Chevrolet Silverado / GMC Sierra. Service 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