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. |
DTC Descriptors
DTC B2645: Ambient Light Sensor CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
DRL Ambient Light Sensor Signal | B2645 | B2645 | B2645 | -- |
Ambient Light Sensor Ground | -- | B2645 | B2645 | -- |
Circuit/System Description
The ambient light sensor is used to monitor outside lighting conditions. The body control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The sensor is a variable resistor, it's resistance changes as outside lighting conditions change. With the headlamp switch in the AUTO position, the BCM monitors the sensor signal circuit to determine if the outside lighting conditions are correct for either daytime running lamps (DRL) or headlamp operation. In daylight conditions, the BCM will command the DRLs ON. In low light conditions, the BCM will command the headlamps ON.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The headlamp switch in the AUTO position. |
Conditions for Setting the DTC
The DTC will set when the BCM detects the ambient light sensor signal voltage is below 0.2 volts or above 4.9 volts.
Action Taken When the DTC Sets
The BCM defaults to low light status and commands the headlamps ON.
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
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 (RPO C67) or sunload sensor assembly (RPO CJ2).
- Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal B (C67) or C (CJ2) and ground.
- Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 volts.
- Install a 3A fused jumper wire between the signal circuit terminal A (C67) or D (CJ2) and the low reference circuit terminal ground. Verify the scan tool Ambient Light Sensor parameter is less than 0.2 volts.
- If all circuits test normal, test or replace the ambient light sensor (C67) or sunload sensor assembly (CJ2).
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. |
| ⇒ | If less than the specified range, test the signal circuit terminal A (C67) or D (CJ2) for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than the specified range, test the signal circuit 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 |
