Headlamps Inoperative - Low Beams. GMC Truck Yukon Denali 2007

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2007 🢒 Yukon Denali 🢒 Body Systems 🢒 Lighting 🢒 Headlamps Inoperative - Low Beams

Headlamps Inoperative - Low Beams High Intensity Discharge (HID)

Step

Action

Yes

Caution: The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:

•	Never open the high intensity discharge system ballast or the arc tube assembly starter.

•	Never probe between the high intensity discharge system ballast output connector and the arc tube assembly.

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference: Lighting Systems Connector End Views or Data Communication 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 ON position.
Place the dimmer switch in the low beam position.

Do the low beam headlamps operate normally?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

Is only one low beam headlamp inoperative?

Go to Step 4

Go to Step 8

Disconnect the forward lamps harness connector from the inoperative headlamp ballast.
Ensure that the headlamp switch is in the HEAD position.
Ensure that the headlamp dimmer switch is in the LOW BEAM position.
Test the battery positive voltage circuit of the inoperative headlamp before the ballast connector for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 5

Test the headlamp low beam supply voltage circuit of the inoperative headlamp before the ballast connector for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 6

Test the ground circuit of the inoperative headlamp before the ballast connector for high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 7

Install a known good headlamp bulb. Refer to Headlamp Bulb Replacement .

Does the lamp operate properly?

Go to Step 19

Go to Step 12

Place the headlamp switch in the HEAD position.
Place the headlamp dimmer switch in the low beam position.
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 17

Go to Step 9

Disconnect the multifunction switch.
Place the headlamp switch in the HEAD position.

Do the low beam headlamps illuminate?

Go to Step 13

Go to Step 10

Test the headlamp dimmer switch signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 11

Test the headlamp switch flash to pass signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 14

Inspect for poor connections at the harness connector of the ballast. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 15

Inspect for poor connections at the harness connector of the headlamp dimmer switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 18

Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 16

Replace the headlamp ballast. Refer to High Intensity Discharge Headlamp Ballast Replacement .

Did you complete the replacement?

Go to Step 19

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

Did you complete the replacement?

Go to Step 19

Replace the low beam relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 19

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

Did you complete the repair?

Go to Step 19

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3

Headlamps Inoperative - Low Beams Standard

Step	Action	Yes	No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Place the headlamp switch in the ON position. Place the dimmer switch in the low beam position. Do the low beam headlamps operate normally?	Go to Testing for Intermittent Conditions and Poor Connections	Go to Step 3
3	Is only one low beam headlamp inoperative?	Go to Step 4	Go to Step 5
4	Test the headlamp low beam supply voltage and ground circuits for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition?	Go to Step 16	Go to Step 9
5	Place the headlamp switch in the HEAD position. Place the headlamp dimmer switch in the low beam position. 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 14	Go to Step 6
6	Disconnect the multifunction switch. Do the low beam headlamps illuminate?	Go to Step 7	Go to Step 11
7	Test the headlamp dimmer switch signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct a condition?	Go to Step 16	Go to Step 8
8	Test the headlamp switch flash to pass signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct a condition?	Go to Step 16	Go to Step 10
9	Inspect for poor connections at the harness connector of the inoperative bulb. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition?	Go to Step 16	Go to Step 12
10	Inspect for poor connections at the harness connector of the headlamp dimmer switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition?	Go to Step 16	Go to Step 15
11	Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition?	Go to Step 16	Go to Step 13
12	Replace the inoperative bulb. Refer to Headlamp Bulb Replacement. Did you complete the replacement?	Go to Step 16	--
13	Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	Go to Step 16	--
14	Replace the low beam relay. Refer to Relay Replacement. Did you complete the replacement?	Go to Step 16	--
15	Replace the headlamp dimmer switch. Refer to Turn Signal Multifunction Switch Replacement. Did you complete the repair?	Go to Step 16	--
16	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 3