For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Lighting Systems Connector End Views and 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 |

1. Carefully supply sufficient light to the ambient light sensor.
2. Place the headlamps in the AUTO position.

Does the system operate normally?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3 | Remove the DRL fuse in the underhood fuse block. Do the DRL turn OFF? | Go to Step 4 | Go to Step 7
4 |

1. Reinstall the DRL fuse.
2. Use the scan tool to observe the DRL Status parameter while switching the headlamp switch back and forth several times between AUTO and HEAD.

Does the DRL parameter change states as expected?

Go to Step 5

Go to Step 6

5 | Inspect for poor connections at the harness connector of the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 8
6 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 9
7 | Repair the DRL supply voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 10 | --
8 | Replace the DRL relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 10 | --
9 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 10 | --
10 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3