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 03: Ambient Light Sensor Circuit Below ThresholdDTC B2645 07: Ambient Light Sensor Circuit Above Threshold
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Ambient Light Sensor Signal | B2645 03 | B2645 07 | B2645 07 | -- |
Ambient Light Sensor Ground | -- | B2645 07 | -- | -- |
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 changes. 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 low beam operation. In daylight conditions, the BCM will command the DRLs ON. In low light conditions, the BCM will command the low beam headlamps ON.
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
B2645 03
The DTC will set when the BCM detects a short to ground in the ambient light sensor signal circuit.
B2645 07
The DTC will set when the BCM detects a short to voltage or an open/high resistance in the ambient light sensor signal circuit.
Action Taken When the DTC Sets
| • | Automatic lamp control (ALC) is inoperative. |
| • | The BCM defaults to low light status and commands the low beam 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.
- Ignition OFF, scan tool OFF, doors CLOSED, test for less than 5 ohms between the appropriate ground circuit terminal listed below 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 appropriate signal circuit listed below and ground. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 volts.
- If all circuits test normal, test or replace the ambient light sensor.
| • | Ground terminal B - with C67 |
| • | Ground terminal C - with CJ2 |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM. |
| • | Signal terminal A - with C67 |
| • | Signal terminal D - with CJ2 |
| ⇒ | 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 |
