Chevrolet Silverado / GMC Sierra. Service manual — part 2484

each rear doors one at a time. The reading should change between Door Open and Door
Closed

If the Ctsy. Lamp Actv. Reason parameter does not change between Door Open and
Door Closed, refer to Door Open Switch Test-Rear below.

5. Ignition ON and all doors closed, observe the scan tool BCM Ctsy. Lamp Actv. Reason

parameter while turning the dome lamp switch ON and OFF. The reading should change
between Off and Manual.

If the Ctsy. Lamp Actv. Reason parameter does not change between Off and Manual,
refer to Dome/Interior Lamp Switch Test below.

6. Ignition ON and all doors closed, observe the scan tool BCM Ctsy. Lamp Actv. Reason

parameter while turning the interior lamp defeat switch ON and OFF. The reading should
change between Off and Manual Defeat.

If the Ctsy. Lamp Actv. Reason parameter does not change between Off and Manual,
refer to Dome/Interior Lamp Switch Test below.

Circuit/System Testing

Courtesy Lamp Control Circuit Test

1. Ignition OFF, disconnect the harness connector at an affected lamp bulb.

2. Test for less than 1 ohm of resistance between the ground circuit terminal and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal and the ground circuit terminal.

4. Ignition ON, command the Courtesy Lamps output control on and off with the scan tool.

The test lamp should turn on and off.

If the test lamp is always ON, test the control circuit for a short to voltage. If the
circuit tests normal, replace the BCM.

If the test lamp is always OFF, test the control circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the bulb.

Door Open Switch Test-Front

1. Ignition OFF, disconnect the harness connector at the affected door latch.

2. Test for less than 1 ohm of resistance between the listed ground circuit terminal and ground.

Driver terminal 8

Passenger terminal 3

2008 Chevrolet Silverado 1500

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

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool door open switch parameter is inactive.

If not the specified value, test the listed signal circuit terminal for a short to ground. If
the circuit tests normal, replace the affected door switch.

Driver terminal 7

Passenger terminal 2

4. Install a 3A fused jumper wire between the listed signal circuit terminal and low reference

circuit terminal. Verify the scan tool door open switch parameter is active.

Driver terminal 7 to terminal 8

Passenger terminal 2 to terminal 3

If not the specified value, test the signal circuit for a short to voltage or an open/high
resistance. If the circuit tests normal, replace the affected door switch.

5. If all circuits test normal, test or replace the affected door latch.

Door Open Switch Test-Rear

1. Ignition OFF, disconnect the harness connector at the affected door latch.

2. Test for less than 1 ohm of resistance between the listed ground circuit terminal and ground.

Left terminal 6

Right terminal 3

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool passenger door open switch parameter is Closed.

If not the specified value, test the listed signal circuit terminal for a short to ground. If
the circuit tests normal, replace the BCM.

Left terminal 5

Right terminal 2

4. Install a 3A fused jumper wire between the listed signal circuit terminal and low reference

circuit terminal. Verify the scan tool passenger door open switch parameter is Open.

Left terminal 5 to terminal 6

Right terminal 2 to terminal 3

If not the specified value, 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 affected door latch.

Dome/Interior Lamp Switch Test

2008 Chevrolet Silverado 1500

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

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

2. Test for less than 1 ohm of resistance between the ground circuit terminal 8 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Ctsy. Lamp Actv. Reason parameter is Off.

If not the parameter is Manual or Manual Defeat, test the affected signal circuit
terminal for a short to ground. If the circuit tests normal, replace the BCM.

Manual terminal 12

Manual Defeat terminal 9

4. Install a 3A fused jumper wire between the signal circuit terminal 12 and the ground circuit

terminal 8. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Manual.

If not the specified value, test the signal circuit for a short to voltage 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 9 and the ground circuit

terminal 8. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Manual Defeat.

If not the specified value, test the signal circuit for a short to voltage 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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Dome Lamp Replacement

Front Side Door Lock Replacement

Rear Door Lock Replacement (Extended Cab Upper) or Rear Door Lock
Replacement (Crew Cab) or Rear Door Lock Replacement (Extended Cab Lower)

Headlamp Switch Replacement (without RPO SLT) or Headlamp Switch
Replacement (with RPO SLT)

Control Module References for BCM, driver door switch, or passenger door switch
replacement, programming, and setup.

COURTESY LAMPS MALFUNCTION (W/O AN3)

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.

2008 Chevrolet Silverado 1500

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

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Description

Voltage for the courtesy lamps is supplied from body control module (BCM). When a door is
opened, a signal is applied to the BCM. The BCM then applies voltage to the courtesy lamps
voltage supply circuit and the components on that circuit.

Reference Information

Schematic Reference

Interior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Dome Lamp Switch Signal

1

3

-

-

Interior Lamp Defeat Switch
Signal

2

4

-

-

Door Open Switch Signal

1

-

-

Courtesy Lamp Control

B2615

2

1

-

1. Courtesy lamps always on
2. Courtesy lamps inoperative
3. Courtesy lamps inoperative from dome lamp switch
4. Manual defeat switch inoperative
3. Courtesy lamps not on with door open

2008 Chevrolet Silverado 1500

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