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 Listin Wiring 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. Turn ON the headlamps.
  2. Ensure that the headlamp dimmer switch is in the LOW position.

Do both low beam headlamps illuminate?

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 12

Go to Step 4

4

  1. Disconnect the body control module (BCM) connector C1.
  2. Connect a jumper between the headlamp low beam relay control circuit and ground.

Do the low beam headlamps illuminate?

Go to Step 5

Go to Step 7

5

  1. Reconnect the BCM connector C1.
  2. Disconnect the multifunction switch.
  3. Install a jumper between the headlamp switch headlamps ON signal circuit and ground.

Do the low beam headlamps illuminate?

Go to Step 9

Go to Step 6

6

Test for a poor connection , open or short to battery voltage, in the headlamp switch headlamps ON signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 13

7

  1. Remove the low beam headlamp relay.
  2. Install a fused jumper between the battery positive voltage supply circuit and the switched low beam voltage supply circuit.

Do the low beam headlamps illuminate?

Go to Step 8

Go to Step 11

8

Test for a poor connection, open or a short to battery positive voltage in the 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 19

Go to Step 10

9

Inspect for a poor connection at the harness connector of the headlamp dimmer 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 19

Go to Step 14

10

Inspect for a poor connection at the low beam 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 19

Go to Step 15

11

Inspect for a poor connection at the harness connector of the underhood fuse block. 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 19

Go to Step 17

12

Inspect the inoperative low beam headlamp voltage supply and ground circuit for a high resistance, short to ground, 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 16

13

Test for a short to ground or a short to battery positive voltage in the exterior lamps OFF input circuit. Refer to Circuit Testingand Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 18

14

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

Did you complete the replacement?

Go to Step 19

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15

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

Did you complete the replacement?

Go to Step 19

--

16

Replace the inoperative low beam headlamp. Refer to Headlamp Assembly or Headlamp Bulb Replacement .

Did you complete the replacement?

Go to Step 19

--

17

Replace the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you complete the replacement?

Go to Step 19

--

18

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

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3