Circuit/System Testing

Dimmer Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Ignition ON, verify that a test lamp illuminates between the 12 V reference circuit terminal 1 and ground.
   • If the test lamp does not illuminate, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal and the circuit fuse is open, test the signal circuit terminal 12 for a short to ground.
3. Verify the scan tool LED Backlight Dimming Command parameter is Inactive.
   • If not the specified value, test the signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 BCM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the 12 V reference circuit terminal 1. Verify the scan tool LED Backlight Dimming Command parameter is Active.
   • If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the S30 headlamp switch.

Interior Backlighting Malfunction

NOTE:
Each back lighted component may need to be disconnected to isolate a short to voltage or short to ground. Use the schematic to identify the following:
• Back lighted components the vehicle is equipped with
• Component locations on the back lighting dimming control circuit
• Each component's control and ground circuit terminals
1. Ignition OFF, disconnect the harness connector at the inoperative backlighting component.
2. Ignition OFF, scan tool disconnected, interior lamps OFF, doors CLOSED, test for less than 5 Ω between the ground circuit and ground.
   • If greater than the specified value, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit and ground.
4. Command the LED Backlight Dimming ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
   • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
   • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, replace the inoperative backlighting component.