GM Service Manual Online
For 1990-2009 cars only

The EBTCM performs system self-diagnostics, and can detect and often isolate system malfunctions. When a malfunction is detected the EBTCM sets a Diagnostic Trouble Code (DTC). The DTC represents the malfunction, turns ON the Antilock and/or Traction Control indicators (in almost all instances), and may disable the ABS/TCS functions as necessary for the duration of the ignition cycle.