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Chevrolet Silverado / GMC Sierra. Manual - part 2479
Description and Operation
Interior Lighting Systems Description and Operation
Electrical Information Reference
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, headlamp switch to PARK, vary the interior lamp dimming switch from dim to full
bright. The LED lamps should dim and then become full bright.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the affected component.
2. Connect a test lamp between the listed LED dimming control circuit terminal and ground.
IP multifunction switch terminal 6
4wd mode switch terminal 4
PTO switch terminal 7
3. Command the dimming test high to low with a scan tool. The test lamp should turn from
bright to dim when changing between the commanded states.
If the test lamp is always off, test the control circuit for an open/high resistance or
short to ground. If the circuit tests normal, replace the BCM.
If the test lamp is always bright, test the control circuit for a short to voltage. If the
circuit tests normal, replace the BCM.
4. If all circuits test normal, test or replace the affected component.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Refer to the appropriate replacement procedure for the component causing the condition.
Control Module References for BCM replacement, setup, and programming
DTC B2645
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 Threshold
DTC B2645 07
Ambient Light Sensor Circuit 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 depending on outside lighting conditions. The body
control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The 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. In low light conditions, when the headlamps switch is in AUTO position, the BCM
will command the low beam headlamps ON.
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
Ambient Light Sensor Signal
Circuit
B2645 03
B2645 07
B2645 07
B2645 03 or
B2645 07
Ambient Light Sensor Ground
Circuit
-
B2645 07
-
B2645 03 or
B2645 07
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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 voltage is below 0.196 volt in the ambient light sensor
signal circuit.
B2645 07
The DTC will set when the BCM detects voltage is above 4.9 volts in the ambient light sensor
signal circuit or if the ambient light sensor ground circuit is open.
Action Taken When the DTC Sets
When DTC B2645 03 or B2645 07 is present, the ALC will default to 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
Exterior Lights Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Circuit Testing
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
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, test for less than 1 ohm of resistance between the ground circuit terminal C
and ground.
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 volts.
If less than the specified range, test the signal circuit for a short to ground. If the circuit
tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the signal circuit terminal D and the low reference
circuit terminal C. Verify the scan tool light sensor parameter is less than 1.0 volt.
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, test or replace the ambient light sensor.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Ambient Light Sensor Replacement
Control Module References for BCM replacement, setup, and programming
DTC B2652
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 Descriptor
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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