GM Service Manual Online
For 1990-2009 cars only
  1. Inspect the PNL and Tail MKR Circuit Breakers to determine if they are open. If they are open, Locate and Repair the cause of the circuit overload and then Replace the circuit breaker.
  2. Inspect ground G 102 to assure that it is clean and tight.
  3. Inspect the lamps for an open or shorted filament. Replace the lamps if necessary.
  4. Inspect the wiring for broken or partially broken conductors inside the insulation which could cause system malfunction but prove to be GOOD in a continuity or voltage test with the system disconnected. These circuits maybe intermittent or resistive when in use. The circuit should be monitored for a voltage drop during operation.
  5. Inspect for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer to Checking Aftermarket Accessories ).