Chevrolet Silverado / GMC Sierra. Manual — part 2472

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, cover the ambient light sensor. Vary the interior lamp dimming switch from dim to
full bright. The I/P lamps should dim and then become full bright.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the headlamp switch.

2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and

B+.

If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Dimming Control Signal parameter is less than 0.1 volts.

If greater than the specified range, test the signal circuit terminal 13 for a short to
voltage. If the circuit tests normal, replace the BCM.

4. Ignition ON, test for 12 volts between the I/P dimming voltage reference circuit terminal 15

and ground.

If less than the specified value, test the voltage reference circuit for a short to ground
or an open/high resistance. If the circuit tests normal, replace the BCM.

5. Install a 3A fused jumper wire between the signal circuit terminal 13 and the voltage

reference circuit terminal 15. Verify the scan tool BCM Dimming Control Signal parameter
is greater than 2.6 volts.

If less than the specified range, test the signal circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the BCM.

6. If all circuits test normal, test or replace the headlamp switch.

Repair Procedures

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

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 B2530

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 B2530 00

Front Fog Lamp Control Circuit

Diagnostic Fault Information

Circuit/System Description

Voltage is applied at all times to the fog lamp relay. When the fog lamp switch is placed in the
ON position, a ground signal is applied to the body control module (BCM) through the fog lamp
switch signal circuit. The BCM then applies a ground to the front fog lamp control circuit. This
engages the fog lamp relay and applies voltage through the FOG LAMP fuse to the front fog
lamps.

Conditions for Running the DTC

The ignition is ON.

Park lamps must be ON and the fog lamps must be commanded ON.

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Front Fog Lamp Relay
Control Circuit

1

2

B2530 00

-

1. Fog Lamps Always On

2. Fog Lamps Inoperative

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Conditions for Setting the DTC

The BCM detects a short to voltage on the front fog lamp control circuit.

Action Taken When the DTC Sets

The front fog lamps do not illuminate.

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

Fog 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 Fog Lamps output control on the scan tool. The Front Fog Lamp Relay
Command parameter in the data list should display On and the front fog lamps should illuminate.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Circuit/System Testing

1. Ignition OFF, remove the fog lamp relay in the underhood fuse block.

2. Ignition ON, test for voltage at the relay control circuit terminal 86 of the underhood fuse

block.

If voltage is present, test the control circuit for a short to voltage. If all
circuits/connections test normal, replace the fog lamp relay.

If voltage is not present, replace the BCM.

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 B2545

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 B2545 00

Backup Lamps Circuit

Diagnostic Fault Information

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Backup Lamps Voltage
Supply

B2545 00

1

2

-

1. Backup Lamps Inoperative

2. Backup Lamps Always On

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado