Test Description

The Electronic Brake Control Module (EBCM) monitors its own performance and certain input and output signals to determine if a system malfunction has occurred. Most ABS self-diagnostics are performed by the controller after the vehicle reaches 1.7 mph. For this reason, the vehicle must be road tested to check for malfunctions that will set fault codes.
The Built-In Test Equipment (BITE) test is performed once during each ignition cycle when the vehicle reaches 3-11 mph. The BITE test cycles each solenoid valve and the pump motor to test component operation. The EBCM also checks its own logic section and circuitry. If faults are detected during this test, the EBCM will set a code. The BITE test occurs once each ignition cycle as follows:
1. After receiving an Ignition On input, the EBCM grounds and activates the solenoid relay.
2. When the vehicle reaches 3-11 mph, the EBCM tests the solenoid valves and pump in the hydraulic modulator.
3. If the pump or solenoid valves fail to operate, the ABS will be disabled, a fault code will set and the SERVICE ABS indicator will illuminate.
4. When the EBCM receives a signal from any of the wheel speed sensors, it checks wheel speed sensor output. If any wheel speed sensor signal is missing, the ABS will be disabled, a fault code will set and the SERVICE ABS indicator will illuminate.

Once the vehicle is moving, the EBCM continuously monitors itself and the following components:
1. Modulator valves.
2. Wheel speed sensors.
3. Wiring harness and relays.
4. Battery voltage.

If battery voltage drops below approximately 9 volts, the ABS is disabled and the SERVICE ABS indicator will illuminate.
Each malfunction has an associated fault code, which is a two-digit number flashed over the SERVICE ABS lamp in the Driver Information Center (DIC). The system can store up to three fault code at once (in addition to Code 12). These codes may be either three separate fault codes, or three of the same codes if an intermittent condition occurs three times.
Some fault codes involving the solenoid valves and pump motor prevent the SERVICE ABS lamp from flashing. If one of these codes is present, the SERVICE ABS lamp will remain On and the system will be unable to enter the diagnostic display (flash codes) mode. In this case, the Tech 1 Diagnostic Computer tool No. 94-00101-A or equivalent must be used.