Antilock General Description

Functional Diagram:

The Antilock Brake System (ABS) is designed to prevent wheel lockup under heavy braking conditions on virtually any type of road surface. Antilock braking is desirable because a vehicle which stops without the wheels locking, normally stops in a shorter distance than a vehicle with locked wheels. Also, a vehicle which stops without the wheels skidding retains directional stability and some steering control. This allows the driver to retain greater vehicle control during heavy braking.

In addition to antilock brakes, some vehicles may also be equipped with a Traction Control System (TCS). Traction control prevents the drive wheels from spinning excessively during acceleration. The system, designed to operate at all vehicle speeds, reduces wheel slip by braking the wheel that is losing traction, while simultaneously reducing engine power through fuel cut off and spark retard.

DEFINITIONS/ABBREVIATIONS
Several abbreviations that are commonly used throughout are presented here for reference.

ABS Antilock Brake System
CKT Circuit
DLC Data Link Connector
DTC Diagnostic Trouble Code
DVOM Digital Volt-Ohm Meter
EBCM Electronic Brake Control Module
EBTCM Electronic Brake and Traction Control Module
kPa kilo Pascals (pressure)
mV Millivolts
PMV Pressure Modulator Valve
PSI Pounds/Square Inch (pressure)
TCS Traction Control System
VDC DC Volts
VAC AC Volts
WSS Wheel Speed Sensor

BASIC KNOWLEDGE REQUIRED
Basic Electrical Circuits
You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram.

Use Of Circuit Testing Tools
You should know how to use a test lamp and how to use jumper wires to bypass components to test circuits. You should be familiar with the High Impedance Multimeter Digital Volt-Ohm Meter (DVOM) J 34029-A or equivalent. You should be able to measure voltage, resistance and current, and be familiar with the meter controls and how to use them correctly.

Sources Of Additional Information
When you need a review of basic electrical troubleshooting, refer to "Repair Procedures" found in General Information for helpful information. Basic use of circuit testing tools is also covered. Diagnostic Aids