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Chevrolet Silverado / GMC Sierra. Manual - part 2476
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
DTC B2585 00
Park Lamp Control Circuit
Diagnostic Fault Information
Circuit/System Description
Voltage is applied at all times to the park lamp relay from battery voltage. When the headlamp
switch is placed in the PARK position and the body control module (BCM) commands the park
lamps ON, the BCM then applies a ground to the park lamp relay control circuit. This engages
the relay and applies voltage through the park lamp fuses and to all the park, license, and tail
lamps.
Conditions for Running the DTC
The Ignition is ON.
The park lamps must be commanded ON by the BCM.
Conditions for Setting the DTC
The BCM detects a short to voltage on the park lamp relay control circuit.
Action Taken When the DTC Sets
All park, license, and tail lamps are inoperative.
Conditions for Clearing the DTC
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
Park Lamp Relay Control
Circuit
1
2
B2585 00
-
1. Park, License, and Tail Lamps Always On
2. Park, License, and Tail Lamps Inoperative
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The conditions for setting the DTC are no longer present.
A history DTC clears after 100 malfunction-free ignition cycles.
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
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, activate the Parking Lamp output control on the scan tool. The Park Lamp Relay
Command parameter in the data list should display On and the park lamps should illuminate.
Circuit/System Testing
1. Ignition OFF, disconnect the park lamp relay.
2. Connect a test lamp between the relay control circuit terminal 85 and the B+ circuit
terminal 86.
3. Command the parking lamps ON and OFF with a scan tool. The test lamp should turn ON
and OFF when changing between the commanded states.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
If the test lamp is always ON, test the relay control circuit for a short to ground. If the
circuit tests normal, replace the BCM.
If the test lamp is always OFF, test the relay control circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the BCM.
4. If all circuits test normal, test or replace the park lamp relay.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an
Electrical Center)
Control Module References for BCM replacement, setup, and programming
DTC B2600
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
DTC B2600 00
Daytime Running Lamp Control Circuit
Diagnostic Fault Information
Circuit/System Description
The daytime running lamps (DRL) are controlled by the body control module (BCM). The BCM
grounds the DRL relay control circuit in order to energize the DRL relay coil. The DRL relay
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
DRL Relay Control Circuit
1
2
B2600 00
-
1. Daytime Running Lamps (DRL) Always On
2. Daytime Running Lamps (DRL) Inoperative
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
then sends voltage to the dedicated DRL or low beam headlamps.
Conditions for Running the DTCs
The headlamp switch is OFF.
The park brake is unapplied.
The engine is running.
Conditions for Setting the DTC
The DRL relay control circuit is shorted to voltage.
Action Taken When the DTC Sets
The BCM turns off the DRL relay control for the remainder of the ignition cycle.
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present.
A history DTC clears after 100 malfunction-free ignition cycles.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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