Circuit Description
The body control module (BCM) monitors the ambient light sensor signal circuit in order to determine if the daytime running lights (DRL) or the auto headlights (ALC) should be turned ON in the AUTO mode. When the BCM senses the ambient light sensor voltage is between 1.75-4.9 volts, either the DRL will be commanded ON or the ALC will be commanded ON.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2645 Ambient Light Circuit
Conditions for Running the DTC
The system voltage must be between 9.0-16.0 volts.
Conditions for Setting the DTC
| • | When the ambient light sensor signal voltage is less than 1.75 volts. |
| • | When the ambient light sensor signal voltage is more than 4.9 volts. |
Action Taken When the DTC Sets
The ALC will remain ON in any ambient light state.
Conditions for Clearing the MIL/DTC
| • | This DTC will clear immediately after the condition for setting the fault is corrected. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | Use a scan tool in order to clear history and current DTCs. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Lighting Systems Connector End Views or Lighting Systems Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that the Ambient Light Sensor parameter is within the specified range? | 1.75-4.9 V | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Does the scan tool indicate that the ambient light sensor parameter is less than the specified value? | 0.02 V | Go to Step 4 | Go to Step 5 |
4 | Test the ambient light sensor circuit of the ambient light sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 |
5 | Test the ambient light sensor signal circuit of the ambient light sensor for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the ambient light sensor. 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 |
7 | Inspect for poor connections at the harness connector of the 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 |
8 | Replace the ambient light sensor. Refer to Ambient Air Temperature Gage Sensor 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 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
