GM Service Manual Online
For 1990-2009 cars only

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

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Turn ON the ignition, with the engine OFF.
  2. Turn OFF the windshield wipers.
  3. Turn OFF the twilight sentinel delay.
  4. Turn ON the headlamps.
  5. Turn ON and OFF the headlamp dimmer switch.
  6. Turn OFF the headlamps.
  7. Turn OFF the ignition.

Did the headlamps operate properly?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Turn OFF the headlamps.
  4. With a scan tool observe the Headlamp Switch Input parameter in the dash integration module (DIM) Inputs data list.

Does the scan tool display OFF status?

Go to Step 4

Go to Step 12

4

  1. Verify the windshield wiper switch is in the OFF position.
  2. With the scan tool, observe the Lights On with Wipers parameter in the DIM Inputs data list.

Does the scan tool display OFF status?

Go to Step 5

Go to Step 18

5

With the scan tool, observe the Low Beam Output status in the DIM Outputs data list.

Does the scan tool display OFF status?

Go to Step 6

Go to Step 19

6

Are the high beam headlamps on?

Go to Step 7

Go to Step 8

7

With the scan tool, observe the Flash to Pass Switch status in the DIM Inputs data list.

Does the scan tool display OFF status?

Go to Step 10

Go to Step 13

8

  1. Turn OFF the ignition.
  2. Disconnect the HDLP LO BM relay. Refer to Relay Replacement in Wiring Systems.
  3. Turn ON the ignition, with the engine OFF.

Did the low beam headlamps turn OFF?

Go to Step 9

Go to Step 25

9

  1. Turn OFF the ignition.
  2. Connect a test lamp between the HDLP LO BM relay control side supply voltage circuit and the headlamp low beam relay control circuit.
  3. Turn ON the ignition, with the engine OFF.

Did the test lamp illuminate?

Go to Step 14

Go to Step 22

10

  1. Turn OFF the ignition.
  2. Disconnect the HDLP HI BM relay. Refer to Relay Replacement in Wiring Systems.
  3. Turn ON the ignition, with the engine OFF.

Did the high beam headlamps turn OFF?

Go to Step 11

Go to Step 26

11

  1. Turn OFF the ignition.
  2. Connect a test lamp between the HDLP HI BM relay control side supply voltage circuit and the headlamp high beam relay control circuit.
  3. Turn ON the ignition, with the engine OFF.

Did the test lamp illuminate?

Go to Step 15

Go to Step 23

12

  1. Turn OFF the ignition.
  2. Disconnect the headlamp switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool observe the Headlamp Switch Input parameter in the DIM Inputs data list.

Does the scan tool display the OFF status?

Go to Step 21

Go to Step 17

13

  1. Disconnect the turn signal/multifunction switch.
  2. With a scan tool observe the Flash to Pass Switch Input parameter in the DIM Inputs data list.

Does the scan tool display the OFF status?

Go to Step 20

Go to Step 16

14

Test for a short to ground in the headlamp low beam relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 32

Go to Step 19

15

Test for a short to ground in the headlamp high beam relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 32

Go to Step 19

16

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

Did you find and correct the condition?

Go to Step 32

Go to Step 19

17

Test the headlamp switch headlamps on 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 32

Go to Step 19

18

Test for a short to battery positive voltage in the windshield wiper switch on signal circuit of the DIM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 32

Go to Step 19

19

Test for a short to ground in the headlamp relay control circuit of the DIM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 32

Go to Step 24

20

Inspect for poor connections at the harness connector of the turn sign/multifunction switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 32

Go to Step 28

21

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

Did you find and correct the condition?

Go to Step 32

Go to Step 27

22

Inspect for poor connections at the HDLP LO BM relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 32

Go to Step 29

23

Inspect for poor connections at the HDLP HI BM relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 32

Go to Step 30

24

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

Did you find and correct the condition?

Go to Step 32

Go to Step 31

25

Repair the short to battery positive voltage in the headlamp low beam supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

26

Repair the short to battery positive voltage in the headlamp high beam supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

27

Replace the headlamp switch assembly. Refer to Headlamp Switch Replacement .

Did you complete the replacement?

Go to Step 32

--

28

Replace the turn signal/multifunction switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 32

--

29

Replace the HDLP LO BM relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 32

--

30

Replace the HDLP HI BM relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 32

--

31

Important:: After replacement perform the setup procedure for the DIM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System.

Replace the DIM. Refer to Dash Integration Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 32

--

32

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2