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Contents Wiring diagrams Section: Exterior Lights All sections

Lighting Systems Chevrolet Cab & Chassis Silverado 3500 HD

Exterior Lights 53 illustrations ~25823 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Center High-Mounted Stop Cargo Lamp Mounting Screws2.5 N.m22 lb in
Headlamp Ballast Screws2 N.m18 lb in
Headlamp Mounting Screws6 N.m53 lb in
License Plate Lamp Screws2 N.m18 lb in
Power Vacuum Brake Booster Pushrod Retaining Bolt10 N.m89 lb in
Rear Tail/Turn Signal Lamp Assembly Screws2 N.m18 lb in
Rear Side Marker Lamp Screws2.5 N.m22 lb in
Roof Marker Lamp Screws - Center2 N.m18 lb in
Roof Marker Lamp Screws - Outer2 N.m18 lb in
Tail Lamp Screws2 N.m18 lb in

Scheme 1

Scheme 1: Headlights/Daytime Running Lights (DRL) Schematics
Scheme 1: Headlights/Daytime Running Lights (DRL) Schematics

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

Scheme 4

Scheme 4: Fog Lights Schematics
Scheme 4: Fog Lights Schematics

Scheme 5

Scheme 5: Exterior Lights Schematics
Scheme 5: Exterior Lights Schematics

Scheme 6

Scheme 6
Scheme 6

Scheme 7

Scheme 7
Scheme 7

Scheme 8

Scheme 8
Scheme 8

Scheme 9

Scheme 9
Scheme 9

Scheme 10

Scheme 10
Scheme 10

Scheme 11

Scheme 11
Scheme 11

Scheme 12

Scheme 12
Scheme 12

Scheme 13

Scheme 13: Interior Lights Schematics
Scheme 13: Interior Lights Schematics

Scheme 14

Scheme 14
Scheme 14

Scheme 15

Scheme 15
Scheme 15

Scheme 16

Scheme 16
Scheme 16

Scheme 17

Scheme 17: Interior Lights Dimming Schematics
Scheme 17: Interior Lights Dimming Schematics

Scheme 18

Scheme 18
Scheme 18

Scheme 19

Scheme 19
Scheme 19

Scheme 20

Scheme 20
Scheme 20

Scheme 21

Scheme 21
Scheme 21

DIAGNOSTIC CODE INDEX

DTCDescription
DTC B1395B1395 03: Voltage Below Threshold B1395 07: Voltage Above Threshold
DTC B2530B2530 00: Front Fog Lamp Control Circuit
DTC B2545B2545 00: Backup Lamps Circuit
DTC B25752575 00: Headlamp Low Beam Control Circuit
DTC B257AB257A 00: Headlamp Switch Input Signal Mismatch
DTC B2580B2580 00: Headlamp High Beam Control Circuit
DTC B2585B2585 00: Park Lamp Control Circuit
DTC B2600B2600 00: Daytime Running Lamp Control Circuit
DTC B2610B2610 00: Passenger Compartment Dimming 1 Circuit B2610 01: Passenger Compartment Dimming 1 Circuit Short to Battery B2610 02: Passenger Compartment Dimming 1 Circuit Short to Ground B2610 04: Passenger Compartment Dimming 1 Circuit Open
DTC B2615B2615 00: Passenger Compartment Dimming 2 Circuit B2615 01: Passenger Compartment Dimming 2 Circuit Short to Battery B2615 02: Passenger Compartment Dimming 2 Circuit Short to Ground B2615 04: Passenger Compartment Dimming 2 Circuit Open
DTC B2625B2625 00: Display Dimming Pulse Width Modulation (PWM) Output Circuit
DTC B2645B2645 03: Ambient Light Sensor Circuit Voltage Below Threshold B2645 07: Ambient Light Sensor Circuit Voltage Above Threshold
DTC B2652B2652 00: Passenger Compartment Dimming 3
DTC B3445B3445 00: Stop Lamp Circuit
DTC B3600B3600 03: Voltage Below Threshold B3600 07: Voltage Above Threshold
DTC B3884B3884 00: Center High Mounted Stop Lamp (CHMSL) Circuit
DTC C0277, C0297, or C0890C0277 00: Brake Pedal Position Sensor Calibration Not Learned C0297 00: Brake Applied Output Circuit C0890 00: Device Voltage Reference Output 3 Circuit Voltage Out of Range

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Lighting

Begin the system diagnosis with the Diagnostic System Check - Vehicle . The Diagnostic System Check - Vehicle will provide the following information

  1. The identification of the control modules which command the system
  2. The ability of the control modules to communicate through the serial data circuit
  3. The identification of any stored diagnostic trouble codes (DTCs) and their status

The Use of the Diagnostic System Check - Vehicle will identify the correct procedure for diagnosing the system and where the procedure is located.

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
I/P Dimming Voltage ReferenceB1395 03 and B3600 03B1395 03, B2652 00, and B3600 03B1395 07B1395 03, B1395 07
Stop Lamp SignalB1395 03 and B3600 03

Circuit/System Description

Voltage for the interior backlighting components and stop lamp switch activation signal is supplied from the body control module (BCM). The BCM applies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimming switch, which is part of the headlamp switch. When the dimming switch is placed in the desired position, the dimmed voltage setting is applied from the interior lamp dimming switch through the I/P dimming control circuit to the BCM. The BCM then applies the dimmed voltage to the I/P lamps supply voltage circuit and they dim to the correct level.

The stop lamp switch is also supplied voltage on the same circuit for a stop lamp OFF signal to the BCM. When the stop lamp switch is activated the voltage signal circuit to the BCM is opened prompting the BCM to illuminate the stop lamps.

Conditions for Running the DTC

Battery Voltage must be between 9-16 volts.

B1395 03

The BCM detects a voltage that is lower than 0.33 volt on the I/P dimming voltage reference circuit.

B1395 07

The BCM detects a voltage that is greater than 4.97 volts on I/P dimming voltage reference circuit.

Action Taken When the DTC Sets

  1. The I/P dimmer switch will not operate.
  2. The I/P dimming lamps will not illuminate.

Conditions for Clearing the DTC

  1. The condition responsible for setting the DTC no longer exists.
  2. history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

  1. «Interior Lights Dimming Schematics»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Exterior Lights Schematics»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__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. Verify that a test lamp illuminates between B+ and the ground circuit terminal 8. 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 B+ 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 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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Fog Lamp Relay B+11
Fog Lamp Switch Signal222
Fog Lamp Relay Control11B2530 00
Fog Lamp Control111
Fog Lamp - LF Ground1
Fog Lamp - RF Ground1
Fog Lamp Switch Ground2
1. Fog Lamps Malfunction 2. Fog Lamp Switch Malfunction

The fog lamp relay is supplied with battery voltage at all times. The fog lamp switch signal circuit is grounded momentarily by pressing the fog lamp switch. The body control module (BCM) energizes the fog lamp relay by applying ground to the fog lamp relay control circuit. When the fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the FOG LAMP fuse to the fog lamp supply voltage circuit which illuminates the fog lamps.

  1. Battery voltage must be between 9-16 volts.
  2. Fog lamps ON.

Conditions for Setting the DTC

DTC B2530 00 will set when the BCM detects a short to voltage in the fog lamp relay control circuit for 5 seconds or greater.

Actions Taken When the DTC Sets

When DTC B2530 00 is present, the fog lamps will not operate when the park lamps are ON and the fog lamp switch is active.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the fog lamp relay.
  2. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  3. Command the Fog Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the 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 fog lamp relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Relay Replacement (Attached to Wire Harness)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Backup Lamp Relay B+11
Backup Lamp Switch Signal111
Backup Lamp Relay ControlB2545 0011
Backup Lamps Control111
Backup Lamp - Left Ground1
Backup Lamp - Right Ground1
Backup Lamp Switch Ground1
1. Backup Lamps Malfunction

Automatic Transmission

When the transmission is placed in the REVERSE position, the transmission control module (TCM) sends a serial data message to the body control module (BCM). The message indicates that the gear selector is in the REVERSE position. The BCM applies voltage to the backup lamp relay control circuit energizing the backup lamp relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow through the VEH BCK/UP fuse to the left and right backup lamps. The BCM also supplies voltage the to inside rearview mirror via the backup lamp relay control circuit for automatic day/night operation. Once the driver moves the gear selector out of the REVERSE position, a serial data message is sent by the TCM requesting the BCM to remove voltage from the backup lamp control circuit.

Manual Transmission

When the transmission is placed in the REVERSE position, the backup lamp switch contacts close supplying ground to the engine control module (ECM) via the backup lamp switch signal circuit. The ECM responds by sending a serial data message to the body control module (BCM) indicating the gear selector is in the REVERSE position. The BCM applies voltage to the backup lamp relay control circuit energizing the backup lamp relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow through the VEH BCK/UP fuse to the left and right backup lamps. The BCM also supplies voltage the to inside rearview mirror via the backup lamp relay control circuit for automatic day/night operation. Once the driver moves the gear selector out of the REVERSE position, the backup lamp switch contacts open and a serial data message is sent by the ECM requesting the BCM to remove voltage from the backup lamp relay control circuit.

Battery voltage must be between 9-16 volts.

DTC B2545 00 will set when the BCM detects a short to ground in the backup lamp relay control circuit.

When DTC B2545 00 is present, the backup lamps will not operate.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
  2. Connect a test lamp between the control circuit terminal 9 and ground.
  3. Command the backup lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. 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.
  4. Ignition OFF, connect the harness connector at the inside rearview mirror. Disconnect the X5 harness connector at the underhood fuse block.
  5. Connect a test lamp between the control circuit terminal H8 and ground.
  6. Command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. 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.
  7. If all circuits test normal, replace the underhood fuse block.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
HDLP LO/HID Relay B+111
HI Beam Relay B+111
Flash to Pass Switch Signal111
Headlamp Switch Headlamps ON SignalB257A 0011
Headlamp Switch Headlamps OFF SignalB257A 0011
Headlamp Switch High Beam Signal111
Headlamp High Beam Relay Control11B2580 00
Headlamp Low Beam Relay Control11B2575 00
Headlamp and Panel Dimmer Switch Ground1
LF Headlamp Ground1
RF Headlamp Ground1
Turn Signal/Multifunction Switch Ground1
1. Headlamps Malfunction

When the headlamp switch is placed in the headlamp ON position, ground is applied to the body control module (BCM) through the headlamp low beam signal circuit. The BCM then applies ground to the headlamp low beam relay control circuit which energizes the low beam relay. With the low beam relay energized, the switch contacts close allowing battery voltage to flow through the LO HDLP fuses to the low beam headlamps. Ground for the left headlamp is supplied at G100 and the right headlamp receives ground at G101.

  1. Battery voltage must be between 9-16 volts.
  2. Headlamps ON.

DTC B2575 00 will set when the BCM detects a short to voltage in the headlamp low beam relay control circuit.

When DTC B2575 00 is present, the low beam headlamps will not operate.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the low beam relay.
  2. Connect a test lamp between the control circuit terminal 85 and the B+ circuit terminal 86.
  3. Command the Low Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the low beam relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Relay Replacement (Attached to Wire Harness)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
HDLP LO/HID Relay B+111
HI Beam Relay B+111
Flash to Pass Switch Signal111
Headlamp Switch Headlamps ON SignalB257A 0011
Headlamp Switch Headlamps OFF SignalB257A 0011
Headlamp Switch High Beam Signal111
Headlamp High Beam Relay Control11B2580 00
Headlamp Low Beam Relay Control11B2575 00
Headlamp and Panel Dimmer Switch Ground1
LF Headlamp Ground1
RF Headlamp Ground1
Turn Signal/Multifunction Switch Ground1
1. Headlamps Malfunction

When the headlamp switch is placed in the AUTO position, the body control module (BCM) receives a ground signal through the headlamp switch headlamps OFF signal circuit. The headlamp switch headlamps ON signal circuit and the park lamp switch signal circuit are both open and have no ground signal. When the headlamp switch is placed in the PARK or HEAD position, the BCM will receive a ground signal through the headlamp switch headlamps ON signal circuit and the park lamp switch signal circuit. The headlamp switch headlamps OFF signal circuit will be open and have no ground signal.

Battery voltage must be between 9-16 volts.

DTC B257A 00 will set when the BCM detects a short to ground on the headlamp switch headlamps OFF signal circuit or the headlamp switch headlamps ON signal circuit.

  1. When DTC B257A 00 is present on the headlamp switch headlamps OFF signal circuit, the low beam headlamps are always ON in the AUTO position. The headlamp switch operates in all positions other than AUTO. The AUTO headlamp defeat is inoperative.
  2. When DTC B257A 00 is present on the headlamp switch headlamps ON signal circuit, the low beam headlamps are always ON. The BCM disregards all headlamp switch inputs.
  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the X2 harness connector at the BCM.
  2. Connect a test lamp between B+ and the signal circuit terminal 17.
  3. Turn the headlamp switch between the headlamp AUTO and headlamp OFF positions. The test lamp should turn ON and OFF as the switch is cycled. If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp switch. If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit tests normal, replace the headlamp switch.
  4. Connect a test lamp between B+ and the signal circuit terminal 12.
  5. Turn the headlamp switch to the ON and OFF positions. The test lamp should turn ON and OFF as the switch is cycled. If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp switch. If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit tests normal, replace the headlamp switch.
  6. If all circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
HDLP LO/HID Relay B+111
HI Beam Relay B+111
Flash to Pass Switch Signal111
Headlamp Switch Headlamps ON SignalB257A 0011
Headlamp Switch Headlamps OFF SignalB257A 0011
Headlamp Switch High Beam Signal111
Headlamp High Beam Relay Control11B2580 00
Headlamp Low Beam Relay Control11B2575 00
Headlamp and Panel Dimmer Switch Ground1
LF Headlamp Ground1
RF Headlamp Ground1
Turn Signal/Multifunction Switch Ground1
1. Headlamps Malfunction

When the turn signal/multifunction switch is placed in the headlamps high or flash to pass (FTP) position, ground is applied to the body control module (BCM) through the headlamp high beam signal circuit or the flash to pass signal circuit. The BCM applies ground to the headlamp high beam relay control circuit which energizes the high beam relay. With the high beam relay energized, the switch contacts close allowing battery voltage to flow through the HI HEADLAMP fuses to the high beam headlamps. Ground for the left headlamp is supplied at G100 and the right headlamp receives ground at G101.

  1. Battery voltage must be between 9-16 volts.
  2. Headlamps ON.

DTC B2580 00 will set when the BCM detects a short to voltage in the headlamp high beam relay control circuit.

When DTC B2580 00 is present, the high beam headlamps and flash to pass (FTP) will not operate.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
  2. Connect a test lamp between the control circuit terminal C3 and B+.
  3. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, replace the underhood fuse block.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Park Lamp Relay B+11
Park Lamp Switch ON Signal111
Park Lamp Relay Control11B2585 00
Park Lamp Control111
License Lamp Ground1
Headlamp and Panel Dimmer Switch Ground22
Park Lamps - LF Ground1
Park Lamps - RF Ground1
Tail/Stop and Turn Signal Lamps - LR Ground1
Tail/Stop and Turn Signal Lamps - RR Ground1
Turn Signal/Multifunction Switch Ground1
1. Park, License, and/or Tail Lamps Malfunction 2. Headlamp Switch Malfunction

Battery positive voltage is applied at all times to both the coil and switch sides of the PARK LAMP Relay located in the underhood fuse block. When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the park lamp signal circuit to the body control module (BCM). The BCM responds by applying ground to the PARK LAMP Relay control circuit. This energizes the PARK LAMP Relay coil causing the relay switch contacts to close allowing B+ to flow through the LT PRK fuse, RT PRK fuse, and the TRLR PRK fuse, to all of the park, tail, license, and marker lamps.

  1. Battery voltage must be between 9-16 volts.
  2. Park lamps ON.

DTC B2585 00 will set when the BCM detects a short to voltage in the PARK LAMP Relay control circuit.

When DTC B2585 00 is present, the park lamps will not operate.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the PARK LAMP Relay.
  2. Connect a test lamp between the relay control circuit terminal 86 and the B+ circuit terminal 85.
  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. 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Relay Replacement (Attached to Wire Harness)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
DRL Relay B+22
Ambient Light Sensor SignalB2645 03B2645 07B2645 07
Daytime Running Lamps Control22B2600 00
Headlamp - Left Front Low Beam Control111
Headlamp - Right Front Low Beam Control111
Ambient Light Sensor GroundB2645 07
Headlamp - Left Front Ground1
Headlamp - Right Front Ground1
1. Headlamps Malfunction 2. Daytime Running Lamps Malfunction

The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The body control module (BCM) monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the DRLs ON by applying ground to the DRL relay via the DRL relay control circuit. When the BCM applies ground to the DRL relay control circuit, the DRL relay coil energizes causing the relay switch contacts to close. With the DRL relay switch contacts closed, battery voltage flows through the DRL 1 and DRL 2 fuses to the left and right LO HDLP fuses to the low beam headlamps. The DRL control circuit that supplies the low beam headlamp fuses with voltage contains a loop of wire that acts as resistance. This resistance is responsible for the low beam headlamps illuminating at a reduced intensity. Any function or condition that turns on the headlamps will cancel DRL operation.

  1. Battery voltage must be between 9-16 volts.
  2. Headlamp switch in AUTO position.

DTC B2600 00 will set when the BCM detects a short to voltage in the DRL relay control circuit.

The BCM will disable the DRL relay control circuit.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, verify with a scan tool the Park Brake Switch parameter displays Released.

  1. If not the specified value, refer to «Brake Warning Indicator Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/mechanical-hydraulic/#hydraulic-brake-system) .
  1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
  2. Connect a test lamp between the control circuit terminal H4 and B+.
  3. Command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the 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, replace the underhood fuse block.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
IS LPS Fuse B+B1395 03B1395 03
Headlamp and Panel Dimmer Switch SignalB1395 0311
I/P Lamps Dimmer Switch SignalB2652 0011
I/P Dimming Voltage ReferenceB1395 0311
Indicator Dimming ControlB2625 0011
LED Backlight Dimming ControlB2610 0011
Headlamp and Panel Dimmer Switch Ground1
1. Interior Backlighting Malfunction

The instrument panel (I/P) lamp dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit and the interior backlighting components dim to the requested level. Ground for the I/P dimmer switch is provided at G201.

  1. Battery voltage must be between 9-16 volts.
  2. Park lamps ON.

DTC B2610 00 will set when the BCM detects a short to ground in the LED backlight dimming control circuit.

The BCM will not dim or illuminate any indicators supplied by the LED backlight dimming control circuit.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the appropriate component.
  2. Verify that a test lamp illuminates between the listed ground circuit terminal and B+. Left steering wheel switch terminal 8 Right steering wheel switch terminal 1 PTO switch terminal 5 Trailer brake controller switch terminal 8 DIC switch terminal 5 HVAC control module terminal 10 X2 I/P multifunction switch terminal 3 If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the listed LED dimming control circuit terminal and ground. Left steering wheel switch terminal 6 Right steering wheel switch terminal 2 PTO switch terminal 6 Trailer brake controller switch terminal 7 DIC switch terminal 4 HVAC control module terminal 1 X2 I/P multifunction switch terminal 4
  4. Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states. If the test lamp is always off, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the appropriate component.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. Refer to the appropriate replacement procedure for the component causing the condition.
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM, driver door lock and side window switch, or passenger door lock and side window switch replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Courtesy Lamps Voltage SupplyB2615 00 or B2615 02B2615 00 or B2615 04B2615 00 or B2615 01
Courtesy Lamp Ground1
1. Courtesy Lamps Malfunction

Voltage for the courtesy lamps is supplied from body control module (BCM), driver door switch, and passenger door switch. When a door is opened, a signal is applied to the door module. The door module then applies a message on the low speed GMLAN serial data communication circuit to the BCM to activate the courtesy lamps. The BCM then applies voltage to the courtesy lamps voltage supply circuit and the components on that circuit.

The ignition is ON, the BCM, driver door switch, and passenger door switch attempt to illuminate the courtesy lamps.

The BCM, driver door lock and side window switch, or passenger door lock and side window switch detects a short to ground, short to voltage, or open on the courtesy lamp voltage supply circuit.

The BCM, driver door lock and side window switch, and passenger door lock and side window switch cease attempts to illuminate the courtesy lamps.

  1. The conditions for setting the DTC are no longer present.
  2. A history DTC clears after 100 malfunction-free ignition cycles.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, activate the Courtesy Lamps output control with the scan tool. The interior courtesy lamps should illuminate.

  1. Ignition OFF, disconnect the harness connector at the inoperative lamp.
  2. Test for less than 5.0 ohms 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 inoperative lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. Refer to the appropriate replacement procedure for the component causing the condition.
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM, driver door lock and side window switch, or passenger door lock and side window switch replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
IS LPS Fuse B+B1395 03B1395 03
Headlamp and Panel Dimmer Switch SignalB1395 0311
I/P Lamps Dimmer Switch SignalB2652 0011
I/P Dimming Voltage ReferenceB1395 0311
Indicator Dimming ControlB2625 0011
LED Backlight Dimming ControlB2610 0011
Headlamp and Panel Dimmer Switch Ground1
1. Interior Backlighting Malfunction

The instrument panel (I/P) dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit and the interior backlighting components dim to the requested level.

  1. Battery voltage must be between 9-16 volts.
  2. Park lamps ON.

DTC B2625 00 will set when the BCM detects a short to ground in the LED indicator dimming control circuit.

When DTC B2625 00 is present, the BCM will not illuminate the LEDs supplied by the LED indicator dimming control circuit.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, headlamp switch to PARK, vary the interior lamp dimming switch from dim to full bright. The LED lamps should dim and then become full bright.

  1. Ignition OFF, disconnect the harness connector at the appropriate component.
  2. Connect a test lamp between the listed LED dimming control circuit terminal and ground. IP multifunction switch terminal 6 4wd mode switch terminal 4 PTO switch terminal 7
  3. Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states. If the test lamp is always OFF, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the appropriate component.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. Refer to the appropriate replacement procedure for the component causing the condition.
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
DRL Relay B+22
Ambient Light Sensor SignalB2645 03B2645 07B2645 07
Daytime Running Lamps Control22B2600 00
Headlamp - Left Front Low Beam Control111
Headlamp - Right Front Low Beam Control111
Ambient Light Sensor GroundB2645 07
Headlamp - Left Front Ground1
Headlamp - Right Front Ground1
1. Headlamps Malfunction 2. Daytime Running Lamps Malfunction

The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The body control module (BCM) monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the DRLs ON by applying ground to the DRL relay via the DRL relay control circuit. When the BCM applies ground to the DRL relay control circuit, the DRL relay coil energizes causing the relay switch contacts to close. With the DRL relay switch contacts closed, battery voltage flows through the DRL 1 and DRL 2 fuses to the left and right LO HDLP fuses to the low beam headlamps. The DRL control circuit that supplies the low beam headlamp fuses with voltage contains a loop of wire that acts as resistance. This resistance is responsible for the low beam headlamps illuminating at a reduced intensity. Any function or condition that turns on the headlamps will cancel DRL operation.

Battery voltage must be between 9-16 volts.

B2645 03

The DTC will set when the BCM detects a short to ground in the ambient light sensor signal circuit.

B2645 07

The DTC will set when the BCM detects a short to voltage or an open/high resistance in the ambient light sensor signal circuit.

  1. Automatic lamp control (ALC) is inoperative.
  2. The BCM defaults to low light status and commands the low beam headlamps ON.
  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
  2. Ignition OFF, scan tool OFF, doors CLOSED, test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground. Terminal B - with C67/C42 Terminal C - with CJ2 If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.5 volts. If less than the specified range, test the appropriate signal circuit terminal listed below for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. Terminal A - with C67/C42 Terminal D - with CJ2
  4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 volts. Terminal A - with C67/C42 Terminal D - with CJ2 If greater than the specified range, 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, replace the ambient light sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Ambient Light Sensor Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
IS LPS Fuse B+B1395 03B1395 03
Headlamp and Panel Dimmer Switch SignalB1395 0311
I/P Lamps Dimmer Switch SignalB2652 0011
I/P Dimming Voltage ReferenceB1395 0311
Indicator Dimming ControlB2625 0011
LED Backlight Dimming ControlB2610 0011
Headlamp and Panel Dimmer Switch Ground1
1. Interior Backlighting Malfunction

The instrument panel (I/P) lamp dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit and the interior backlighting components dim to the requested level. Ground for the I/P dimmer switch is provided at G201.

  1. Battery voltage must be between 9-16 volts.
  2. Park lamps ON.

The BCM detects a short to ground in the I/P lamps dimmer switch signal circuit.

The BCM will not DIM or illuminate any I/P lamps supplied by the I/P lamps dimmer switch signal circuit.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the appropriate component.
  2. Ignition OFF, verify that a test lamp illuminates between the listed ground circuit terminal and B+. Headlamp Switch terminal 8 Sunroof switch terminal 5 Front door lock switch terminal B - w/o AN3 Driver window switch terminal A X2 - w/o AN3 Front passenger window switch terminal F - w/o AN3 OSRVM switch terminal G - w/o AN3 Transfer case shift control switch terminal 6 Roof beacon switch terminal 1 Sliding rear window switch terminal D Rear window switch terminal F If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the listed backlighting control circuit terminal and ground. Headlamp Switch terminal 7 Sunroof switch terminal 3 Front door lock switch terminal A - w/o AN3 Driver window switch terminal 1 X1 - w/o AN3 Front passenger window switch terminal B - w/o AN3 OSRVM switch terminal E - w/o AN3 Transfer case shift control switch terminal 5 Roof beacon switch terminal 2 Sliding rear window switch terminal E Rear window switch terminal B
  4. Command the Dimming Test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states. If the test lamp is always OFF, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the appropriate component.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. Refer to the appropriate replacement procedure for the component causing the condition.
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Stop Lamp Relay ControlB3445 0011
Tail/Stop Lamp Control - Left111
Tail/Stop Lamp Control - Right111
Stop Lamp Switch Signal111
Stop Lamp Switch B+ Voltage ReferenceB1395 03, B3600 0311
Stop Lamp Relay Switch B+11
Center High Mounted Stop Lamp (CHMSL) Ground2
Tail/Stop Lamp Ground - Left1
Tail/Stop Lamp Ground - Right1
Stop Lamp Relay Ground1
1. Stop Lamps Malfunction 2. Center High Mounted Stop Lamp (CHMSL) Malfunction

The stop lamp switch is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a low reference signal and a B+ reference voltage to the stop lamp switch. When the stop lamp switch contacts close indicating the brakes have been applied, the BCM will apply battery voltage to stop lamp relay control circuit and the center high mounted stop lamp (CHMSL). When the stop lamp relay receives battery voltage from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage to the STOP LP fuse to illuminate the left and right stop lamps.

  1. Battery voltage must be between 9-16 volts.
  2. Brakes APPLIED.

The DTC will set when the BCM detects a short to ground in the CHMSL control circuit when the stop lamps are being commanded ON.

The BCM will not illuminate the CHMSL.

  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Diagnostic Aids

IMPORTANTThe stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation .

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the CHMSL.
  2. Test for less than 5.0 ohms between the ground circuit terminal B 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 A and the ground circuit terminal B.
  4. Ignition ON, command the stop lamps ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states. 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, replace the CHMSL.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Tail Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Tail Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
IS LPS Fuse B+B1395 03B1395 03
Headlamp and Panel Dimmer Switch SignalB1395 0311
I/P Lamps Dimmer Switch SignalB2652 0011
I/P Dimming Voltage ReferenceB1395 0311
Indicator Dimming ControlB2625 0011
LED Backlight Dimming ControlB2610 0011
Headlamp and Panel Dimmer Switch Ground1
1. Interior Backlighting Malfunction

The instrument panel (I/P) lamp dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit and the interior backlighting components dim to the requested level. Ground for the I/P dimmer switch is provided at G201.

Battery voltage must be between 9-16 volts.

DTC B3600 03 will set when the BCM detects a short to ground or an open/high resistance in the I/P dimmer switch signal circuit.

  1. The I/P dimmer switch will not operate.
  2. The I/P dimming lamps will not illuminate.
  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, headlamp switch to HEAD, vary the interior lamp dimming switch from dim to full bright. The I/P lamps should dim and then become full bright.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
CHMSL Relay ControlB3884 0012
CHMSL Control112
CHMSL Relay Control1
CHMSL Ground1
Stop Lamp Switch Malfunction Stop Lamp Malfunction

When the brake pedal is applied, the brake pedal switch normally closed contact signal circuit voltage is interrupted to the body control module (BCM). Upon brake activation, the body control module (BCM) applies voltage through the CHMSL relay control circuit to the coil side of the relay. Ground is applied at all times to the other side of the CHMSL relay coil therefore the relay is now energized. Battery voltage is then applied through the switch side of the relay, the CHMSL fuse, and the CHMSL control circuit to the center high mounted stop lamp (CHMSL). The CHMSL is grounded at G 200.

  1. The ignition is ON.
  2. The stop lamps must be commanded ON.

The BCM detects a short to ground in the CHMSL relay control circuit when the stop lamps are commanded ON.

The CHMSL does not illuminate.

  1. The conditions for setting the DTC are no longer present.
  2. A history DTC clears after 100 malfunction-free ignition cycles.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connectors at the center high mounted stop lamp.
  2. Test for less than 5.0 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the stop lamp control circuit terminal A and ground circuit terminal B.
  4. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.
  5. If all circuits test normal, test or replace the center high mounted stop lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Battery voltage must be between 9-16 volts.

In the event that DTC C0277, C0297, or C0890 sets as current in the body control module (BCM) is an indication of a possible internal BCM malfunction or programming error. There are no external circuits available to diagnose on this vehicle with respect to these DTCs.

When DTC C0277 is set as current, the vehicle may not start.

  1. For DTC C0277 the ignition must be cycled before the code can be cleared.
  2. A history DTC will clear once 50 malfunction-free ignition cycles have occurred.
  3. A DTC will not clear the current status until the next ignition cycle.

These DTCs may set as current after the replacement of an electronic brake control module (EBCM) or engine control module (ECM). If a control module has been replaced, ensure that the programming procedure and all recalibration procedures have been completed successfully before addressing these DTCs.

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, verify that the DTC is set as current and that no other vehicle system DTCs exists. If other vehicle system DTCs exists, address these DTCs before proceeding with this diagnostic test.
  2. Cycle the ignition OFF then ON, clear the DTC with a scan tool and verify that the DTC does not reset as current. If the DTC resets as current, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming

Symptoms - Lighting

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) , before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
  2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following: «Exterior Lighting Systems Description and Operation»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) «Interior Lighting Systems Description and Operation»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the Lighting System. Refer to «Checking Aftermarket Accessories»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__checking-aftermarket-accessories) .
  2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

  1. «Backup Lamps Malfunction (Automatic Transmission)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Backup Lamps Malfunction (Manual Transmission)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Courtesy Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  3. «Daytime Running Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__daytime-running-lamps-malfunction)
  4. «Front Fog Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  5. «Hazard Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__hazard-lamps-malfunction)
  6. «Headlamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  7. «Interior Backlighting Malfunction (w/AN3)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Interior Backlighting Malfunction (w/o AN3)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  8. «Park, License, and/or Tail Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  9. «Stop Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  10. «Turn Signal Lamps and/or Indicators Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Backup Lamp Relay B+11
Backup Lamp Switch Signal111
Backup Lamp Relay ControlB2545 0011
Backup Lamps Control111
Backup Lamp - Left Ground1
Backup Lamp - Right Ground1
Backup Lamp Switch Ground1
1. Backup Lamps Malfunction

When the transmission is placed in the REVERSE position, the transmission control module (TCM) sends a serial data message to the body control module (BCM). The message indicates that the gear selector is in the REVERSE position. The BCM applies voltage to the backup lamp relay control circuit energizing the backup lamp relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow through the VEH BCK/UP fuse to the left and right backup lamps. The BCM also supplies voltage the to inside rearview mirror via the backup lamp relay control circuit for automatic day/night operation. Once the driver moves the gear selector out of the REVERSE position, a serial data message is sent by the TCM requesting the BCM to remove voltage from the backup lamp control circuit.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
  2. Ignition OFF, exterior lamps OFF, test for less that 5.0 ohms between the ground circuit terminal N5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect the X2 harness connector at the underhood fuse block. Disconnect the X5 harness connector at the underhood fuse block.
  4. Connect a test lamp between the control circuit terminal H8 and ground.
  5. Command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. 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.
  6. Ignition OFF, connect the X5 harness connector at the underhood fuse block. Disconnect the harness connector at the inoperative backup lamp.
  7. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal GRD and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect a test lamp between the control circuit terminal MJR and ground.
  9. Command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.
  10. If all circuits test normal, test or replace the inoperative backup lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Backup Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Backup Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  3. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Backup Lamp Relay B+11
Backup Lamp Switch Signal222
Backup Lamp Relay ControlB2545 0011
Backup Lamps Control111
Backup Lamp - Left Ground1
Backup Lamp - Right Ground1
Backup Lamp Switch Ground2
1. Backup Lamps Malfunction 2. Backup Lamp Switch Malfunction

When the transmission is placed in the REVERSE position, the backup lamp switch contacts close supplying ground to the engine control module (ECM) via the backup lamp switch signal circuit. The ECM responds by sending a serial data message to the body control module (BCM) indicating the gear selector is in the REVERSE position. The BCM applies voltage to the backup lamp relay control circuit energizing the backup lamp relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow through the VEH BCK/UP fuse to the left and right backup lamps. The BCM also supplies voltage the to inside rearview mirror via the backup lamp relay control circuit for automatic day/night operation. Once the driver moves the gear selector out of the REVERSE position, the backup lamp switch contacts open and a serial data message is sent by the ECM requesting the BCM to remove voltage from the backup lamp relay control circuit.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

  1. If the backup lamps do not turn ON and OFF when commanded, refer to «Backup Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__backup-lamps-malfunction) .
  2. If the backup lamps turn ON and OFF when commanded, refer to «Backup Lamp Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__backup-lamp-switch-malfunction) .

Backup Lamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the backup lamp switch.
  2. Ignition OFF, exterior lamps OFF, test for less that 5.0 ohms between the ground circuit terminal A and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the backup lamps are not illuminated. If the backup lamps are illuminated, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the ECM.
  4. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the backup lamps are illuminated. If the backup lamps do not illuminate, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  5. If all circuits test normal, test or replace the backup lamp switch.

Backup Lamps Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
  2. Ignition OFF, exterior lamps OFF, test for less that 5.0 ohms between the ground circuit terminal N5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect the X2 harness connector at the underhood fuse block. Disconnect the X5 harness connector at the underhood fuse block.
  4. Connect a test lamp between the control circuit terminal H8 and ground.
  5. Command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. 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.
  6. Ignition OFF, connect the X5 harness connector at the underhood fuse block. Disconnect the harness connector at the inoperative backup lamp.
  7. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal GRD and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect a test lamp between the control circuit terminal MJR and ground.
  9. Command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.
  10. If all circuits test normal, test or replace the inoperative backup lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Backup Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Backup Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  3. «Backup Lamp Switch Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/manual-trans/#manual-transmission-tremec-5-speed-m96)
  4. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM or ECM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Dome/Reading Lamp Supply Voltage11
Exterior Lamps Illumination Supply Voltage555
I/P DImming VoltageB1395 03B1395 03B1395 07
Dome Lamp Switch Signal222
Left Front Door Open Switch Signal333
Left Rear Door Open Switch Signal444
Right Front Door Open Switch Signal333
Right Rear Door Open Switch Signal444
Dome/Reading Lamp ControlB2615 00B2615 00
Dome/Reading Lamp Low Control - Driver Door1
Dome/Reading Lamp Low Control - Passenger Door1
Inadvertent Power Control555
Exterior Lamps Low Reference5
I/P Dimmer Switch Ground2
LH Vanity Mirror Courtesy Lamp Ground1
Overhead Console Courtesy Lamp Ground1
Rear Dome Lamp Ground1
RH Vanity Mirror Courtesy Lamp Ground1
Courtesy Lamps Malfunction Dome Lamp Switch Malfunction Door Open Switch Malfunction - Front Door Open Switch Malfunction - Rear Exterior Lamps Malfunction Reading/Vanity Mirror Lamps Malfunction

Voltage for the courtesy lamps is supplied from body control module (BCM), driver door switch, and passenger door switch. When a door is opened, a signal is applied to the door module. The door module then applies a message on the low speed GMLAN serial data communication circuit to the BCM to activate the courtesy lamps. The BCM then applies voltage to the courtesy lamps voltage supply circuit and the components on that circuit.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, command the Courtesy Lamps output control ON and OFF with the scan tool. The interior courtesy lamps should turn ON and OFF. If one or more of the courtesy lamps are always ON or always OFF refer to «Courtesy Lamp Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__courtesy-lamp-malfunction) .
  2. Observe the scan tool Driver Door Switch, Driver Door Open Sw. parameter while opening and closing the driver door. The reading should change between Active and Inactive. If the Driver Door Open Sw. parameter does not change between Active and Inactive, refer to «Door Open Switch Malfunction - Front w/AN3»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__door-open-switch-malfunction-front) .
  3. Observe the scan tool Passenger Door Switch, Passenger Door Open Sw. parameter while opening and closing the front passenger door. The reading should change between Active and Inactive. If the Passenger Door Open Sw. parameter does not change between Active and Inactive, refer to «Door Open Switch Malfunction - Front w/AN3»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__door-open-switch-malfunction-front) .
  4. Observe the scan tool BCM Ctsy. Lamp Actv. Reason parameter while opening and closing 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 Malfunction - Rear»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__door-open-switch-malfunction-rear) .
  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 Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__domeinterior-lamp-switch-malfunction) .
  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 Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__domeinterior-lamp-switch-malfunction) .
  7. Ignition ON, command the Puddle/Courtesy Lamp ON and OFF with a scan tool. Verify the exterior illumination lamps turn ON and OFF. If the exterior illumination lamps do not change between ON and OFF, refer to «Exterior Lamps Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__exterior-lamps-circuit-test) .
  8. Ignition ON, turn the reading lamps ON and OFF. The reading lamps should turn ON and OFF. If the reading lamps do not change between ON and OFF, refer to «Reading Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__reading-lamps-malfunction) test.
  9. Ignition On, fold down the sun visors and verify the vanity lamps illuminate. If the vanity lamps do not change between ON and OFF, refer to «Vanity Mirrors Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__vanity-mirrors-malfunction) .

Courtesy Lamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate lamp.
  2. Test for less than 5 ohms 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 appropriate bulb.

Door Open Switch Malfunction - Front w/AN3

  1. Ignition OFF, disconnect the harness connector at the inoperative door latch assembly.
  2. Test for less than 10.0 ohms between the appropriate ground circuit terminal listed below and ground. Driver door latch ground circuit terminal 5 Passenger door latch ground circuit terminal 3 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 the scan tool displays ACTIVE, test the appropriate signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the appropriate door control module. Driver door open switch signal circuit terminal 7 Passenger door open switch signal circuit terminal 2
  4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the scan tool Door Open Switch parameter is ACTIVE. Driver door open switch signal circuit terminal 7 Passenger door open switch signal circuit terminal 2 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 appropriate door control module.
  5. If all circuits test normal, replace the inoperative door latch assembly.

Door Open Switch Malfunction - Front w/o AN3

  1. Ignition OFF, disconnect the harness connector at the inoperative door latch assembly.
  2. Test for less than 10.0 ohms between the appropriate ground circuit terminal listed below and ground. w/ power door locks terminal 8 w/o power door locks terminal 6 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 the scan tool displays ACTIVE, test the appropriate signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the BCM. w/ power door locks terminal 7 w/o power door locks terminal 5
  4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the scan tool Door Open Switch parameter is ACTIVE. w/ power door locks terminal 7 to terminal 8 w/o power door locks terminal 6 to terminal 5 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, replace the inoperative door latch assembly.

Door Open Switch Malfunction - Rear

  1. Ignition OFF, disconnect the harness connector at the inoperative rear door latch assembly.
  2. Interior lamps OFF, test for less than 10.0 ohms between the appropriate ground circuit terminal listed below and ground. Left rear door latch assembly ground circuit terminal 6 Right rear door latch assembly ground circuit terminal 3 If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a test lamp illuminates between the appropriate door open switch signal circuit terminals listed below and ground. Left rear door open switch signal circuit terminal 5 Right rear door open switch signal circuit terminal 2 If the test lamp does not illuminate, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the courtesy lamps illuminate and remain illuminated. Left rear door open switch signal circuit terminal 5 Right rear door open switch signal circuit terminal 2 If the courtesy lamps do not remain illuminated, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, replace the inoperative rear door latch assembly.

Dome/Interior Lamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Test for less than 5 ohms 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 the scan tool parameter is Manual or Manual Defeat, test the appropriate signal circuit terminals 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.

Outside Rearview Mirror Illumination Malfunction

  1. Disconnect the harness connector at the appropriate exterior illumination lamp bulb.
  2. Ignition ON, verify that a test lamp illuminates between the exterior illumination lamp supply circuit terminal and ground. If the test lamp does not illuminate, test the exterior illumination lamp supply circuit for a short to ground or an open/high resistance.
  3. Connect a test lamp between the low side control circuit terminal and the exterior illumination lamp supply circuit terminal.
  4. Command the Puddle/Courtesy Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the inoperative door switch. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the inoperative door switch.
  5. If all circuits test normal, test or replace the appropriate bulb.

Reading Lamps Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the BCM.
  2. Verify a test lamp illuminates between the IS LPS fuse B+ circuit terminal 1 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Reconnect the X2 harness connector at the BCM.
  4. Disconnect the harness connector at the inoperative courtesy/reading lamp assembly.
  5. Scan tool OFF, doors CLOSED, interior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Verify a test lamp illuminates between the control circuit terminal C and ground. If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  7. Remove the IS LPS fuse and verify the test lamp turns OFF. If the test lamp remains illuminated, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, replace the inoperative courtesy/reading lamp assembly.

Vanity Mirrors Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate vanity mirror lamp.
  2. Test for less than 5 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between the inadvertent power supply circuit terminal A and ground. If the test lamp does not illuminate, test the inadvertent power supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Connect the harness connector at the vanity mirror lamp.
  5. Remove the IS LPS fuse and verify the test lamp turns OFF. If the test lamp remains illuminated, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, replace the inoperative vanity mirror.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Dome Lamp Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Front Side Door Lock Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/door-locks-anti-theft-systems/#door-lock-system-door-handles)
  3. «Rear Door Lock Replacement (Crew Cab)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/door-locks-anti-theft-systems/#door-lock-system-door-handles) or «Rear Door Lock Replacement (Extended Cab Upper)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/door-locks-anti-theft-systems/#door-lock-system-door-handles) or «Rear Door Lock Replacement (Extended Cab Lower)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/door-locks-anti-theft-systems/#door-lock-system-door-handles)
  4. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  5. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM, driver door switch, or passenger door switch replacement, programming, and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
DRL Relay B+22
Ambient Light Sensor SignalB2645 03B2645 07B2645 07
Daytime Running Lamps Control22B2600 00
Headlamp - Left Front Low Beam Control111
Headlamp - Right Front Low Beam Control111
Ambient Light Sensor GroundB2645 07
Headlamp - Left Front Ground1
Headlamp - Right Front Ground1
1. Headlamps Malfunction 2. Daytime Running Lamps Malfunction

The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The body control module (BCM) monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the DRLs ON by applying ground to the DRL relay via the DRL relay control circuit. When the BCM applies ground to the DRL relay control circuit, the DRL relay coil energizes causing the relay switch contacts to close. With the DRL relay switch contacts closed, battery voltage flows through the DRL 1 and DRL 2 fuses to the left and right LO HDLP fuses to the low beam headlamps. The DRL control circuit that supplies the low beam headlamp fuses with voltage contains a loop of wire that acts as resistance. This resistance is responsible for the low beam headlamps illuminating at a reduced intensity. Any function or condition that turns on the headlamps will cancel DRL operation.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, with a scan tool command the Low Beams ON and OFF. The low beam headlamps should turn ON and OFF when changing between the commanded states. If the low beam headlamps do not turn ON and OFF when commanded, refer to «Headlamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) .
  2. Ignition ON, park brake released, verify with a scan tool the Park Brake Switch parameter displays Released. If not the specified value, refer to «Brake Warning Indicator Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/mechanical-hydraulic/#hydraulic-brake-system) .
  3. Ignition ON, with a scan tool command the DRL ON and OFF. The low beam headlamps should turn ON and OFF when changing between the commanded states. If the low beam headlamps do not turn ON and OFF when commanded, refer to «Daytime Running Lamps Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) . If the low beam headlamps turn ON and OFF when commanded, refer to «Ambient Light Sensor Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__ambient-light-sensor-malfunction) .

Daytime Running Lamps Malfunction

  1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
  2. Connect a test lamp between the control circuit terminal H4 and B+.
  3. Command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Ignition OFF, connect the X4 harness connector at the underhood fuse block.
  5. Remove the DRL 2 fuse from the underhood fuse block.
  6. Connect a test lamp between the relay control circuit of the DRL 2 fuse and ground.
  7. Command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit terminal A3 X1 for a short to voltage. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF, test the control circuit terminal A3 X1 for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  8. If all circuits test normal, replace the underhood fuse block.

Ambient Light Sensor Malfunction

  1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
  2. Ignition OFF, scan tool OFF, doors CLOSED, test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground. Terminal B - with C67/C42 Terminal C - with CJ2 If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.5 volts. If less than the specified range, test the appropriate signal circuit terminal listed below for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. Terminal A - with C67/C42 Terminal D - with CJ2
  4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 volts. Terminal A - with C67/C42 Terminal D - with CJ2 If greater than the specified range, 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, replace the ambient light sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Ambient Light Sensor Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  3. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Fog Lamp Relay B+11
Fog Lamp Switch Signal222
Fog Lamp Relay Control11B2530 00
Fog Lamp Control111
Fog Lamp - LF Ground1
Fog Lamp - RF Ground1
Fog Lamp Switch Ground2
1. Fog Lamps Malfunction 2. Fog Lamp Switch Malfunction

The fog lamp relay is supplied with battery voltage at all times. The fog lamp switch signal circuit is grounded momentarily by pressing the fog lamp switch. The body control module (BCM) energizes the fog lamp relay by applying ground to the fog lamp relay control circuit. When the fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the FOG LAMP fuse to the fog lamp supply voltage circuit which illuminates the fog lamps.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool Front Fog Lamp Switch parameter while activating the fog lamp switch. The reading should change between Active and Inactive.

  1. If the reading does not change between the commanded states, refer to «Fog Lamp Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__fog-lamp-switch-malfunction) .

Fog Lamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 8. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Front Fog Lamp Switch parameter is Inactive. If not the specified value, test the signal circuit terminal 10 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal 10 and the ground circuit terminal 8. Verify the scan tool Front Fog Lamp Switch parameter is Active. 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 headlamp switch.

Fog Lamps Malfunction

  1. Ignition OFF, disconnect the fog lamp relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Ignition OFF, disconnect the harness connector at the inoperative fog lamp.
  6. Test for less than 5.0 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the inoperative fog lamp.
  8. Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the fog lamps are activated. If the fog lamps do not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the inoperative fog lamp.
  9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  10. Command the Fog Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  11. If all circuits test normal, test or replace the fog lamp relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Fog Lamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__fog-lamp-switch-replacement-with-rpo) or «Fog Lamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__fog-lamp-switch-replacement-without-rpo)
  2. «Front Fog Lamp Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Front Fog Lamp Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  3. «Relay Replacement (Attached to Wire Harness)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  4. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Hazard Switch Signal111
Turn Signal/Multifunction Switch Ground1
1. Hazard Lamps Malfunction

The hazard flashers may be activated in any power mode. The hazard switch is located on the turn signal/multifunction switch and is permanently grounded through ground G201. When the hazard switch is placed in the ON position, ground is applied through the hazard switch signal circuit to the body control module (BCM). The BCM supplies battery voltage to all four turn signal lamps in an ON and OFF duty cycle. When the hazard switch is activated, the BCM sends a serial data message to the instrument panel cluster (IPC) requesting both turn signal indicators to be cycled ON and OFF.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Hazard Lamps Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal C. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Hazard Lamp Switch parameter is Inactive. If not the specified value, test the signal circuit terminal G for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal G and ground. Verify the scan tool Hazard Lamp Switch parameter is Active. 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 turn signal/multifunction switch.

Hazard Lamp Indicators Malfunction

Ignition ON, with a scan tool perform the Lamp Test for the instrument panel cluster (IPC) and observe both turn signal indicators.

  1. If both turn signal indicators illuminate during the test, replace the BCM.
  2. If both turn signal indicators do not illuminate during the test or remain illuminated at all times, replace the IPC.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Turn Signal Multifunction Switch Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/steering-column-switches/#steering-wheel-and-steering-column)
  2. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM or IPC replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
HDLP LO/HID Relay B+222
HI Beam Relay B+333
Flash to Pass Switch Signal444
Headlamp Switch Headlamps ON SignalB257A 0011
Headlamp Switch Headlamps OFF SignalB257A 0011
Headlamp Switch High Beam Signal444
Headlamp High Beam Relay Control33B2580 00
Headlamp Low Beam Relay Control22B2575 00
Headlamp and Panel Dimmer Switch Ground1
LF Headlamp Ground2
RF Headlamp Ground2
Turn Signal/Multifunction Switch Ground1
1. Headlamp Switch Malfunction 2. Headlamps Malfunction - Low Beam 3. Headlamps Malfunction - High Beam 4. Headlamp Dimmer Switch Malfunction

With the headlamp switch in the ON position, the headlamp switch headlamp ON signal circuit is grounded through the headlamp switch at ground G201. In response to this input, the body control module (BCM) provides ground to either the headlamp low beam relay control circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay coil is supplied with ground. The BCM supplies ground to the relay coil circuits, if the headlamps are necessary. The underhood fuse block supplies battery voltage to the relay coil and switch circuits. The low beam headlamps operate when the BCM grounds the relay coil control circuit to the relay coil of the low beam headlamp relay. This energizes the low beam relay causing the switch contacts to close. With the switch contacts closed, battery voltage is applied to the LT-LO HDLP and RT-LO HDLP beam fuses through to the left and right low beam headlamps. When the headlamp high beam relay coil is energized, current flows through the LT-HI HEADLAMP and the RT-HI HEADLAMP fuses to the high beam headlamps. With the headlamp dimmer switch in the high beam position the BCM sends a serial data message to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Headlamp Switch parameter while turning the headlamp switch ON and OFF. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamp-switch-malfunction) .
  2. Observe the scan tool Flash to Pass Switch parameter while applying and releasing the flash to pass switch. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Dimmer Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamp-dimmer-switch-malfunction) .
  3. Observe the scan tool High Beam Select Switch parameter while applying and releasing the high beam select switch. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Dimmer Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamp-dimmer-switch-malfunction) .
  4. Observe the scan tool Auto Hdlp. Disable Sw. parameter while applying and releasing the automatic lamp control disable switch. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamp-switch-malfunction) .
  5. Command the Low Beams ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when commanded. If the low beam headlamps do not turn ON and OFF when commanded, refer to «Headlamps Malfunction - Low Beam»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamps-malfunction-low-beam) .
  6. Command the High Beams ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when commanded. If the high beam headlamps do not turn ON and OFF when commanded, refer to «Headlamps Malfunction - High Beam»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamps-malfunction-high-beam) .

Headlamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 8. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Headlamp Switch parameter is Inactive. If not the specified value, test the signal circuit terminal 1 for short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Auto Hdlp. Disable Sw. parameter is Inactive. If not the specified value, test the signal circuit terminal 3 for short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 1 and ground. Verify the scan tool Headlamp Switch parameter is Active. 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. Install a 3A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Auto Hdlp. Disable Sw. parameter is Active. 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.
  7. If all circuits test normal, test or replace the headlamp switch.

Headlamp Dimmer Switch Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the turn signal/multifunction switch.
  2. Verify that a test lamp illuminates between B+ and the ground circuit terminal D. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Verify the scan tool High Beam Select switch parameter is Inactive. If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Flash to Pass Switch parameter is Inactive. If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal E and ground. Verify the scan tool High Beam Select Switch parameter is Active. 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. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Flash to Pass Switch parameter is Active. 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.
  7. If all circuits test normal, test or replace the signal/multifunction switch.

Headlamps Malfunction - Low Beam

  1. Ignition OFF, disconnect the low beam relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Ignition OFF, disconnect the harness connector at the inoperative low beam headlamp.
  6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the inoperative low beam headlamp.
  8. Connect a 40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the low beam headlamps are activated. If the low beam headlamps do not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the inoperative low beam headlamp.
  9. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
  10. Command the Low Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  11. If all circuits test normal, test or replace the low beam relay.

Headlamps Malfunction - High Beam

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Connect a test lamp between the control circuit terminal C3 and B+.
  3. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM.
  4. Ignition OFF, connect the X4 harness connector at the BCM. Disconnect the harness connector at the inoperative high beam headlamp.
  5. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the control circuit terminal A and ground.
  7. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.
  8. If all circuits test normal, replace the inoperative high beam headlamp.

High Beam Indicator Malfunction

Ignition ON, with a scan tool perform the Lamp Test for the instrument panel cluster (IPC) and observe the high beam indicator.

  1. If the high beam indicator does not illuminate during the test or remains illuminated at all times, replace the IPC.
  2. If the high beam indicator illuminates during the test, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Headlamp Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Replacement (GMC HD)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamp-replacement-gmc-hd) or «Headlamp Replacement (HD Diesel)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__headlamp-replacement-hd-diesel)
  3. «Headlamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  4. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  5. «Turn Signal Multifunction Switch Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/steering-column-switches/#steering-wheel-and-steering-column)
  6. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM or IPC replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
IS LPS fuse B+B1395 03B1395 03
I/P Dimmer Switch SignalB1395 0311
I/P Lamps Dimmer Switch SignalB2652 0022
I/P Dimming Voltage ReferenceB1395 0311
Indicator Dimming ControlB2625 0033
LED Backlight Dimming ControlB2610 0033
I/P Dimmer Switch Ground1
1. Dimmer Switch Malfunction 2. Interior Backlighting Malfunction - Incandescent 3. Interior Backlighting Malfunction - LED

When the ignition switch is turned to the RUN position, the radio VF display turns ON at maximum brightness. When the park lamps are ON, all incandescent and LED back lighting turn ON at the dimming level indicated by the instrument panel (I/P) dimmer switch. At the same time all VF displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the body control module (BCM). When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all incandescent back lighting lamps are provided with a specific voltage. When the I/P dimmer switch is moved from MIN to MAX, all VF displays, as well as all incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the driver door switch while commanding the Driver Door Switch Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or remains always ON, replace the driver door lock and side window switch.
  2. Ignition ON, observe the driver memory/heated seat switch while commanding the Driver Door Switch Non-Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or remains always ON, refer to «Interior Backlighting Malfunction - Incandescent»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__interior-backlighting-malfunction-incandescent) .
  3. Ignition ON, observe the passenger door switch while commanding the Passenger Door Switch Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or always remains ON, replace the passenger door lock and side window switch.
  4. Ignition ON, observe the passenger heated seat switch while commanding the Passenger Door Switch Non-Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or remains always ON, refer to «Interior Backlighting Malfunction - Incandescent»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__interior-backlighting-malfunction-incandescent) .
  5. Ignition ON, observe the scan tool BCM Dimming Control Signal parameter while operating the dimmer switch from high to low. The reading should change from a high percent to a low percent as the switch is rotated. If the reading does not change, refer to «LED Dimming Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__led-dimming-circuit-test) .
  1. If the scan tool dimmer control operates normal, refer to the «Interior Backlighting Malfunction - Incandescent»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__interior-backlighting-malfunction-incandescent) or the «LED Dimming Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__led-dimming-circuit-test) .

Interior Backlighting Malfunction - Incandescent

  1. Ignition OFF, disconnect the X3 harness connector at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the IS LPS fuse B+ circuit terminal 2 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Ignition OFF, reconnect the X3 harness connector at the BCM.
  4. Disconnect the harness connector at the component with the inoperative incandescent backlighting.
  5. Ignition OFF, scan tool OFF, interior lamps OFF, doors CLOSED, test for less than 5 ohms between the ground circuit and ground. If greater than the specified value, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the control circuit and ground.
  7. Command the Incandescent Dimming Control ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. 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. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, test or replace the component with the inoperative incandescent backlighting.

Dimmer Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
  2. 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 B+ 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 and panel dimmer switch.

Interior Backlighting Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate component.
  2. Verify that a test lamp illuminates between the listed ground circuit terminal and B+. Rear Window Switch terminal F Headlamp and Panel Dimmer Switch terminal 8 Transfer Case Shift Control Switch terminal 6 Sunroof Switch terminal 5 Roof Beacon Switch terminal 1 Sliding Rear Window Switch terminal D Garage Door Opener Switch terminal 3 Door Lock Switch terminal B Window Switch terminal F Outside Rearview Mirror Switch terminal G If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the listed backlighting control circuit terminal and ground. Rear window switch terminal B Headlamp switch terminal 7 Transfer case control switch terminal 5 Sunroof switch terminal 3 Roof beacon switch terminal 2 Sliding rear window switch terminal E Garage door opener switch terminal 2 Door Lock Switch terminal A Window Switch terminal B Outside Rearview Mirror Switch terminal E
  4. Command the Incandescent Dimming Test ON with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states. 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. If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the appropriate component.

LED Dimming Circuit Test

  1. Ignition OFF, disconnect the harness connector at the appropriate component.
  2. Verify that a test lamp illuminates between the listed ground circuit terminal and battery voltage. Right steering wheel switch terminal 1 Left steering wheel switch terminal 8 DIC switch terminal 5 Manual HVAC control module terminal 10 X2 Multifunction accessory switch terminal 3 If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the listed LED dimming control circuit terminal and ground. Right steering wheel switch terminal 2 Left steering wheel switch terminal 6 Power take off switch terminal 6 Trailer brake controller switch terminal 7 IPC terminal 8 Radio terminal 7 X1 DIC switch terminal 4 Manual HVAC control module terminal 1 X2 Multifunction accessory switch terminal 4
  4. Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states. If the test lamp is always off, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the appropriate component.

Front Door Switch Backlighting Circuit Test

  1. Ignition OFF, disconnect the harness connector X4 at the door lock and side window switch.
  2. Connect a 3A fused jumper wire between the low reference circuit terminal 4 and ground.
  3. Connect a test lamp between the backlight supply voltage circuit terminal 13 and B+. The heated seat switch backlighting should illuminate. If the switch backlighting does not illuminate, replace the heated seat switch.
  4. If the switch backlighting tests normal, replace the door lock and side window switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Front Seat Heater Switch Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/seats/#seat-heating-system-seat-cooling-system)
  2. «Steering Wheel Control Switch Assembly Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/memory-modules/#configurable-customer-control-system)
  3. «Driver Information Display Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages) or «Driver Information Display Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages)
  4. «Accessory Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages) or «Accessory Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages)
  5. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  6. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM, door lock and side window switch, IPC, radio, HVAC control module, and rear seat audio controller replacement, programming, and setup.
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
IS LPS Fuse B+ SupplyB1395 03B1395 03
I/P Dimmer Switch SignalB1395 0311
I/P Lamps Dimmer Switch SignalB2652 0022
I/P Dimming Voltage ReferenceB1395 0311
Indicator Dimming ControlB2625 0033
LED Backlight Dimming ControlB2610 0033
I/P Dimmer Switch Ground1
1. Dimmer Switch Malfunction 2. Interior Backlighting Malfunction - Incandescent 3. Interior Backlighting Malfunction - LED

When the ignition switch is turned to the RUN position, the radio VF display turns ON at maximum brightness. When the park lamps are ON, all incandescent and LED back lighting turn ON at the dimming level indicated by the instrument panel (I/P) dimmer switch. At the same time all VF displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the body control module (BCM). When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all incandescent back lighting lamps are provided with a specific voltage. When the I/P dimmer switch is moved from MIN to MAX, all VF displays, as well as all incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool BCM Dimming Control Signal parameter while operating the dimmer switch from high to low. The reading should change from a high percent to a low percent as the switch is rotated.

  1. If the reading does not change, refer to «Dimmer Switch Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__dimmer-switch-circuit-test) .
  1. If the scan tool dimmer control operates normal, refer to the «Interior Backlighting Malfunction - LED»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__interior-backlighting-malfunction-led) .

Dimmer Switch Circuit Test

  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 B+ 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.

Interior Backlighting Malfunction - LED

  1. Ignition OFF, disconnect the X3 harness connector at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the IS LPS fuse B+ circuit terminal 2 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Ignition OFF, reconnect the X3 harness connector at the BCM.
  4. Disconnect the harness connector at the component with the inoperative LED backlighting.
  5. Ignition OFF, scan tool OFF, interior lamps OFF, doors CLOSED, test for less than 5 ohms between the ground circuit and ground. If greater than the specified value, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the control circuit and ground.
  7. Command the LED Dimming Control ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. 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. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, test or replace the component with the inoperative LED backlighting.

Interior Backlighting Circuit Test

  1. Ignition OFF, disconnect the harness connector at the affected component.
  2. Ignition OFF, verify that a test lamp illuminates between the listed ground circuit terminal and battery voltage. Passenger window switch terminal F Headlamp switch terminal 8 Transfer case control switch terminal 6 Sunroof switch terminal 5 Door lock switch terminal B Roof beacon switch terminal 1 Sliding rear window switch terminal D Garage door opener switch terminal 3 Outside rear view mirror switch terminal G Driver window switch terminal A X2 If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the listed backlighting control circuit terminal and ground. Passenger window switch terminal B Headlamp switch terminal 7 Transfer case control switch terminal 5 Sunroof switch terminal 3 Door lock switch terminal A Roof beacon switch terminal 2 Sliding rear window switch terminal E Garage door opener switch terminal 2 Outside rear view mirror switch terminal E Driver window switch terminal 1 X1
  4. Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states. If the test lamp is always off, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the affected component.
  1. Ignition OFF, disconnect the harness connector at the affected component.
  2. Ignition OFF, verify that a test lamp illuminates between the listed ground circuit terminal and battery voltage. Right steering wheel switch terminal 1 Left steering wheel switch terminal 8 DIC switch terminal 5 Manual HVAC control module terminal 10 X2 Multifunction accessory switch terminal 3 If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the listed LED dimming control circuit terminal and ground. Right steering wheel switch terminal 2 Left steering wheel switch terminal 6 Power take off switch terminal 6 Trailer brake controller switch terminal 7 IPC terminal 8 Radio terminal 7 X1 DIC switch terminal 4 Manual HVAC control module terminal 1 X2 Multifunction accessory switch terminal 4
  4. Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states. If the test lamp is always off, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the affected component.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Front Seat Heater Switch Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/seats/#seat-heating-system-seat-cooling-system)
  2. «Steering Wheel Control Switch Assembly Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/memory-modules/#configurable-customer-control-system)
  3. «Driver Information Display Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages) or «Driver Information Display Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages)
  4. «Accessory Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages) or «Accessory Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages)
  5. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  6. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM, IPC, radio, and HVAC control module replacement, programming, and setup.
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
PARK LAMP Relay Control11B2585 00
Park Lamp Switch ON Signal222
License Lamp Supply Voltage111
Park Lamp Voltage Supply111
License Lamp Ground1
Park Lamps - LF Ground1
Park Lamps - RF Ground1
Tail/Stop and Turn Signal Lamps - LR Ground1
Tail/Stop and Turn Signal Lamps - RR Ground1
Turn Signal/Multifunction Switch Ground2
Park, License, and/or Tail Lamps Malfunction Park Lamp Switch Malfunction

B+ is applied at all times to both the coil and switch sides of the PARK LAMP Relay located in the underhood fuse block. The turn signal/multifunction switch is supplied with ground at G201 at all times. When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the park lamp signal circuit to the body control module (BCM). The BCM responds by applying ground to the park lamp relay control circuit. This energizes the park lamp relay coil causing the relay switch contacts to close allowing B+ to flow through the LT PRK, RT PRK, and TRLR PRK fuses, to all of the park, tail, license, and marker lamps.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool parklamp switch parameter while cycling the headlamp switch between the park and off positions. The parameter should cycle between active and inactive. If the parameter does not cycle between the specified values, refer to «Park Lamp Switch Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__park-lamp-switch-circuit-test) .
  2. Connect a test lamp between the relay side of a park lamp fuse and ground.
  3. Command the parking lamps on and off with a scan tool. Verify that the test lamp turns on and off while switching between the commanded states. If the test lamp does not turn on and off while changing between the commanded states, refer to the «Park Lamp Relay Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__park-lamp-relay-circuit-test) .
  4. If any of the park, marker, license, or tail lamps do not turn on and off, refer to «Exterior Lamps Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__exterior-lamps-circuit-test) .

Park Lamp Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Test for less than 1.0 ohm 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 parklamp switch parameter is inactive. If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool BCM parklamp switch parameter is active. If not the specified value, test the signal circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the headlamp switch.

Park Lamp Relay Circuit Test

  1. Ignition OFF, disconnect the PARK LAMP Relay.
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, replace the underhood fuse block.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 86 and ground. If the test lamp does not illuminate, replace the underhood fuse block.
  4. Connect a test lamp between the relay control circuit terminal 85 and the B+ circuit terminal 86.
  5. 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. 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.
  6. If all circuits test normal, test or replace the PARK LAMP Relay.

Exterior Lamps Circuit Test

  1. Ignition OFF, disconnect the harness connector at the appropriate park, marker, license, or tail lamp.
  2. Verify that a test lamp illuminates when connected between B+ and the listed ground circuit terminal. Front park lamp terminal G Tail lamp terminal GRD Marker and clearance lamps terminal A License lamp terminal B If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, connect a test lamp between the listed control circuit terminal and ground. Front park lamp terminal MAJ Tail lamp terminal MNR Marker and clearance lamps terminal B License lamp terminal A
  4. 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. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control 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 appropriate lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Parking and Turn Signal Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Parking and Turn Signal Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Rear License Plate Lamp Replacement (Silverado)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Rear License Plate Lamp Replacement (VF7)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  3. «Tail Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Tail Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  4. «Headlamp Switch Replacement (with RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Headlamp Switch Replacement (without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  5. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, programming, and setup.
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

When the driver presses the brake pedal, the switch contacts open and B+ is interrupted to the BCM. The BCM then supplies voltage to both the turn/stop lamp supply voltage circuit and trailer rear turn/stop lamp supply voltage circuits. The BCM also supplies a control voltage to the CHMSL relay energizing the relay and illuminating the CHMSL.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool BCM Stop Lamp Switch Status parameter while pressing and releasing the brake pedal. The reading should change between 1 count and approximately 1023 counts. If not the specified value, refer to the «Stop Lamp Switch Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__stop-lamp-switch-circuit-test) .
  2. Ignition ON, observe the scan tool TCM Brake Switch parameter while pressing and releasing the brake pedal. The reading should change between Pressed and Released. If not the specified value, refer to the «Stop Lamp Switch Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__stop-lamp-switch-circuit-test) .
  3. Ignition ON, observe the left, and right stop lamps while pressing and releasing the brake pedal. The stop lamps should turn on and off. If the left and or right stop lamps are always on or inoperative, refer to the «Stop Lamp Switch Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__stop-lamp-switch-circuit-test) .
  4. Connect a test lamp between the relay side of the CHMSL fuse and ground.
  5. Verify that the test lamp turns on and off while pressing and releasing the brake pedal. If the test lamp does not turn on and off while changing between the commanded states, refer to the «CHMSL Relay Control Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__chmsl-relay-control-circuit-test) .
  6. If the center high mount stop lamp is always on or inoperative refer to the «CHMSL Relay Control Circuit Test»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__chmsl-relay-control-circuit-test) .

Stop Lamp Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
  2. Ignition ON, test for B+ between the 12-volt reference circuit terminal C and ground. If less than the specified range, test the 12-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  3. Verify the scan tool BCM Stop Lamp Switch Status parameter is approximately 1023 counts. If not the specified value, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal D and the 12-volt reference circuit terminal C. Verify the scan tool Stop Lamp Switch Status parameter is 1 count. If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the stop lamp switch.

Brake Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
  2. Ignition ON, test for B+ between the ignition supply circuit terminal B and ground. If less than the specified range, test the ignition supply circuit for a short to ground or an open/high resistance.
  3. Verify the scan tool TCM Brake Switch parameter is Released. If not the specified value, test the signal circuit terminal A for a short to voltage.
  4. Install a 3A fused jumper wire between the signal circuit terminal B and the ignition supply circuit terminal A. Verify the scan tool Brake Switch parameter is Applied. If not the specified value, test the signal circuit for an open/high resistance.
  5. If all circuits test normal, test or replace the stop lamp switch.

Stop Lamp Circuit Test

  1. Ignition OFF, disconnect the harnes connector X4 at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the terminals listed below and ground. Terminal 1 Terminal 2 Terminal 4 If the test lamp does not illuminate, test the B+ circuit for an open/high resistance or short to ground.
  3. Connect the harness connector X4 at the BCM.
  4. Ignition OFF, disconnect the harness connector at the appropriate stop lamp.
  5. Test for less than 1 ohm between the ground circuit terminal GRD and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the stop lamp control circuit terminal MJR and ground.
  7. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.
  8. If all circuits test normal, test or replace the appropriate stop lamp.

CHMSL Relay Control Circuit Test

  1. Ignition OFF, disconnect the harness connector X5 at the BCM.
  2. Ignition ON, verify the center high mount stop lamp is not on. If the center high mount stop lamp is on, test the CHMSL relay control circuit terminal 5 for a short to voltage. If the circuit tests normal replace the underhood fuse block.
  3. Install a 10A fused jumper wire between the CHMSL relay control circuit terminal 5 and B+. Verify the center high mount stop lamp is on. If the center high mount stop lamp is not on or the fuse in the jumper wire opens, test the CHMSL relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the underhood fuse block.
  4. If all circuits test normal, replace the BCM.

CHMSL Circuit Test

  1. Ignition OFF, disconnect the harnes connector at the center high mount stop lamp.
  2. Test for less than 1 ohm between the ground circuit terminal 1 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 A and the ground circuit terminal B.
  4. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.
  5. If all circuits test normal, test or replace the center high mounted stop lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Stop Lamp Switch Replacement (With Adjustable Pedals)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Stop Lamp Switch Replacement (Without Adjustable Pedals)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «High Mount Stop Lamp Replacement (Extended and Crew Cab)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «High Mount Stop Lamp Replacement (Regular Cab)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  3. «Tail Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Tail Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  4. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, programming, and setup.
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
CTSY Fuse B+11
RT STOP TRN Fuse B+11
LT STOP TRN Fuse B+11
Hazard Switch Signal222
Left Turn Signal Switch Signal333
Right Turn Signal Switch Signal333
Hazard Switch Ground2
Stop/Tail/Turn Signal Lamp - LR Ground1
Stop/Tail/Turn Signal Lamp - RR Ground1
Turn Signal/Multifunction Switch Ground3
Turn Signal Lamp - LF Ground1
Turn Signal Lamp - RF Ground11
1. Turn Signal Lamps and/or Indicators Malfunction 2. Hazard Lamps Malfunction 3. Turn Signal Switch Malfunction

Ground is applied at all times at G201 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM then applies a pulsating voltage to the front and rear turn signal lamps through their respective control circuits.

An open CTSY fuse located in the I/P fuse block will affect the operation of the right front turn signal only.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool Right and Left Turn Signal Switch parameters while cycling the turn signal switch between the left and right positions. The parameters should change between Active and Inactive.

  1. If the parameters do not change between the commanded states, refer to «Turn Signal Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__turn-signal-switch-malfunction) .
  2. If the parameters change between the commanded states, refer to «Turn Signal Switch Malfunction»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems__turn-signal-switch-malfunction) .

Turn Signal Switch Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal F. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Left Turn Signal Switch parameter is Inactive. If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Right Turn Signal Switch parameter is Inactive. If not the specified value, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal E and ground. Verify the scan tool Left Turn Signal Switch parameter is Active. 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. Install a 3A fused jumper wire between the signal circuit terminal D and ground. Verify the scan tool Right Turn Signal Switch parameter is Active. 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.
  7. If all circuits test normal, test or replace the turn signal/multifunction switch.

Turn Signal Lamps Malfunction

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Verify that a test lamp illuminates between the B+ circuit terminal 1 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 2 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 3 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  5. Ignition OFF, connect the X4 harness connector at the BCM.
  6. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
  7. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal GRD and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect a test lamp between the control circuit terminal MJR and ground.
  9. Command the appropriate turn signal lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. 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.
  10. If all circuits test normal, replace the appropriate turn signal lamp.

Turn Signal Indicators Malfunction

Ignition ON, with a scan tool perform the Lamp Test for the instrument panel cluster (IPC) and observe the turn signal lamp indicators.

  1. If the turn signal lamp indicators illuminate during the test, replace the BCM.
  2. If the turn signal lamp indicators do not illuminate during the test or remain illuminated at all times, replace the IPC.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Parking and Turn Signal Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Parking and Turn Signal Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  2. «Tail Lamp Bulb Replacement (Chevrolet)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems) or «Tail Lamp Bulb Replacement (GMC)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/exterior-lights/#lighting-systems)
  3. «Turn Signal Multifunction Switch Replacement»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/steering-column-switches/#steering-wheel-and-steering-column)
  4. «Control Module References»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM or IPC replacement, setup, and programming

Removal Procedure

  1. Apply the park brake.
  2. Remove the driver knee bolster. Refer to «Knee Bolster Replacement (With RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-trim-and-console-trim) or «Knee Bolster Replacement (Without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-trim-and-console-trim) .
  3. Disconnect the stoplamp switch electrical connector.
  4. Remove the power vacuum brake booster pushrod retainer bolt (1).
  5. Remove the power vacuum brake booster pushrod retainer (1).
  6. Slide the power vacuum brake booster pushrod off of the brake pedal pin and remove the stoplamp switch (1).

Installation Procedure

  1. Install the stoplamp switch (1) to the power vacuum brake booster pushrod.
  2. Install the power vacuum brake booster pushrod with the stoplamp switch to the brake pedal pin.
  3. Install the power vacuum brake booster pushrod retainer (1).
  4. Rotate the pushrod retainer 360 degrees to verify the retainer is fully engaged in the groove on the brake pedal pin.
  5. Install the power vacuum brake booster pushrod retainer bolt (1) and tighten to 10 N.m (89 lb in).
  6. Connect the stoplamp switch electrical connector.
  7. Install the driver knee bolster. Refer to «Knee Bolster Replacement (With RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-trim-and-console-trim) or «Knee Bolster Replacement (Without RPO SLT)»(/chevrolet/cab-chassis-silverado-3500-hd/2008-2011/remont/gauges-instrument-panels/#instrument-panel-trim-and-console-trim) .

Scheme 22

Scheme 22: Stop Lamp Switch Replacement (Without Adjustable Pedals)
Scheme 22: Stop Lamp Switch Replacement (Without Adjustable Pedals)
CalloutComponent Name
Preliminary Procedures Apply the park brake. Remove the driver knee bolster. Refer to Knee Bolster Replacement (With RPO SLT) or Knee Bolster Replacement (Without RPO SLT) . Disconnect the stoplamp switch electrical connector.
1Power Vacuum Brake Booster Pushrod Retainer Bolt CAUTION: Refer to Fastener Caution . Tighten: 10 N.m (89 lb in)
2Power Vacuum Brake Booster Pushrod Retainer Procedure: Rotate the pushrod retainer 360 degrees to verify the retainer is fully engaged in the groove on the brake pedal pin.
3Stoplamp Switch
CAUTION
Refer to Fastener Caution .

Scheme 23

Scheme 23: Headlamp Switch Replacement (with RPO SLT)
Scheme 23: Headlamp Switch Replacement (with RPO SLT)
CalloutComponent Name
1Headlamp Switch Trim Plate Assembly Refer to Headlamp Switch Bezel Replacement (with RPO SLT) .
2Headlamp and I/P Lamp Dimmer and Dome Lamp Switch Assembly

Scheme 24

Scheme 24: Headlamp Switch Replacement (without RPO SLT)
Scheme 24: Headlamp Switch Replacement (without RPO SLT)
CalloutComponent Name
1Instrument Panel Trim Plate Assembly Refer to Instrument Panel Trim Plate Replacement (Without RPO SLT)
2Headlamp and I/P Lamp Dimmer and Dome Lamp Switch Assembly

Fog Lamp Switch Replacement (with RPO SLT)

CalloutComponent Name
1Headlamp Switch Trim Plate Assembly Refer to Headlamp Switch Bezel Replacement (with RPO SLT) .
2Headlamp and I/P Lamp Dimmer and Dome Lamp Switch Assembly Tip: Fog lamp switch is an integral part of the headlamp switch and the unit must therefore be replaced in whole.

Fog Lamp Switch Replacement (without RPO SLT)

CalloutComponent Name
1Instrument Panel Trim Plate Assembly Refer to Instrument Panel Trim Plate Replacement (Without RPO SLT) .
2Headlamp and I/P Lamp Dimmer and Dome Lamp Switch Assembly Tip: Fog lamp switch is an integral part of the headlamp switch and the unit must therefore be replaced in whole.

Scheme 25

Scheme 25: Ambient Light Sensor Replacement
Scheme 25: Ambient Light Sensor Replacement
CalloutComponent Name
1Instrument Panel Trim Panel Refer to Instrument Panel Upper Trim Panel with Windshield Defroster Nozzle Grille Replacement (with RPO SLT) or Instrument Panel Upper Trim Panel with Windshield Defroster Nozzle Grille Replacement (without RPO SLT) .
2Headlamp Auto Control Ambient Light Sensor Assembly Tip: Twist and pull down to remove. Disconnect electrical connector.

Scheme 26

Scheme 26: Outside Rearview Mirror Courtesy Lamp Replacement
Scheme 26: Outside Rearview Mirror Courtesy Lamp Replacement
CalloutComponent Name
Fastener Tightening Specifications: Refer to Fastener Tightening Specifications .
1Exterior Courtesy Lamp Assembly Tip: Use a flat-bladed tool to pry off assembly starting at end closest to door. Tilt assembly end and pull down to release. Disconnect electrical connector.
2Exterior Courtesy Lamp Socket Tip: Twist and pull to release.
3Exterior Courtesy Lamp Bulb

Scheme 27

Scheme 27: Dome Lamp Replacement
Scheme 27: Dome Lamp Replacement
CalloutComponent Name
1Dome Lamp Lens Tip: Using a flat-bladed tool pry down on right side of lens to avoid damaging tab.
2Dome Lamp Housing Tip: Disconnect electrical connector.

Scheme 28

Scheme 28: Headlamp Replacement (Chevrolet)
Scheme 28: Headlamp Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedure Remove the upper radiator grille. Refer to Radiator Grille Replacement (Chevrolet) or Radiator Grille Replacement (GMC) . Behind the headlamp at the top of the front bumper access the lower inside hidden headlamp bolt. Loosen the bolt only, do not remove, the lower outside hidden headlamp bolt.
1Headlamp Screws (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 6 N.m (53 lb in)
2Headlamp Screw (Hidden) Tighten: 6 N.m (53 lb in)
3Headlamp Housing Support Procedure Apply masking tape to the front bumper end caps to protect the painted surface. For the right side lamp assembly only, disengage the upper retainer for the radiator air baffle. Release the headlamp from the support tab, rotate the lamp assembly towards the center of the vehicle. Disengage the headlamp electrical connector from the forward lamp harness.
CAUTION
Refer to Fastener Caution .

Headlamp Replacement (GMC HD)

CalloutComponent Name
Preliminary Procedure Loosen only, do not remove, the lower outside hidden headlamp bolt (2). Depress the housing support tab with a flat-bladed tool downward in order to release the headlamp assembly from the support. Pull the lamp assembly slightly forward to access the electrical connection. Disconnect the forward lamp harness main electrical connector from the headlamp harness.
1Headlamp Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 6 N.m (53 lb in)
2Headlamp Screw (Hidden) Tighten: 6 N.m (53 lb in)
3Headlamp Housing Support
CAUTION
Refer to Fastener Caution .

Headlamp Replacement (HD Diesel)

CalloutComponent Name
Preliminary Procedure Lower the front bumper impact bar. Refer to Front Bumper Impact Bar Replacement (Chevrolet) or Front Bumper Impact Bar Replacement (GMC) . Loosen only, do not remove, the lower outside hidden headlamp bolt (2). Depress the housing support tab with a flat-bladed tool downward in order to release the headlamp assembly from the support. Pull the lamp assembly slightly forward to access the electrical connection. Disconnect the forward lamp harness main electrical connector from the headlamp harness.
1Headlamp Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 6 N.m (53 lb in)
2Headlamp Screw (Hidden) Tighten: 6 N.m (53 lb in)
3Headlamp Housing Support
CAUTION
Refer to Fastener Caution .

Scheme 29

Scheme 29: Headlamp Bulb Replacement (Chevrolet)
Scheme 29: Headlamp Bulb Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedure: Remove either the LF or RF headlamp Assembly. Refer to Headlamp Replacement (Chevrolet) or Headlamp Replacement (GMC HD) or Headlamp Replacement (HD Diesel) .
1Headlamp Bulb (Hi) WARNING: Refer to Halogen Bulb Warning . Tip: Disconnect the headlamp bulb electrical connector and turn the bulb assembly a quarter counterclockwise to remove.
2Headlamp Bulb (Lo) Tip: Disconnect the headlamp bulb electrical connector and turn the bulb assembly a quarter counterclockwise to remove.
WARNING
Refer to Halogen Bulb Warning .

Scheme 30

Scheme 30: Headlamp Bulb Replacement (GMC)
Scheme 30: Headlamp Bulb Replacement (GMC)
CalloutComponent Name
Preliminary Procedure: Remove either the LF or RF headlamp assembly. Refer to Headlamp Replacement (Chevrolet) or Headlamp Replacement (GMC HD) or Headlamp Replacement (HD Diesel) .
1Headlamp Bulb (Hi) WARNING: Refer to Halogen Bulb Warning . Tip: Rotate the bulb socket a quarter turn counterclockwise and remove the bulb from the headlamp.
2Headlamp Bulb (Lo) Tip: Rotate the bulb socket a quarter turn counterclockwise and remove the bulb from the headlamp.
WARNING
Refer to Halogen Bulb Warning .

Headlamp Aiming (Chevrolet/GMC)

Headlamp aiming is done with the low beam lamps. The high beam lamps will be correctly aimed if the low beam lamps are aimed properly.

Screen Method for Headlamp Aiming (Visual Aim)

The screen method requires an area set up specifically for headlamp aim.

The area should consist of a level surface large enough to allow for a vehicle and an additional 7.62 m (25 ft) as measured from the face of the headlamps to the aiming screen.

The screen should be a wall or other flat surface at least 1.52 m (5 ft) high by 3.66 m (12 ft) wide with a matte white surface well shaded from extraneous light, and 90 degrees to the floor. The screen should be provided with a permanent vertical reference line 0.61 m (2 ft) from the left edge of the screen, 2 laterally adjustable vertical tapes, and one vertically adjustable horizontal tape.

After the aiming screen has been set up and located, paint or tape a reference line on the floor 15.24 m (50 ft) from the vertical reference line on the screen. This line should be perpendicular to the aiming screen and a mark placed at 7.62 m (25 ft) from the screen.

Headlamp Aiming Procedure

  1. Align the left tires of the vehicle with the reference line extending from the screen with the headlamps aligned with the reference line.
  2. Remove any snow, ice or mud from the vehicle.
  3. The vehicle should be fully assembled and all other work stopped while the headlamp aiming is being done.
  4. The vehicle should contain cargo or be loaded to represent normal vehicle use.
  5. Tires should be properly inflated.
  6. Rock the vehicle to stabilize the suspension.
  7. Measure from the floor to the center of the lamp bulb on the vehicle. Some lamps have an aim dot marked on the lens.
  8. At the screen, measure from the floor and place the horizontal tape at the measured distance.
  9. Measure from the reference line on the floor to the left headlamp bulb centerline (1).
  10. At the screen, measure from the reference line and place the vertical tape at the measured distance (2).
  11. Measure from the reference line on the floor to the right headlamp bulb centerline.
  12. At the screen, measure from the reference line and place the vertical tape at the measured distance.
  13. Turn the headlamps ON.
  14. Block the light from projecting onto the screen from the passenger side headlamp. This will allow the cutoff in the beam pattern from the drivers side to be more pronounced for easier aim verification.
  15. On this vehicle you will be verifying the aim of the vertical cutoff on the right side of the lamp vertical bulb centerline as it is projected onto the aim board.
  16. If the location of the cutoff projected onto the board differs from (Scheme 4) then an adjustment to the beam pattern location is necessary.
  17. Adjust the vertical headlamp adjustment screw until the Right Gradient Line (Cutoff Line) is set at the Horizontal Axis within +/- 2.0 inches (2) measured at 7.62 m (25 ft).
  18. Verify proper aim location.
  19. Repeat the aiming procedure for the passengers side headlamp while blocking the light from projecting onto the screen from the drivers side headlamp.

Scheme 31

Scheme 31: Front Fog Lamp Replacement (Chevrolet)
Scheme 31: Front Fog Lamp Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedures Remove either the LF or RF wheelhouse liners. Refer to Front Wheelhouse Liner Replacement - Left Side (Chevrolet) or Front Wheelhouse Liner Replacement - Left Side (GMC) for the LF or Front Wheelhouse Liner Replacement - Right Side (Chevrolet) or Front Wheelhouse Liner Replacement - Right Side (GMC) for the RF wheelhouse liner. Disconnect the electrical connector. From inside the from bumper fascia, using a blunt instrument, pinch the retainers and push outward on the 2 upper mounting studs for the fog lamp. Using the same blunt instrument, pinch the retainer and push outward on the lower adjustment screw for the fog lamp. Aim the fog lamps after the fog lamp has been replaced. Refer to Fog Lamp Aiming .
1Fog Lamp Retainers (Qty: 3) Procedure Install the retainers back onto the fog lamp upper mounting studs. Install the retainer onto the fog lamp adjusting screw. Firmly push the lamp back into the lower bumper fascia until all three retainers are engaged to the fascia.
2Fog Lamp Assembly WARNING: Refer to Halogen Bulb Warning . Tip: Transfer the bulb assembly as needed.
WARNING
Refer to Halogen Bulb Warning .

Scheme 32

Scheme 32: Front Fog Lamp Replacement (GMC)
Scheme 32: Front Fog Lamp Replacement (GMC)
CalloutComponent Name
Preliminary Procedures Remove either the LF or RF wheelhouse liners. Refer to Front Wheelhouse Liner Replacement - Left Side (Chevrolet) or Front Wheelhouse Liner Replacement - Left Side (GMC) for the LF or Front Wheelhouse Liner Replacement - Right Side (Chevrolet) or Front Wheelhouse Liner Replacement - Right Side (GMC) for the RF wheelhouse liner. Disconnect the electrical connector. From inside the from bumper fascia, using a blunt instrument, pinch the retainers and push outward on the 2 upper mounting studs for the fog lamp. Using the same blunt instrument, pinch the retainer and push outward on the lower adjustment screw for the fog lamp. Aim the fog lamps after the fog lamp has been replaced. Refer to Fog Lamp Aiming .
1Fog Lamp Assembly WARNING: Refer to Halogen Bulb Warning . Tip: Transfer the bulb assembly as needed.
2Fog Lamp Retainers (Qty: 3) Procedure Install the retainers back onto the fog lamp upper mounting studs. Install the retainer onto the fog lamp adjusting screw. Firmly push the lamp back into the lower bumper fascia until all three retainers are engaged to the fascia.
WARNING
Refer to Halogen Bulb Warning .

Scheme 33

Scheme 33: Front Fog Lamp Bulb Replacement (Chevrolet)
Scheme 33: Front Fog Lamp Bulb Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedures Reach under the front air deflector in order to access the fog lamp bulb socket. Disconnect the electrical connector.
1Fog Lamp Bulb WARNING: Refer to Halogen Bulb Warning . Tip: Squeeze the tabs and rotate in order to release the bulb socket from the fog lamp assembly.
WARNING
Refer to Halogen Bulb Warning .

Scheme 34

Scheme 34: Front Fog Lamp Bulb Replacement (GMC)
Scheme 34: Front Fog Lamp Bulb Replacement (GMC)
CalloutComponent Name
Preliminary Procedures Reach under the front air deflector in order to access the bulb socket. Disconnect the electrical connector.
1Fog Lamp Bulb WARNING: Refer to Halogen Bulb Warning . Tip: Squeeze the tabs and rotate the bulb socket in order to release the bulb socket from the fog lamp assembly.
WARNING
Refer to Halogen Bulb Warning .

Fog Lamp Aiming

The front fog lamps must be aimed for proper illumination of the road. The front fog lamp aim should be checked when a new front fog lamp assembly is installed, or if service or repairs in the front end area may have disturbed the front fog lamp mounting.

Preparation Procedure

IMPORTANTHorizontal aim is not adjustable on this vehicle. Vertical aim is adjusted by an adjusting screw located on the bottom rear of the fog lamp. Prior to aiming the fog lamps, perform the following steps
  1. Completely assemble all of the components on the vehicle.
  2. Park the vehicle on a level surface.
  3. Stop all unnecessary operations or work on the vehicle that affect the vehicle trim.
  4. Close the doors and ensure that the vehicle has no load other than the driver.
  5. Stabilize the suspension by rocking the vehicle sideways.
  6. Ensure that the fuel level is 1/2 full.
  7. Ensure that the tires are inflated to the proper pressure.
  8. Ensure that the driver or a similar weight, approximately 75 kg (165 lb), is in the vehicle driver seat.

Aiming Procedure

  1. Park the vehicle on a level surface 7.6 m (25 ft) (3) away from a wall or other flat surface.
  2. Measure the distance from the floor to the center of the fog lamp (5).
  3. Using this measurement, mark the horizontal centerline of the fog lamp (1) on the flat surface directly in front of the vehicle.
  4. Remove the front portion of the front wheel liner in order to access the adjusting screw.
  5. Turn ON the fog lamps.
  6. Reach inside of the front portion of the fender liner in order to access the fog lamp vertical adjustment screw on the bottom of the fog lamp.
  7. Adjust the fog lamp so that the top edge of the fog lamp beam pattern is 100 mm (4 in) below the horizontal centerline (2).
  8. Turn OFF the fog lamps.
  9. Secure the forward edge of the front fender liner.

Scheme 35

Scheme 35: Front Side Marker Lamp Bulb Replacement (GMC)
Scheme 35: Front Side Marker Lamp Bulb Replacement (GMC)
CalloutComponent Name
Preliminary Procedure: Remove either the LF or RF headlamp assembly. Refer to Headlamp Replacement (Chevrolet) or Headlamp Replacement (GMC HD) or Headlamp Replacement (HD Diesel) .
1Lamp Harness Socket Tip: Rotate the marker lamp socket a quarter turn counterclockwise and remove the lamp socket from the headlamp assembly.
2Front Side Marker Lamp Bulb Tip: Pull the front side marker lamp bulb straight from the lamp socket.

Scheme 36

Scheme 36: Roof Marker Lamp Replacement (Without SRW)
Scheme 36: Roof Marker Lamp Replacement (Without SRW)
CalloutComponent Name
1Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 2 N.m (18 lb in)
2Roof Outer Lamp Assembly Tip: Lift the lamp cover lens and replace the bulb as needed.
CAUTION
Refer to Fastener Caution .

Scheme 37

Scheme 37: Roof Marker Lamp Replacement (U01)
Scheme 37: Roof Marker Lamp Replacement (U01)
CalloutComponent Name
1Screw (Qty: 3) CAUTION: Refer to Fastener Caution . Tighten: 2 N.m (18 lb in)
2Roof Outer Lamp Assembly Tip: Lift the lamp cover lens and replace the bulb as needed.
CAUTION
Refer to Fastener Caution .

Scheme 38

Scheme 38: Parking and Turn Signal Lamp Bulb Replacement (Chevrolet)
Scheme 38: Parking and Turn Signal Lamp Bulb Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedure: Remove either the LF or RF headlamp assembly in order to access the headlamp bulbs. Refer to Headlamp Replacement (Chevrolet) , Headlamp Replacement (GMC HD) or Headlamp Replacement (HD Diesel) .
1Directional Bulb Sockets (Qty: 2) WARNING: Refer to Halogen Bulb Warning . Tip: Rotate the bulb sockets a quarter turn counter-clockwise to access the bulbs.
2Directional Bulbs (Qty: 2) Tip: Pull the bulbs straight from the lamp sockets.
WARNING
Refer to Halogen Bulb Warning .

Scheme 39

Scheme 39: Parking and Turn Signal Lamp Bulb Replacement (GMC)
Scheme 39: Parking and Turn Signal Lamp Bulb Replacement (GMC)
CalloutComponent Name
Preliminary Procedure: Remove either the LF or RF headlamp assembly. Refer to Headlamp Replacement (Chevrolet) or Headlamp Replacement (GMC HD) or Headlamp Replacement (HD Diesel) .
1Directional Lamp Bulb Socket Tip: Rotate the marker lamp socket a quarter turn counterclockwise and remove the lamp socket from the headlamp assembly.
2Directional/DRL Bulb Tip: Pull the marker lamp bulbs straight from the lamp bulb socket.

Scheme 40

Scheme 40: Pickup Box Identification Lamp Replacement (Chevrolet HD)
Scheme 40: Pickup Box Identification Lamp Replacement (Chevrolet HD)
CalloutComponent Name
1Pick Up Box Identification Lamp Assembly Tip: Release the 3 integral clips securing the lamp assembly to the pick up box end panel.
2Pick Up Box Identification Lamp Electrical Connector

Scheme 41

Scheme 41: Pickup Box Identification Lamp Replacement (GMC HD)
Scheme 41: Pickup Box Identification Lamp Replacement (GMC HD)
CalloutComponent Name
1Pick Up Box Identification Lamp Assembly Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 2.5 N.m (22 lb in)
2Pick Up Box Identification Lamp Assembly
3Pick Up Box Identification Lamp Electrical Connector
4Rear Cross Sill Nut (Qty: 2)
CAUTION
Refer to Fastener Caution .

Scheme 42

Scheme 42: Rear Fender Clearance Lamp Replacement
Scheme 42: Rear Fender Clearance Lamp Replacement
CalloutComponent Name
Preliminary Procedure Reach inside the rear fender and wheelhouse in order to disconnect the electrical connector for the rear fender lamp from the main chassis harness. Disengage the retainer securing the connector to the pick up box panel brace. From inside the wheelhouse push inward on the locking tab for the lamp assembly and push the lamp outward from the fender. Remove the lamp and electrical harness.
1Rear Fender Clearance Lamps

Scheme 43

Scheme 43: High Mount Stop Lamp Replacement (Extended and Crew Cab)
Scheme 43: High Mount Stop Lamp Replacement (Extended and Crew Cab)
CalloutComponent Name
1High Mounted Stop and Cargo Lamp Opening Cover Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 2.5 N.m (22 lb in)
2High Mounted Stop and Cargo Lamp Opening Cover Tip: Pull the lamp rearward in order to access the electrical connector.
3Electrical Connector
4High Mounted Stop and Cargo Lamp Opening Cover Retainer Clip (Qty: 2)
CAUTION
Refer to Fastener Caution .

Scheme 44

Scheme 44: High Mount Stop Lamp Replacement (Regular Cab)
Scheme 44: High Mount Stop Lamp Replacement (Regular Cab)
CalloutComponent Name
1High Mounted Stop and Cargo Lamp Opening Cover Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 2.5 N.m (22 lb in)
2High Mounted Stop and Cargo Lamp Opening Cover Tip: Pull the lamp rearward in order to access the electrical connector.
CAUTION
Refer to Fastener Caution .

Scheme 45

Scheme 45: High Mount Stop Lamp Bulb Replacement (GMC Denali)
Scheme 45: High Mount Stop Lamp Bulb Replacement (GMC Denali)
CalloutComponent Name
Preliminary Procedure: Remove the high mounted stop lamp cover assembly. Refer to High Mount Stop Lamp Replacement (Extended and Crew Cab) or High Mount Stop Lamp Replacement (Regular Cab) .
1High Mounted Stop and Cargo Lamp Opening Cover Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 2.5 N.m (22 lb in)
2High Mounted Stop and Cargo Lamp Opening Cover
3Cargo Lamp Bulb (Qty: 2) Tip: Rotate the bulb sockets a quarter turn counter-clockwise to unlock in order to remove the bulbs from the bulb sockets.
4Brake Lamp Bulb (Qty: 2) Tip: Rotate the bulb sockets a quarter turn counter-clockwise to unlock in order to remove the bulbs from the bulb sockets.
CAUTION
Refer to Fastener Caution .

Scheme 46

Scheme 46: Backup Lamp Bulb Replacement (Chevrolet)
Scheme 46: Backup Lamp Bulb Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedure: Remove either the LR or RR tail lamp assembly. Refer to Tail Lamp Replacement (Chevrolet) or Tail Lamp Replacement (GMC) .
1Back Up Lamp Bulb

Scheme 47

Scheme 47: Backup Lamp Bulb Replacement (GMC)
Scheme 47: Backup Lamp Bulb Replacement (GMC)
CalloutComponent Name
Preliminary Procedure: Remove either the LR or RR tail lamp assembly. Refer to Tail Lamp Replacement (Chevrolet) or Tail Lamp Replacement (GMC) .
1Back Up Lamp Bulb
  1. Ensure the headlamp switch is in the OFF position.
  2. Reach under the rear bumper and press on the lens end of the cover in order to release the locking tab.
  3. Remove the lens housing from the bumper assembly.
  4. Remove the bulb.
  1. Install the bulb.
  2. Install the rear edge of the lens housing into the rear bumper.
  3. Push on the lens side of the housing in order to snap the housing into the rear bumper assembly.
  4. Inspect the operation.

Scheme 48

Scheme 48: Rear License Plate Lamp Replacement (VF7)
Scheme 48: Rear License Plate Lamp Replacement (VF7)
CalloutComponent Name
1License Plate Lamp Electrical Connector Tip: Disconnect the electrical connector from the rear junction block.
2Rear License Plate Lamp Assembly

Scheme 49

Scheme 49: Rear License Plate Lamp Bulb Replacement
Scheme 49: Rear License Plate Lamp Bulb Replacement
CalloutComponent Name
Procedure Reach under the rear bumper for the bulb socket. Turn the bulb socket counter-clockwise and pull the bulb socket out of the connector. Pull the old bulb from the socket, keeping the bulb straight as you pull it out. Install the new bulb.
1Bulb Socket
2Rear License Plate Lamp Bulb

Scheme 50

Scheme 50: Tail Lamp Replacement (Chevrolet)
Scheme 50: Tail Lamp Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedure: Open the endgate in order to access the tail lamp assembly screws.
1Tail Lamp Assembly Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 2 N.m (18 lb in)
2Tail Lamp Wiring Harness Assembly Connector
3Tail Lamp Assembly Tip: Upon installation, push inward on the tail lamp in order to seat the 2 locating pins in the body panel.
CAUTION
Refer to Fastener Caution .

Scheme 51

Scheme 51: Tail Lamp Replacement (GMC)
Scheme 51: Tail Lamp Replacement (GMC)
CalloutComponent Name
Preliminary Procedures Open the endgate in order to access the tail lamp assembly screws. Disconnect the electrical harness to the tail lamp.
1Tail Lamp Assembly Screws (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 2 N.m (18 lb in)
2Tail Lamp Assembly Tip: Upon installation, push inward on the outer edge of the tail lamp in order to seat the 2 locating pins in the body panel.
CAUTION
Refer to Fastener Caution .

Scheme 52

Scheme 52: Tail Lamp Bulb Replacement (Chevrolet)
Scheme 52: Tail Lamp Bulb Replacement (Chevrolet)
CalloutComponent Name
Preliminary Procedure: Remove the rear tail lamp. Refer to Tail Lamp Replacement (Chevrolet) or Tail Lamp Replacement (GMC) .
1Park and Turn Signal Lamp Bulb (Qty: 2)

Scheme 53

Scheme 53: Tail Lamp Bulb Replacement (GMC)
Scheme 53: Tail Lamp Bulb Replacement (GMC)
CalloutComponent Name
Preliminary Procedure: Remove the rear tail lamp. Refer to Tail Lamp Replacement (Chevrolet) or Tail Lamp Replacement (GMC) .
1Park and Turn Signal Lamp Bulbs (Qty: 2)

Exterior Lamps

The exterior lighting system consists of the following lamps

  1. The headlamps
  2. The daytime running lamps (DRL)
  3. The front fog lamps
  4. The park, tail and marker lamps
  5. The exterior courtesy lamps
  6. The turn signal/hazard lamps
  7. The stop lamps
  8. The backup lamps
  9. The cargo lamps
  10. The roof beacon lamp (if equipped)

Headlamps

The headlamps may be turned on in 2 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC the headlamps will be in DRL operation in daylight conditions, or headlamp operation in low light conditions.

Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the headlamp switch on input circuit when the headlamp switch is in the HEAD position. When the headlamp switch is in the AUTO position, the BCM determines headlamps ON/OFF by the voltage from the ambient light sensor.

If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.

The high beam indicator is illuminated when the instrument cluster receives a GMLAN serial data message from the BCM that the high beams are illuminated.

High Beams

The high beam headlamps receive voltage from the headlamp high relay located in the underhood fuse block. The BCM controls the relay on the headlamp high beam relay control circuit. High beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is grounded, the BCM grounds the headlamp high beam relay control circuit, illuminating the high beam headlamps. The right and left high beam circuits are independent and are fused independently in the underhood fuse block.

Low Beams

The low beam headlamps receive voltage from the headlamp low beam relay located in the underhood fuse block. The BCM controls the relay on the headlamp low beam relay control circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is open, the BCM grounds the headlamp low beam relay control circuit, illuminating the low beam headlamps. The right and left low beam circuits are independent are fused independently in the underhood fuse block.

Daytime Running Lamps (DRL)

The DRL will only operate while the engine is running and the headlamp switch is in the AUTO position. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate. The ambient light sensor is a light sensitive transistor that varies its voltage signal to the BCM in response to changes to the outside ambient light level. When the BCM receives this signal it will either turn on the dedicated DRL on the X88, the low beam headlamps only as DRL on the Z88, or the headlamps, park, and tail lamps for auto headlamp operation in low light conditions. Any function or condition that turns on the headlights will cancel the daytime running lamps operation. The DRL can be manually turned OFF by activating the AHL/DRL switch in the headlamp switch. The AHL/DRL defeat switch sends a ground signal through the DRL switch signal circuit to the BCM. The BCM then turns OFF the DRL. When the AHL/DRL are manually turned OFF at the headlamp switch, the AHL/DRL will default to ON with the next ignition cycle. With the headlight switch in the AUTO position, the DRL will either be turned ON or OFF after an approximate 8 second delay, depending on whether daylight or low light conditions are sensed. When the BCM energizes the DRL relay, the DRL receives voltage on the DRL supply voltage circuit.

Fog Lamps

With both the ignition switch in the RUN position, and the park lamps ON, the fog lights will illuminate when the driver depresses the fog lamp switch. The BCM receives the park lamp ON signal from the interior park lamps supply voltage signal circuit. With the headlamp switch in either the park or headlamp position, and the fog lamp switch is in the ON position, the BCM will ground the fog lamp relay control circuit causing the relay to energize. The current flows from the fog lamp relay to both front fog lamps. The state of the fog lamps will remain the same until the fog lamp switch position is changed, or the ignition switch is cycled OFF and ON. Fog lamp operation will be cancelled whenever the park lamps, are turned OFF or the high beam headlights have been selected.

Park, Tail and Marker Lamps

The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in the PARK or HEAD position or anytime the headlights are requested. The underhood fuse block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The BCM provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned ON, the BCM energizes the park lamp relay. If the headlight switch is left in the ON position, the inadvertent power control feature will turn OFF the park, tail and marker lamps approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the park, tail and marker lamps will remain on until turned OFF or the battery runs dead.

Exterior Courtesy Lamps

The BCM, driver door switch, and the passenger door switch communicate through the GMLAN serial data system. The driver door switch and passenger door switch supply power and ground to the left and right exterior lamps respectively. When the BCM commands illuminated entry, a command is also sent to the door switches for illumination of the exterior courtesy lamps. If the door locks are activated to the LOCK position, or if the ignition switch is turned to either the ON or RUN position the exterior courtesy lamps will deactivate immediately.

Turn Signal/Hazard Lamps

When the turn signal switch is placed in either the left or right position, a ground signal is completed from the turn signal switch to the BCM. When the hazard flasher switch is activated, a ground signal is completed from the turn signal/hazard switch to the BCM. The BCM then sends an ON-OFF voltage signal through the fuses to the appropriate turn signal and side repeater (export only) lamps or to all of the turn signal fuses for hazard operation. The driver door switch and passenger door switch also receive voltage from the BCM turn signal supply voltage circuits for the mirror turn signals. The door switches have no function or control of the mirror turn signals other than a pass through connection for the circuits. The audio chime is also activated when the turn signals are ON. The instrument panel cluster (IPC) receives the signals to activate the turn signal indicators over the GMLAN serial data system. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators.

Stop Lamps

When the driver presses the brake pedal, the switch contacts open and battery positive voltage is interrupted to the BCM. The BCM then supplies voltage to both the turn/stop lamp supply voltage circuit and trailer rear turn/stop lamp supply voltage circuits. The BCM also supplies a control voltage to the CHMSL relay energizing the relay and illuminating the CHMSL.

Backup Lamps

The backup lamp request signal is sent from the PCM to the BCM on the GMLAN serial data system. This signal is based on the park neutral position (PNP) switch signal. The BCM supplies voltage to the backup relay and to the automatic day/night mirror when the vehicle is in reverse. The backup relay supplies a voltage on the backup lamp supply voltage circuit to the backup lamps and trailer backup circuit.

Cargo Lamps

The cargo lamp is controlled by the courtesy lamp supply voltage circuit. When the dimmer switch is turned clockwise to the farthest setting, the BCM recieves an input from the dimmer switch for courtesy lamps and cargo lamp to be commanded ON.

Clearance Lamps

The clearance lamps, are turned ON when the headlamp switch is placed in the PARK or HEAD position or anytime the headlamps are requested. The underhood fuse block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The BCM provides a ground or control circuit to the park lamps relay coil circuit. When the park lamps are turned ON, the BCM energizes the park lamp relay. If the headlamp switch is left in the ON position, the inadvertent power control feature will turn OFF the park, tail and clearance lamps approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlamp switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the park, tail and marker lamps will remain ON until turned OFF or the battery runs dead.

Interior Lamps

The interior lighting consists of 2 groups. The first group includes lamps that may not be dimmed.

  1. Courtesy/illuminated entry lamps
  2. Dome lamps
  3. Map lamps
  4. Reading lamps
  5. Vanity mirror lamps

Courtesy/Illuminated Entry Lamps

The courtesy/illuminated entry lamps, may be manually turned ON or OFF by placing the interior lamp switch in the ON or OFF position. If an outside door handle is lifted and a door is opened, the courtesy/illuminated entry lamps illuminate. After all the doors have been closed the courtesy/illuminated entry lamps will remain illuminated approximately 15 seconds. The body control module (BCM) will then turn them OFF through the theater dimming feature. The courtesy/illuminated entry lamps will also turn ON prior to any door being opened, and remain illuminated approximately 40 seconds when the driver removes the ignition key. When the driver places the dome lamp defeat switch in the OFF position, the courtesy/illuminated entry lamps will be disabled.

The BCM and the door modules communicate through the GMLAN serial data circuit for the lamp illumination commands of the door switch signals. The left and right rear door latch switches are both on one circuit that is also an input to the BCM.

The left and right front door courtesy lamps (if equipped) receive voltage and ground from the driver door switch and the passenger door switch respectively. The remaining courtesy lamps are controlled and receive voltage from the BCM. Voltage for the courtesy lamp supply voltage circuit is from the INT LTS fuse in the instrument panel fuse block.

Keyless Entry Interior Illumination

When the driver uses the door key in order to unlock the doors, the body control module (BCM) receives a door unlock signal. The BCM must have inputs or serial data messages that indicate that the ignition switch is OFF, the courtesy lamp switch is OFF and all the doors are closed. The BCM will then activate the interior lamps. The courtesy lamps will remain ON, approximately 15 seconds after the door is closed. The BCM will then turn them OFF through the theater dimming feature. If the door locks are activated to the LOCK position, or if the ignition switch is turned to either the RUN or CRANK position the courtesy lamps will turn OFF immediately.

When the driver uses the remote function actuator transmitter to unlock the doors, trunk or presses the panic button, the BCM will keep the courtesy lamps ON approximately 40 seconds. When the driver uses the remote function actuator transmitter to lock the doors, the BCM will keep the courtesy lamps on approximately 2 seconds. If the ignition switch is turned to either the RUN or CRANK position the courtesy lamps will turn OFF immediately.

Vanity Lamps

The inadvertent power supply voltage circuit of the body control module (BCM) provides battery positive voltage to each vanity mirror lamp. When the vanity mirror cover on the sunshade is opened, a switch closes to provide a ground circuit and the vanity lamp illuminates.

Reading Lamps

The inadvertent power supply voltage circuit of the body control module (BCM) provides battery positive voltage to the reading lamps. The reading lamps and switch are integral to the courtesy/reading lamp assembly. When the switch is closed, voltage is supplied and the lamp illuminates.

Battery Rundown Protection/Inadvertent Power

The body control module (BCM) inadvertent power supply voltage circuit provides battery positive voltage to all of the interior reading lamps, visor vanity mirror lamps, and cargo lamps if equipped. In the event that any of these lamps were to remain illuminated for a period of more than 10 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power supply voltage circuit to prevent a total battery discharge condition.

Interior Lamps Dimming

The second interior lighting group includes lamps which may be dimmed. This group may use a combination of vacuum fluorescent (VF) illumination, LED illumination and incandescent lamps.

When the ignition switch is turned to the RUN position, the radio VF display turns ON at maximum brightness. When the park lamps are ON, all incandescent and LED back lighting turn ON at the dimming level indicated by the instrument panel (I/P) dimmer switch. At the same time all VF displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the body control module (BCM). When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all incandescent back lighting lamps are provided with a specific voltage. When the I/P dimmer switch is moved from MIN to MAX, all VF displays, as well as all incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch.

The following switches and components have back lighting when the park lamps are ON

  1. The instrument panel cluster (IPC)
  2. Window and heated seat switches
  3. Rear HVAC switches
  4. Sunroof switch
  5. Accessory switches
  6. Fog lamp switches
  7. Garage door opener
  8. Rear parking assist (RPA) disable switches
  9. Transfer case shift control switch
  10. Power take off switch
  11. Roof beacon switch
  12. Sliding rear window switch
  13. PRNDL lamps
  14. Traction control switch
  15. Steering wheel control switches
  16. Integrated trailer brake controller switch

The left and right front door switch illumination is controlled, receives voltage and ground from the driver door switch and passenger switch respectively. The radio is also a GMLAN module and has full control of its illumination. The BCM, door switches, and radio communicate through GMLAN serial data for the lamp illumination commands.

The various switches, HVAC control assembly, and the PRNDL lamps receive voltage and are controlled by the BCM on the I/P lamps dimming control circuit.

The following indicators receive voltage from the BCM and are controlled by ground from a switch or from various modules

  1. Tow indicator
  2. Transfer case control switch 4WD position indicators
  3. Fog lamp indicators
  4. Radio
  5. Analog clock
  6. HVAC control assembly
  7. Instrument panel cluster (IPC)
  8. Driver information center (DIC)
  9. Headlamp and panel dimmer switch
  10. Rear parking assist (RPA) indicator

The indicators receive voltage from the BCM on the LED dimming circuit. Control for the indicators is from the various modules or switches. Voltage for the LED dimming supply circuit, instrument panel lamps dimming control circuit and the instrument panel lamps dimming supply circuit is from the BCM.

The modules controlling the above indicators are as follows

  1. Transfer case shift control module
  2. BCM

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Component Connector End Views
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Diagnostic Repair Verification
• Relay Replacement (Attached to Wire Harness)
• Brake Warning Indicator Malfunction
• Checking Aftermarket Accessories
• Backup Lamp Switch Replacement
• Front Side Door Lock Replacement
• Turn Signal Multifunction Switch Replacement
• Front Seat Heater Switch Replacement
• Steering Wheel Control Switch Assembly Replacement
• Driver Information Display Switch Replacement (with RPO SLT)
• Knee Bolster Replacement (With RPO SLT)
• Fastener Caution
• Radiator Grille Replacement (Chevrolet)
• Front Bumper Impact Bar Replacement (Chevrolet)
• Halogen Bulb Warning
• Front Wheelhouse Liner Replacement - Left Side (Chevrolet)
• DTC B1395
• Daytime Running Lamps Malfunction
• Hazard Lamps Malfunction
• Backup Lamps Malfunction
• Backup Lamp Switch Malfunction
• Courtesy Lamp Malfunction
• Door Open Switch Malfunction - Front w/AN3
• Door Open Switch Malfunction - Rear
• Dome/Interior Lamp Switch Malfunction
• Exterior Lamps Circuit Test
• Reading Lamps Malfunction
• Vanity Mirrors Malfunction
• Ambient Light Sensor Malfunction
• Fog Lamp Switch Malfunction
• Fog Lamp Switch Replacement (with RPO SLT)
• Fog Lamp Switch Replacement (without RPO SLT)
• Headlamp Switch Malfunction
• Headlamp Dimmer Switch Malfunction
• Headlamps Malfunction - Low Beam
• Headlamps Malfunction - High Beam
• Headlamp Replacement (GMC HD)
• Headlamp Replacement (HD Diesel)
• Interior Backlighting Malfunction - Incandescent
• LED Dimming Circuit Test
• Dimmer Switch Circuit Test
• Interior Backlighting Malfunction - LED
• Park Lamp Switch Circuit Test
• Park Lamp Relay Circuit Test
• Stop Lamp Switch Circuit Test
• CHMSL Relay Control Circuit Test
• Turn Signal Switch Malfunction
• Fastener Tightening Specifications
• Fog Lamp Aiming