GM Bonneville/Eighty Eight/LeSabre 1986-1999

General Information

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See Figure 1

The Delco VI Anti-lock Braking System (ABS) was first introduced on these vehicles in 1994. In 1996, the standard ABS system was the Delco Bosch V system. ABS provides the driver with 3 important benefits over standard braking systems: increased vehicle stability, improved vehicle steerability, and potentially reduced stopping distances during braking. It should be noted that although the ABS-VI system offers definite advantages, the system cannot increase brake pressure above master cylinder pressure applied by the driver and cannot apply the brakes itself.

Vehicles with the Traction Control System (TCS), utilize a Electronic Brake and Traction Control Module (EBTCM).

These Anti-lock Braking Systems consist of a conventional braking system with vacuum power booster, compact master cylinder, front disc brakes, rear drum brakes and interconnecting hydraulic brake lines augmented with the ABS components. The ABS-VI system includes a pressure modulator valve, Electronic Brake Control Module (EBCM or EBTCM), a system relay, 4 wheel speed sensors, interconnecting wiring and an amber ABS warning light.

The EBCM monitors inputs from the individual wheel speed sensors and determines when a wheel or wheels is/are about to lock up. The EBCM controls the motors on the hydraulic modulator assembly to reduce brake pressure to the wheel about to lock up. When the wheel regains traction, the brake pressure is increased until the wheel again approaches lock-up. The cycle repeats until either the vehicle comes to a stop, the brake pedal is released, or no wheels are about to lock up. The EBCM also has the ability to monitor itself and can store diagnostic codes in a non-volatile (will not be erased if the battery is disconnected) memory. The EBCM is serviced as an assembly.



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Fig. Fig. 1: Typical ABS system components - 1996-99 vehicles with TCS shown, others similar

The Anti-lock braking system employs 2 modes: base (conventional) braking and anti-lock braking. Under normal braking, the conventional part of the system stops the vehicle. When in the ABS mode, the Electromagnetic Brakes (EMB) action of the ABS system controls the two front wheels individually and the rear wheels together. If the one rear wheel is about to lock up, the hydraulic pressure to both wheels is reduced, controlling both wheels together.

BASIC KNOWLEDGE REQUIRED



Before using this section, it is important that you have a basic knowledge of the following items. Without this basic knowledge, it will be difficult to use the diagnostic procedures contained in this section.

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 shorted wire. You should be able to read and understand a wiring diagram.

Use Of Circuit TES