBCM)

• | An electronic brake control relay

• | Four wheel speed sensors

• | The interconnecting wiring

• | An amber ABS warning indicator

### ABS Brake Modulator/Motor Pack Assembly

The ABS Brake Modulator/Motor Pack Assembly controls hydraulic pressure to the following areas:

• | The front calipers

• | The rear wheel cylinders

The ABS Brake Modulator/Motor Pack Assembly controls hydraulic pressure by modulating the hydraulic pressure. This action prevents wheel slip.

The basic ABS brake modulator configuration consists of the following components:

• | The gear subassemblies

• | The ball screws

• | The nuts

• | The pistons

• | The hydraulic check valves

The ABS brake motor pack consists of the following components:

• | Three motors

• | Three drive gears

• | Three ESBs

### Electronic Brake Control Module (EBCM)

Important: There is no serviceable or removable PROM. The EBCM must be replaced as an assembly.

The Electronic Brake Control Module (EBCM) controls the ABS VI. A microprocessor controls the EBCM.

The inputs to the system include the following components:

• | The four wheel speed sensors

• | The brake switch

• | The ignition switch

• | The unswitched battery voltage

The outputs include the following components:

• | Three bi-directional motor controls

• | Warning indicators

• | Two solenoid controls (ABS)

• | A system enable relay

A serial data line is provided for service diagnostic tools and assembly plant testing. The serial data line is located in terminal 9 of the Data Link Connector (DLC).

The EBCM monitors the speed of each wheel.

The EBCM controls the motors and the solenoids in order to reduce brake pressure to a particular wheel when the following conditions exist:

• | The wheel is approaching slip.

• | The brake switch is active.

This cycle will repeat until one of the following conditions exists:

• | The vehicle comes to a stop.

• | The brake releases.

• | The wheel no longer approaches slip.

Refer to Self-Diagnostics for more information.

### Front Wheel Speed Sensors

The front wheel speed sensors are of a variable reluctance type. Each sensor is attached to the knuckle assembly in close proximity to a toothed ring. An AC voltage is generated when the toothed ring passes by the sensor. The magnitude and frequency are proportional to the speed of the wheel and both will increase with increasing speed.

The sensor is not repairable.

The air gap is not adjustable.

### Rear Wheel Speed Sensors

The rear wheel speed sensors operate in the same manner as the front wheel speed sensors. Refer to Front Wheel Speed Sensors.

However, the rear wheel speed sensors and the toothed ring are contained within the dust cap of the integral rear wheel bearing. This allows approved environmental protection and easier assembly.

The sensor and the toothed ring are not repairable.

The air gap cannot be adjusted.

The entire integral bearing and speed sensor unit must be replaced if a rear wheel speed sensor fails.

### Electronic Brake Control Relay

The Electronic Brake Control Relay is a normally-open contact type.

The Electronic Brake Control Relay has special contact material to handle the high currents required for the ABS VI operation.

The relay allows battery voltage and current to be supplied to the EBCM. The EBCM supplies power to the motors and the solenoids.

### Brake Fluid Level Indicator Sensor

Refer to Master Cylinder Description in Hydraulic Brakes.

### Wiring Harness

The wiring harness is the mechanism which electrically connects the EBCM to the following components:

• | The power and the ground

• | The wheel speed sensors

• | The motors

• | The solenoids

• | The fuses

• | The switches

• | The indicators

• | The electronic brake control relay

• | The serial communications port

The wiring harness consists of the following components:

• | The wires that provide electrical interconnection

• | The connectors/terminals that provide an electrical/mechanical interface from each wire to a system component

### Warning Indicators

The Electronic Brake Control Module (EBCM) continuously monitors itself and other ABS components.

If the EBCM detects a problem with the system, the amber ABS warning indicator will light continuously (solid indicator) in order to alert the driver of the problem.

• | The red BRAKE warning indicator

• | The amber ABS warning indicator

The amber ABS warning indicator flashes to warn the driver of an existing ABS malfunction which may have degraded the base brake performance. In this situation, the vehicle must be serviced immediately in order to regain full base and ABS operation.

A solid amber ABS warning indicator indicates that a problem has been detected. The problem is one that affects the operation of the ABS. In this situation, no antilock braking or enhanced traction will be available. Normal (non-antilock) brake performance will still be available.

The ABS VI must be serviced in order to regain ABS braking ability.

The following indicators will illuminate any time when the EBCM suspects that the ABS operation is degraded because of a system malfunction:

The amber ABS warning indicator

The red BRAKE warning indicator illuminates when the following conditions exist:

• | The fluid level in the master cylinder is low.

• | The parking brake switch is closed.

• | The bulb test switch section of the ignition switch is closed.

• | Certain ABS DTCs are set.

| (This is controlled by the EBCM.)

The red BRAKE warning indicator alerts the driver that a base brake problem may exist.

### Fuses

The power distribution system of the vehicle consists of the following components:

• | The Maxifuse

• | The two Minifuses

• | The two standard fuses

• | The ignition switch

Refer to Power Distribution Schematics in Wiring Systems.