Circuit Description
The ambient light sensor indicates the light level to control the automatic headlamps and park lamps. The body control module (BCM) provides a 5 volt reference signal to the ambient light sensor through the ambient light sensor signal circuit. The BCM receives the modified voltage from the ambient light sensor through the ambient light sensor low reference circuit. A low voltage under 1.5V, signals a dark condition to the BCM and vice versa.
Conditions for Running the DTC
The ignition switch is in the on position.
Conditions for Setting the DTC
Any of the following conditions will set this DTC:
| • | The ambient light sensor signal reference circuit is shorted to battery for 5 seconds. |
| • | The ambient light sensor signal reference circuit is shorted to battery for 5 seconds. |
Action Taken When the DTC Sets
| • | The ALC headlamp and park lamp relay control are disabled for the remainder of the ignition cycle. |
| • | The SERVICE indicator illuminates. |
| • | The check gauges chime sounds. |
Conditions for Clearing the DTC
| • | The conditions for setting the DTC are no longer present. |
| • | A history DTC clears after 100 malfunction free ignition cycles. |
| • | The BCM receives the clear code command from the scan tool. |
Diagnostic Aids
If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics | ||||
1 | Did you perform the Lighting System Diagnostic System Check? | -- | Go to Step 2 | |
Does the scan tool indicate that the PHOTOCELL VOLTAGE parameter is within the specified range? | 0.5-4.5 volts | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
3 | Test the low reference circuit of the ambient light sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 4 |
4 | 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 in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 5 |
5 |
Important: Perform the set up procedure for the body control module. Replace the body control module. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | -- | Go to Step 6 | -- |
6 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
