GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

  1. Install the scan tool.
  2. Turn the ignition switch to the ON position.
  3. Select BCM DTC with the scan tool.
  4. Check for any stored DTCs which may have an effect on serial data line communication.
  5. Turn ignition switch OFF.
  6. Remove the scan tool.

No DTCs are stored in memory.

DTC is stored in memory. Go to applicable DTC table.

2

  1. Turn the ignition switch to the ON position.
  2. Turn the I/P dimmer switch to the HIGH position.
  3. Turn the headlamp switch to the PARK position.

The following illumination lamps turn on inside the passenger compartment:

    • Radio faceplate.
    • Instrument cluster.
    • HVAC control head faceplate.
    • Fog lamp switch.
    • MEMORY, MIRRORS, DOORLOCK, and WINDOW switch faceplate.
    • Inside rearview mirror LED.
    • Fog Lamp Switch Illumination is Inoperative.
    • Lamp Inoperative-One Instrument Panel (Illumination Always On).
    • Lamp Inoperative-One Instrument Panel (HVAC Illumination Inop).
    • Lamp Inoperative-One Instrument Panel (TCS Illumination Inop).

3

  1. Turn the I/P dimmer switch slowly to the LOW position.
  2. Return the I/P dimmer switch to the HIGH position.
  1. The brightness of the I/P, radio, HVAC and door lamps slowly decrease.
  2. The brightness of the I/P, radio, HVAC and door lamps slowly increase.

Lamps Erratic with Dimmer Switch-Incandescent.

4

Turn the headlamp switch to the OFF position.

The I/P lamps, HVAC, and radio illumination lamps turn OFF.

    • Lamps Inoperative-One Instrument Panel (HVAC Illumination Always ON).
    • Lamps Inoperative-One Instrument Panel (Illumination Always On).

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.