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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 Yukon XL Denali 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Headlamps Inoperative - Low Beams

Headlamps Inoperative - Low Beams High Intensity Discharge (HID)

Step

Action

Yes

No

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 Computer/Integrating Systems Connector End Views in Computer/Integrating Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Place the headlamp switch in the ON position.
  2. 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 in Wiring Systems

Go to Step 3

3

Is only one low beam headlamp inoperative?

Go to Step 4

Go to Step 8

4
  1. Disconnect the forward lamps harness connector from the inoperative headlamp ballast.
  2. Ensure that the headlamp switch is in the HEAD position.
  3. Ensure that the headlamp dimmer switch is in the LOW BEAM position.
  4. 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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 5

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 6

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 7

7

Install a known good headlamp blub. Refer to Headlamp Assembly or Headlamp Bulb Replacement .

Does the lamp operate properly?

Go to Step 19

Go to Step 12

8
  1. Disconnect the headlamp low relay.
  2. Connect a test lamp between the control circuit of the headlamp low relay and the battery positive voltage circuit of the headlamp low relay connector.

Does the test lamp illuminate?

Go to Step 17

Go to Step 9

9
  1. Connect the headlamp low relay.
  2. Disconnect the multifunction switch.
  3. Place the headlamp switch in the HEAD position.

Do the low beam headlamps illuminate?

Go to Step 13

Go to Step 10

10

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

Did you find and correct the condition?

Go to Step 19

Go to Step 11

11

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

Did you find and correct the condition?

Go to Step 19

Go to Step 14

12

Inspect for poor connections at the harness connector of the ballast. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 15

13

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

Did you find and correct the condition?

Go to Step 19

Go to Step 18

14

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

Did you find and correct the condition?

Go to Step 19

Go to Step 16

15

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

Did you complete the replacement?

Go to Step 19

--

16

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 19

--

17

Replace the low beam headlamp relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 19

--

18

Replace the headlamp dimmer switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the repair?

Go to Step 19

--

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 Computer/Integrating Systems Connector End Views

1

Did you perform the Lighting Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Place the headlamp switch in the ON position.
  2. 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
  1. Disconnect the headlamp low relay.
  2. Connect a test lamp between the control circuit of the headlamp low relay and the battery positive voltage circuit of the headlamp low relay connector.

Does the test lamp illuminate?

Go to Step 14

Go to Step 6

6
  1. Connect the headlamp low relay.
  2. Disconnect the multifunction switch.
  3. Place the headlamp switch in the HEAD position.

Do the low beam headlamps illuminate?

Go to Step 10

Go to Step 7

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 11

9

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

Did you find and correct the condition?

Go to Step 16

Go to Step 13

12

Replace the inoperative bulb. Refer to Headlamp Assembly or 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 headlamp 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