Power-Up Self-Test

The electronic brake control module (EBCM) is able to detect many malfunctions whenever the ignition is ON. However, certain failures cannot be detected unless active diagnostic tests are performed on the components. Shorted solenoid coil or motor windings, for example, cannot be detected until the components are commanded ON by the EBCM. Therefore, a power-up self-test is performed to verify correct operation of system components. The EBCM performs the first phase of the power-up self-test when the ignition is first turned ON. This phase consists of internal self-testing of the EBCM along with electrical checks of system sensors and circuits.

The second phase of the power-up self-test begins when the vehicle is driven at a speed greater than 15 km/h (9 MPH) and the EBCM has not detected any traction control/vehicle stability related concerns. This phase of the power-up self-test may be heard or felt by the driver. The system solenoids and ABS pump motor are commanded ON and OFF to verify the proper operation and the EBCM verifies the ability to return the system to base braking in the event of a failure. The EBCM isolates all of the wheels by briefly closing the four isolation valves, and occasionally the driver may detect this by experiencing a momentary hard pedal.