Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Ambient Light Sensor Signal | B2645 02 | B2645 05 | B2645 05 | -- |
Headlamp - Low Beam Control - Right | 2 | 2 | 2 | -- |
Headlamp - Low Beam Control - Left | 2 | 2 | 2 | -- |
Ambient Light Sensor Low Reference | -- | 1 | 1 | -- |
Headlamp - Low Beam Ground - Right | -- | 2 | -- | -- |
Headlamp - Low Beam ground - Left | -- | 2 | -- | -- |
1. Daytime Running Lamps Malfunction 2. Headlamps Malfunction | ||||
Circuit/System Description
The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 2-4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a low reference ground and a 5-volt reference signal to the ambient light sensor. The BCM monitors the daytime running lamps (DRL) ambient light sensor signal circuit to determine if outside lighting conditions are correct for either DRL or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In high outside light conditions the BCM will command the DRLs ON. In low light conditions, when the headlamps switch is in AUTO position, the BCM will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel the DRL operation.
Diagnostic Aids
Important: This diagnostic procedure assumes that the low beam headlamps are operating within specifications. If the low beam headlamps are inoperative, diagnose the low beam headlamp malfunction before proceeding with the following diagnostic. Refer to Headlamps Malfunction.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ambient light sensor.
- Ignition OFF, scan tool OFF, doors CLOSED, test for less than 20 ohms between the low reference circuit terminal B and ground.
- Ignition ON, verify the scan tool Ambient Light Sensor parameter is between 1-5 volts.
- If all circuits test normal, replace the ambient light sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than the specified range, test the signal circuit terminal A for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
