GM Service Manual Online
For 1990-2009 cars only

The EBCM/EBTCM performs system self-diagnostics, and can detect and often isolate system malfunctions. When a malfunction is detected the EBCM/EBTCM sets a Diagnostic Trouble Code (DTC). The DTC represents the malfunction, and may turn on the Antilock Indicator, Red BRAKE Warning Indicator, and Traction Control indicators (if equipped), and may disable the ABS/TCS functions as necessary for the duration of the ignition cycle.