The Delco® Anti-lock Braking System (ABS) VI was first introduced on W-body cars in 1992. 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.
The ABS-VI Anti-lock Braking System consists of a conventional braking system with vacuum power booster, compact master cylinder, front disc brakes, rear disc or drum brakes and interconnecting hydraulic brake lines augmented with the ABS components. The ABS-VI system includes a hydraulic modulator assembly, Electronic Brake Control Module (EBCM), 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 is 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.
The ABS-VI 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.
An Enhanced Traction System (ETS) is used on some W-Body vehicles. The Antilock Brake System and the Enhanced Traction System (ABS/ETS) are both part of the same hydraulic and electric system. Both systems use many of the same components and a problem in either system may disable the other system until it is repaired. Anti-lock braking controls wheel slip when braking. The ETS system provides the capability to control wheel spin at the drive wheels. This improves the ability to maintain vehicle stability and acceleration (drive traction) under changing road and vehicle load conditions.
The Variable Effort Steering (VES) control logic is integrated in the Electronic Brake Control Module/Electronic Brake Traction Control Module (EBCM/EBTCM ). Two Diagnostic Trouble Codes (DTCs) are stored in the EBCM/EBTCM for VES malfunctions. The VES and the ABS share the same wheel speed sensors.
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 Testing Tools -You should know how to use a test light and how to use jumper wires to bypass components to test circuits. You should be familiar with the High Impedance Multimeter such as J 34029-A. You should be able to measure voltage, resistance and current and be familiar with the meter controls and how to use them correctly.