The ABS VI Antilock Braking System consists of the following
components:
| • | A conventional hydraulic brake system |
The conventional brake system includes the following components:
| • | Interconnecting hydraulic brake lines |
| • | 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 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 hydraulic check valves |
The ABS brake motor pack consists of the following components:
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 unswitched battery voltage |
The outputs include the following components:
| • | Three bi-directional motor controls |
| • | Two solenoid controls (ABS) |
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 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 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:
Refer to
Power Distribution Schematics
in Wiring Systems.
