B2645
DTC B2645
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC B2645 03
-
Ambient Light Sensor Circuit Voltage Below Threshold
DTC B2645 07
-
Ambient Light Sensor Circuit Voltage Above Threshold
Diagnostic Fault Information
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 0.2 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a 5 V reference signal to the ambient light sensor. The body control module (BCM) monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the DRLs ON by applying ground to the DRL relay via the DRL relay control circuit. When the BCM applies ground to the DRL relay control circuit, the DRL relay coil energizes causing the relay switch contacts to close. With the DRL relay switch contacts closed, battery voltage flows through the DRL 1 and DRL 2 fuses to the left and right LO HDLP fuses to the low beam headlamps. The DRL control circuit that supplies the low beam headlamp fuses with voltage contains a loop of wire that acts as resistance. This resistance is responsible for the low beam headlamps illuminating at a reduced intensity. Any function or condition that turns on the headlamps will cancel DRL operation.
Conditions for Running the DTC
Battery voltage must be between 9-16 V.
Conditions for Setting the DTC
B2645 03
The BCM detects a short to ground in the ambient light sensor signal circuit.
B2645 07
The BCM detects a short to voltage or an open/high resistance in the ambient light sensor signal circuit.
Actions 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
Headlights/Daytime Running Lights (DRL) Schematics Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
Exterior Lighting Systems Description and Operation Exterior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
2. Ignition OFF, scan tool OFF, doors CLOSED, test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground.
* Terminal B - (C67/C42)
* Terminal C - (CJ2)
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.5 V.
• If less than the specified range, test the signal circuit terminal listed below for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
* Terminal A - (C67/C42)
* Terminal D - (CJ2)
4. Install a 3 A fused jumper wire between the signal circuit terminal listed below and ground. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V.
* Terminal A - (C67/C42)
* Terminal D - (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
5. If all circuits test normal, replace the ambient light sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Ambient Light Sensor Replacement Service and Repair
* Control Module References Control Module References for BCM replacement, setup, and programming