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Chevrolet Silverado / GMC Sierra. Manual - part 2475
The BCM receives a mismatched signal between the headlamp switch headlamps OFF signal
circuit, the headlamps switch headlamps ON signal circuit, and the headlamp switch parklamps
signal circuit.
Action Taken When the DTC Sets
The BCM disregards the headlamp switch input and defaults to automatic headlamp function.
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
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, headlamp switch to PARK, just the park lamps should illuminate. Headlamp switch
to HEAD, the park lamps and headlamps should illuminate.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition ON, verify the scan tool headlamp switch parameter is inactive.
If not the specified value, test the signal circuit terminal 1 for a short to ground. If the
circuit tests normal, replace the BCM.
3. Install a 3A fused jumper wire between the signal circuit terminal 2 and the low reference
circuit terminal 8. Verify the scan tool park lamp switch parameter is active.
If not the specified value, test the park lamp switch signal circuit for an open/high
resistance. If the circuit tests normal, replace the BCM.
4. If all circuits test normal, test or replace the headlamp switch.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Headlamp Switch Replacement (without RPO SLT) or Headlamp Switch
Replacement (with RPO SLT)
Control Module References for BCM replacement, setup, and programming
DTC B2580
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 B2580 00
Headlamp High Beam Control Circuit
Diagnostic Fault Information
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
Headlamp High Beam Relay
Control Circuit
2
1
B2580 00
-
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Circuit/System Description
Voltage is applied at all times to the high beam headlamp relay from battery voltage. When the
multifunction switch is placed in either the FTP or HIGH position, ground is applied to the body
control module (BCM). The BCM then applies a ground to the headlamp high beam relay control
circuit. This engages the relay and applies voltage through the HI HEADLAMP fuses to both left
and right high beam headlamps.
Conditions for Running the DTC
The headlamps are commanded ON.
Headlamp dimmer switch must be in the high beam position.
Conditions for Setting the DTC
The BCM detects a short to voltage on the headlamp high beam relay control circuit.
Action Taken When the DTC Sets
The high beam headlamps are inoperative.
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
1. Headlamps Inoperative - High Beams
2. Headlamps Always On - High Beams
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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 High Beam output control on the scan tool. The High Beam Relay
Command parameter in the data list should display On and the high beam headlamps should
illuminate.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector X4 at the BCM.
2. Low beam headlamps ON, verify the high beam headlamps are not on.
If the high beam headlamps are on, test the high beam relay control circuit for a short
to ground. If the circuit tests normal replace the underhood fuse block.
3. Install a 10A fused jumper wire between the relay control circuit terminal 16 and ground.
Verify the high beam headlamps are on.
If the high beam headlamps are not on, test the high beam relay control circuit for a
short to voltage or an open/high resistance. If the circuit tests normal replace the
underhood fuse block.
4. If all circuits test normal, replace the BCM.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Underhood Electrical Center or Junction Block Replacement
Control Module References for BCM replacement, setup, and programming
DTC B2585
Diagnostic Instructions
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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