Schematic Reference: Exterior Lights Schematics .

Connector End View Reference: Component Connector End Views .

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle .

Place the headlamp switch in the OFF position.

Do the high and low beam headlamps operate normally?

Go to Testing for Intermittent Conditions and Poor Connections .

Go to Step 3

Are only the high beam headlamps always ON?

Go to Step 4

Go to Step 8

Disconnect the headlamp dimmer switch.

Do the high beam headlamps remain ON?

Go to Step 5

Go to Step 10

Test the following circuits for a short to ground as applicable. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct a condition?

System OK

Go to Step 6

Remove the LT HI BEAM and RT HIGH BEAM fuses from the underhood body electrical centre (UBEC).

Do the high beam headlamps remain ON?

Repair the short to voltage in the right or left high beam headlamp supply voltage circuit. Refer to Wiring Repairs .

Go to Step 7

With a scan tool, monitor the High Beam Relay Command data parameter in the body control module (BCM) data list.

Does the scan tool display On?

Go to Step 11

Replace the UBEC. Refer to Underhood Electrical Center or Junction Block Replacement .

Remove the LT LO BEAM and RT LO BEAM fuses from the UBEC.

Do the low beam headlamps remain always ON?

Repair the short to voltage in the right or left low beam headlamp supply voltage circuit. Refer to Wiring Repairs .

Go to Step 9

With a scan tool, monitor the Low Beam Relay Command data parameter in the body control module (BCM) data list.

Does the scan tool display On?

Go to Step 11

Replace the UBEC. Refer to Underhood Electrical Center or Junction Block Replacement .

Inspect for poor connections at the harness connector of the headlamp dimmer switch. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

System OK

Replace the headlamp dimmer switch. Refer to Turn Signal Switch Replacement .

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

System OK

Replace the BCM. Refer to Control Module References , for replacement, setup, and programming.