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

• | A proportioning valve

• | 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/motor pack assembly

• | An electronic brake control module (EBCM)

• | An electronic brake control relay

• | Four wheel speed sensors

• | The interconnecting wiring

• | A lamp driver relay

• | An amber ABS warning indicator

• | A blue ABS ACTIVE 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

Refer to Base Brake System and Antilock Brake System in this section for more information.

### Electronic Brake Control Module (EBCM)

Notice: There is no serviceable or removable PROM. The EBCM/EBTCM 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

• | An electronic brake control relay

• | A lamp driver relay

A serial data line is provided for service diagnostic tools and assembly plant testing.

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.

When the wheel regains traction, brake pressure increases until the wheel approaches slip again.

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 and Rings

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. The toothed ring is pressed onto the outer Constant Velocity (CV) joint. 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 and Rings

The rear wheel speed sensors operate in the same manner as the front wheel speed sensors.

The rear wheel speed sensors are mounted in the rear suspension knuckles. The rear wheel speed sensor reluctor ring is part of the rear hub and bearing 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 and solenoids. The EBCM supplies power to the motors.

### 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 lamp driver 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

### Wheel Speed Sensor Jumper Harness

A jumper harness located between each wheel speed sensor and the main wiring harness.

Each jumper harness is made of highly flexible twisted pair wiring.

The wiring exists because the main harness must connect to the suspension of the vehicle. Therefore, the wiring in this area is subjected to the same motion as a spring or a shock absorber. Any repair to this section of wiring will result in stiffening. Stiffening will eventually result in failure due to wire fatigue.

The wheel speed sensor jumper harnesses are not repairable and must be replaced. Do not attempt to solder, splice, or crimp the harnesses. Eventual failure will occur.

Refer to Wheel Speed Sensor Jumper Harness Replacement (Front) and Wheel Speed Sensor Jumper Harness Replacement (Rear) .

### 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 amber ABS warning indicator

• | The blue ABS ACTIVE indicator

• | The red BRAKE 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 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.

#### ABS Active Indicator

Since brake pedal feedback normally associated with ABS operation does not occur with ABS-VI, there is an additional indicator in the instrument cluster to inform the driver of ABS operation. The blue ABS ACTIVE indicator will illuminate during an ABS event and during system initialization.

#### Brake 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 ignition switch is in START or under control of the EBCM.

The EBCM will illuminate the red BRAKE warning indicator when an ABS fault could interfere with base brake operation.

When this type of fault is detected, the EBCM will store the appropriate DTC and disable ABS.

### Fuses

The power distribution system of the vehicle consists of the fuses and the ignition switch. The fuses are as follows:

• | The Hazard Fuse

• | The Stop Fuse

• | The IG Coil Fuse

• | The DEF Fuse

• | The ABS Fuse