Section 15 (Anti-Lock Brake System): Diagnosis: Notes
WARNING: This page is about a different car, the 1997 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
The EBTCM performs system self-diagnostics and can detect and often isolate a system malfunction. When a malfunction is detected, EBTCM sets a DTC and illuminate the ABS/TCS warning light and may also disable the ABS/TCS functions as necessary for the duration of the ignition cycle.
The EBTCM performs an auto test once per ignition cycle when ignition is turned to RUN position. The auto test cycles each solenoid valve and pump motor (and all necessary relays) in order to check the component operation. If an error is detected, the EBTCM will set a DTC. The AUTO TEST may felt or heard while it is in progress.