GM Service Manual Online
For 1990-2009 cars only

Important: The following steps must be completed before using the symptoms tables.

  1. Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information before using the symptom tables in order to verify that all of the following are true:
  2. • There are no DTCs set.
    • The control modules can communicate via the serial data link.
  3. Review the system operation in order to familiarize yourself with the system functions. Refer to the following:
  4. •  Exterior Lighting Systems Description and Operation
    •  Interior Lighting Systems Description and Operation

Visual/Physical Inspection

Several of the symptom procedures ask for a careful visual/physical check. This step is extremely important-it could lead to correcting a problem without further checks and can save valuable time. These checks include the following:

    • Inspect for aftermarket devices which could affect the operation of the Lighting System. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Inspect the easily accessible or visible system components and harness connectors for obvious damage or conditions which could cause the symptom.
    • If only one lamp is inoperative, inspect and repair a poor connection or an open in the power feed or ground circuit before replacing the light bulb. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Intermittent

Faulty electrical connections or wiring may also be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose a symptom that does not set a DTC:

    •  Backup Lamps Always On
    •  Backup Lamps Inoperative
    •  Courtesy Lamps Always On
    •  Courtesy Lamps Inoperative
    •  Daytime Running Lamps (DRL) Indicator Inoperative
    •  Daytime Running Lamps (DRL) Inoperative
    •  Fog Lamp Indicator Inoperative
    •  Fog Lamps Always On
    •  Fog Lamps Inoperative
    •  Hazard Lamps Inoperative
    •  Headlamp Low or High Beams Always On
    •  Headlamps Inoperative - High Beams
    •  Headlamps Inoperative - Low Beams
    •  Low and High Beams Headlamps Inoperative
    •  Headlamps Flash to Pass Inoperative
    •  High Beam Indicator Inoperative
    •  Illuminated Entry Lamps Inoperative
    •  Interior Backlighting Does Not Dim
    •  Interior Backlighting Inoperative
    •  Park Lamps Always On
    •  Park Lamps Inoperative
    •  Reading Lamp Inoperative
    •  Stop Lamps Always On
    •  Stop Lamps Inoperative
    •  Turn Signal Lamps and/or Indicators Always On or Flashing
    •  Turn Signal Lamps and/or Indicators Inoperative