For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Headlights Schematics Connector End View Reference: Master Electrical Component List
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Are both low beam headlamps inoperative? | Go to Step 3 | Go to Step 8
3 |

1. Install the scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Turn ON the headlamps.
4. With the scan tool, observe the Headlamp Switch parameter in the instrument panel module (IPM) Inputs data list.

Does the data parameter display ON?

Go to Step 5

Go to Step 4

4 |

1. Turn OFF the ignition.
2. Disconnect the turn signal/multifunction switch C3 harness connector.
3. Connect a 3-amp fused jumper between the headlamp ON signal circuit and the ground circuit of the turn signal/multifunction switch at the C3 harness connector.
4. Turn ON the ignition, with the engine OFF.
5. With a scan tool, observe the Headlamp Switch parameter in the instrument panel module (IPM) inputs data list.

Does the Headlamp Switch parameter display ON?

Go to Step 14

Go to Step 11

5 |

1. Turn OFF the ignition.
2. Disconnect the headlamp LOW BEAM relay located in the underhood fuse block. Refer to Relay Replacement .
3. Connect a test lamp between the headlamp low beam relay control side supply voltage circuit and the headlamp low beam relay control circuit.
4. Turn ON the ignition, with the engine OFF.
5. Turn ON the low beam headlamps.

Does the test lamp illuminate?

Go to Step 6

Go to Step 10

6 | Connect a test lamp between the headlamp low beam relay switch side supply voltage circuit and ground. Does the test lamp illuminate? | Go to Step 7 | Go to Step 19
7 |

1. Turn OFF the ignition.
2. Connect a 40-amp fused jumper between the headlamp low beam relay switch side supply voltage circuit and the headlamp low beam supply voltage circuit.
3. Turn ON the ignition, with the engine OFF.

Do both of the low beam headlamps illuminate?

Go to Step 15

Go to Step 8

8 |

1. Disconnect the inoperative low beam headlamp.
2. Connect a test lamp between the low beam headlamp supply voltage circuit at the inoperative low beam headlamp and the ground circuit of the inoperative low beam headlamp.

Does the test lamp illuminate?

Go to Step 17

Go to Step 9

9 | Test the headlamp low beam supply voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 18
10 | Test the headlamp low beam relay control circuit for an open, high resistance, or short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 13
11 | Test the turn signal/multifunction switch ground circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 12
12 | Test the turn signal/multifunction switch headlamp ON signal circuit for an open, high resistance, or short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 13
13 | Test the twilight sentinel delay signal circuit of the IPM for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 16
14 | Inspect for poor connections at the C3 harness connector of the turn signal/multifunction switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 20
15 | Inspect for poor connections at the headlamp low beam relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 21
16 | Inspect for poor connections at the harness connector of the IPM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 22
17 | Inspect for poor connections at the harness connector of the inoperative low beam high intensity discharge (HID) headlamp. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 25 | Go to Step 23
18 | Locate and repair an open or high resistance in the headlamp ground circuit. Refer to Circuit Testing and Wiring Repairs . Did you complete the repair? | Go to Step 25 | --
19 | Locate and repair an open or high resistance in the switch side supply voltage circuit of the headlamp low beam relay. Refer to Circuit Testing and Wiring Repairs . Did you complete the repair? | Go to Step 25 | --
20 | Replace the turn signal/multifunction switch. Refer to Turn Signal Multifunction Switch Replacement . Did you complete the replacement? | Go to Step 25 | --
21 | Replace the headlamp low beam relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 25 | --
22 | Replace the IPM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 25 | --
23 | Replace the inoperative HID headlamp arc tube. Refer to Front Side Marker Lamp Bulb Replacement . Do the low beam headlamps operate properly? | Go to Step 25 | Go to Step 24
24 | Replace the inoperative HID headlamp ballast. Refer to Front Side Marker Lamp Bulb Replacement . Did you complete the replacement? | Go to Step 25 | --
25 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2