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Contents Wiring diagrams Section: Exterior Lights All sections

Lighting System Chevrolet Express H1500

Exterior Lights 25 illustrations ~23762 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Backup Lens to Lamp Assembly Screws1.5 N.m13 lb in
Fog Lamp Lens to Fog Lamp Assembly Screws1.5 N.m13 lb in
Headlamp to Radiator Support Bolts10 N.m89 lb in
High Mounted Stop Lamp to Upper Lamp Applique Screws1.5 N.m13 lb in
License Plate Lamp to License Plate Pocket Screws1.5 N.m13 lb in
Park/Turn Signal Lamp to Radiator Grille Screws1.5 N.m13 lb in
Retaining Ring to Headlamp Housing Screws1.5 N.m13 lb in
Side Marker Lamp to Body Screws1.5 N.m13 lb in
Tail Lamp to Quarter Panel Nuts5 N.m44 lb in

Fastener Tightening Specifications

Scheme 1

Scheme 1: Headlamp and Daytime Running Lamp Controls Wiring Schematics
Scheme 1: Headlamp and Daytime Running Lamp Controls Wiring Schematics

Scheme 2

Scheme 2: Low Beam and Daytime Running Lights (DRL) Wiring Schematics
Scheme 2: Low Beam and Daytime Running Lights (DRL) Wiring Schematics

Scheme 3

Scheme 3: High Beams Wiring Schematics
Scheme 3: High Beams Wiring Schematics

Scheme 4

Scheme 4: Park Lamp Controls and Park Lamps Wiring Schematics
Scheme 4: Park Lamp Controls and Park Lamps Wiring Schematics

Scheme 5

Scheme 5: Turn Signal Controls and Front Turn Signal Lamps Wiring Schematics
Scheme 5: Turn Signal Controls and Front Turn Signal Lamps Wiring Schematics

Scheme 6

Scheme 6: Rear Turn Signal Lamps Wiring Schematics
Scheme 6: Rear Turn Signal Lamps Wiring Schematics

Scheme 7

Scheme 7: Stop Lamp Controls and CHMSL Wiring Schematics
Scheme 7: Stop Lamp Controls and CHMSL Wiring Schematics

Scheme 8

Scheme 8: Backup Lamps and Backup Alarm Wiring Schematics
Scheme 8: Backup Lamps and Backup Alarm Wiring Schematics

Scheme 9

Scheme 9: Inadvertent Lamp Control Wiring Schematics
Scheme 9: Inadvertent Lamp Control Wiring Schematics

Scheme 10

Scheme 10: Dome Fluorescent Work Lamps (PRP with UF2) Wiring Schematics
Scheme 10: Dome Fluorescent Work Lamps (PRP with UF2) Wiring Schematics

Scheme 11

Scheme 11: Dimming Controls and LED Dimming Wiring Schematics
Scheme 11: Dimming Controls and LED Dimming Wiring Schematics

Scheme 12

Scheme 12: I/P Bulb Dimming (1 of 2) Wiring Schematics
Scheme 12: I/P Bulb Dimming (1 of 2) Wiring Schematics

Scheme 13

Scheme 13: I/P Bulb Dimming (2 of 2) Wiring Schematics
Scheme 13: I/P Bulb Dimming (2 of 2) Wiring Schematics

Diagnostic Code Index

DTCDescription
DTC B1395DTC B1395 03 Device Voltage Reference Output 1 Circuit Below Threshold DTC B1395 07 Device Voltage Reference Output 1 Circuit Above Threshold
DTC B1480DTC B1480 00 Battery Rundown Protection Circuit
DTC B2545DTC B2545 00 Backup Lamps Circuit
DTC B2555DTC B2555 00 Passenger Compartment Lamp Control Circuit
DTC B2575DTC B2575 00 Headlamp Control Circuit
DTC B257ADTC B257A 00 Headlamp Switch Input Signal Mismatch
DTC B2580DTC B2580 00 Headlamp High Beam Control Circuit
DTC B2585DTC B2585 00 Left Park Lamp Control Circuit
DTC B2600DTC B2600 00 Daytime Running Lamp Control Circuit
DTC B2610DTC B2610 00 Passenger Compartment Dimming 1 Circuit
DTC B2615 (with out YF7)DTC B2615 00 Passenger Compartment Dimming 2 Circuit
DTC B2615 (with YF7)DTC B2615 00 Passenger Compartment Dimming 2 Circuit
DTC B2625DTC B2625 00 Display Dimming Pulse Width Modulation (PWM) Output Circuit
DTC B2645DTC B2645 03 Ambient Light Sensor Circuit Below Threshold DTC B2645 07 Ambient Light Sensor Circuit Above Threshold
DTC B2652DTC B2652 00 Passenger Compartment Dimming 3
DTC B3445DTC B3445 00 Center High Mounted Stop Lamp (CHMSL) Circuit
DTC B3600DTC B3600 03 Passenger Compartment Dimming Request Signal Circuit Voltage Below Threshold
DTC B3884DTC B3884 00 Stoplamp Circuit
DTC C0277 or C0890DTC C0277 06 Brake Pedal Position Sensor Circuit Short to Ground or Open DTC C0277 07 Brake Pedal Position Sensor Circuit Voltage Above Threshold DTC C0277 09 Brake Pedal Position Sensor Circuit Rate of Change Above Threshold DTC C0277 4B Brake Pedal Position Sensor Calibration Not Learned DTC C0890 03 Device Voltage Reference Output 3 Circuit Voltage Below Threshold DTC C0890 07 Device Voltage Reference Output 3 Circuit Voltage Above Threshold
DTC C0297DTC C0297 00 Brake Applied Output Circuit

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BCM Supply VoltageB1395 03, B3600 03B1395 03, B3600 03
I/P Dimming Voltage ReferenceB1395 03, B3600 03B3600 03B1395 07
Stop Lamp Switch SignalB1395 03, B3600 0322
Instrument Panel Lamps Dimmer Switch SignalB3600 03B3600 031
1. Interior Backlighting Malfunction 2. Stop Lamps Malfunction

Circuit/System Description

The body control module (BCM) supplies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the I/P lamps supply voltage circuit and the LED dimming supply circuit to all related interior lamps, illuminating them to the desired level of brightness.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

B1395 03

The BCM detects a voltage that is lower than 9 volts on the I/P dimming voltage reference circuit.

B1395 07

The BCM detects a voltage that is greater than 14 volts on I/P dimming voltage reference circuit.

Action Taken When the DTC Sets

The I/P lamps are not illuminated.

Conditions for Clearing the DTC

  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.

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__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 X3 harness connector at the BCM
  2. Ignition ON, 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.
  3. Ignition OFF, connect the X3 harness connector at the BCM and disconnect the harness connector at the headlamp switch.
  4. Ignition ON, verify that a test lamp illuminates between the B+ reference circuit terminal 15 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the BCM.
  5. Ignition OFF, disconnect the harness connector at the stop lamp switch.
  6. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  7. Install a 3A fused jumper wire between the signal circuit terminal D and the B+ circuit terminal C. Verify that the scan tool Stop Lamp Switch Status parameter is 1023 counts. If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, replace the headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BCM Supply VoltageB1480 00B1480 00
12-Volt ReferenceB1480 001
Inadvertent Lamps Ground1
1. Inadvertent Lamps Malfunction

Battery voltage is applied at all times to the body control module (BCM) from the BCM 2 fuse located in the underhood fuse block. The BCM then applies this voltage to the following lamps

  1. Underhood lamp
  2. Front reading lamps
  3. Middle reading lamps
  4. Rear reading lamp
  5. Vanity mirror lamps

In the event that any of these lamps were to remain illuminated for more the 20 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power courtesy lamps circuit to prevent total battery discharge.

Battery voltage must be between 9-16 volts.

The BCM detects a short ground on the inadvertent power courtesy lamp circuit.

The BCM will deactivate the inadvertent voltage to the courtesy lamps.

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

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the X3 harness connector at the BCM.
  2. Ignition ON, 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. If the circuit tests normal, and the B+ circuit fuse is open, test the control circuit and components listed below for a short to ground. If all circuits and components test normal, replace the BCM. BCM Harness Connector X2 Terminal 1 Underhood Lamp Front Courtesy/Reading Lamp Middle Courtesy/Reading Lamp Rear Courtesy/Reading Lamp Left Sunshade Lamp Right Sunshade Lamp
  3. If all circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Sunshade Illuminated Mirror Lamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Dome Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Dome Lamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Underhood Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  5. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Backup Lamps Relay B+11
Backup Lamps Relay ControlB2545 0011
Backup Lamps Control111
Backup Lamps Ground1
Backup Lamps Relay Ground1
1. Backup Lamps Malfunction

When the transmission range selector is placed in the REVERSE position, a signal is sent to the body control module (BCM). The BCM then applies voltage through the backup lamps relay control circuit energizing the backup lamps PCB relay. With the relay energized, battery voltage is applied through the left and right backup lamp fuses and the supply voltage circuits to the backup lamps. The engine may need to be running for the backup lamps to function.

Ignition ON. The backup lamps must be commanded ON.

The BCM detects a short to ground on the backup lamps relay control circuit.

The BCM will deactivate the backup lamps for the remainder of the ignition cycle.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, place the transmission range selector in the REVERSE position. The backup lamps should illuminate.

  1. Ignition OFF, disconnect the X1 harness connector at the body fuse block.
  2. Connect a test lamp between the control circuit terminal K8 and ground.
  3. 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. 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. If all circuits test normal, replace the body fuse block.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Body Wiring Harness Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Courtesy Lamp Control CircuitB2555 0021
Inadvertent Power Courtesy Lamps32
Overhead Ground2
1. Overhead Console Lamp Always On 2. Overhead Console Lamp Malfunction 3. Inadvertent Power Courtesy Lamps Malfunction

The CTSY/RF TRN fuse supplies battery voltage to the body control module (BCM). When the BCM commands the courtesy lamps ON, it applies battery voltage through the courtesy lamp relay control circuit to the coil side of the OVRHD LAMPS Relay, energizing the relay. Battery voltage from the inadvertent power courtesy lamp circuit is applied through the switch side of the relay and the courtesy lamp supply voltage circuit to the overhead console lamp, illuminating the courtesy lamp. The BCM also applies battery voltage through the courtesy lamp supply voltage circuit to the left and right roof rail courtesy lamps and the front, middle, and rear door courtesy lamps. When any door is opened, the door open switch contacts close and the BCM receives a door-open input and it will illuminate the courtesy lamps. If the BCM receives a door lock or unlock input or a rear hatch open input, it will illuminate the courtesy lamps.

Battery voltage must be between 9-16 V.

The BCM detects a short to voltage in the courtesy lamp relay control circuit.

The BCM will deactivate the overhead lamps relay for the remainder of the ignition cycle.

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

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, remove the OVRHD LAMPS Relay from the rear fuse block.
  2. Connect a test lamp between the control circuit terminal 4 and ground.
  3. Ignition ON, command the 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 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. If the circuit tests normal, test or replace the overhead lamp relay.

Component Testing

Relay Test

  1. Ignition OFF, disconnect the relay.
  2. Test for 70-100 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals: 30 and 85 30 and 86 30 and 87 85 and 87 If not the specified value, replace the relay.
  4. Install a 10 A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87. If greater than the specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Relay Replacement (Within an Electrical Center)»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions) , «Relay Replacement (Attached to Wire Harness)»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Headlamp Low Beam Relay Control11B2575 00
1. Headlamps Malfunction - Low Beam

The low beam headlamps are controlled by two different inputs to the body control module (BCM), the headlamp switch, or when in the Auto mode, the ambient light sensor. When the BCM receives a low beam headlamps ON command, it grounds the headlamp low beam relay control circuit in order to energize the low beam PCB relay. With the relay energized, battery voltage is applied through switch side of the relay, both LO BEAM fuses, and the low beam supply voltage circuits to the low beam headlamps.

  1. The low beam headlamps are commanded ON.
  2. The headlamp dimmer switch must be in the low beam position.

The BCM detects a short to voltage on the headlamp low beam relay control circuit.

The BCM will deactivate the headlamp low beam PCB relay for the remainder of the ignition cycle.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, turn the headlamps ON. The headlamps should illuminate.

  1. Ignition OFF, disconnect the X5 harness connector at the BCM.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 23 and B+. If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.
  3. Install a 10 A fused jumper wire between the control circuit terminal 23 and ground. The low beam headlamps should illuminate. If the low beam headlamps do not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  4. If all circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Headlamp Switch Off SignalB257A 0022*
Park Lamp Switch On SignalB257A 00B257A 00B257A 00*
Headlamp Switch On SignalB257A 0022*
Headlamp Ground1
* Internal damage to the headlamp switch may occur if shorted to B+ 1. Headlamps Malfunction - Low Beam 2. Headlamp Switch Malfunction

The body control module (BCM) supplies a B+ reference voltage through each of the headlamp switch signal circuits to the headlamp switch. When the headlamp switch is in the AUTO position, all headlamp switch signal circuits to the BCM are open and the BCM operates in the automatic mode. When the headlamp switch is turned to the PARK position, only the park lamp switch signal circuit is pulled low signaling the park lamps ON request. When the headlamp switch is turned to the HEAD position, the park lamp and headlamp switch signal circuits are both pulled low, signaling the headlamps ON request. When the headlamp switch is turned to the OFF position, only the headlamp off switch signal circuit is pulled low, signaling the lights OFF request.

Ignition ON.

The BCM receives a mismatch signal between the headlamps OFF signal circuit, the headlamps ON signal circuit and the park lamps ON signal circuit.

The BCM disregards the headlamp switch input and defaults to automatic headlamp function.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON with the headlamp switch in the Auto position, observe the scan tool Exterior Lighting parameters listed below. All parameters should be Inactive.

  1. Auto Hdlp. Disable Sw.
  2. Headlamp Switch
  3. Parklamp Switch
  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition ON, test for B+ between the signal circuit terminals listed below and ground. Headlamp switch ON signal terminal 1 Park lamp switch ON signal terminal 2 Headlamp switch OFF signal terminal 3 If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  3. Install a 3A fused jumper wire between the park lamp ON signal circuit terminal 2 and ground. Verify the scan tool Parklamp 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.
  4. If all circuits test normal, replace the headlamp switch.

Component Test

IMPORTANTIf the switch tests open in any switch position other than Auto, test the switch signal circuits for a short to voltage before replacing the switch.

Headlamp Switch

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Test for infinite resistance between the signal terminal 3 and the ground terminal 8 with the switch in the Auto position. If not the specified value, replace the headlamp switch.
  3. Test for infinite resistance between the signal terminal 1 and the ground terminal 8 with the switch in the Auto position. If not the specified value, replace the headlamp switch.
  4. Test for less than 2.0 ohms between the signal terminal 3 and the ground terminal 8 with the switch in the Off position. If not the specified value, replace the headlamp switch.
  5. Test for less than 2.0 ohms between the signal terminal 1 and the ground terminal 8 with the switch in the Headlamp position. If not the specified value, replace the headlamp switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
High Beam Relay Control11B2580 00
1. Headlamps Malfunction - High Beams

The high beam headlamps can be controlled by two different inputs to the body control module (BCM), the dimmer switch and the flash to pass switch. When the BCM receives a high beam headlamps ON command, it grounds the headlamp high beam relay control circuit in order to energize the high beam PCB relay. With the relay energized, battery voltage is applied through switch side of the relay, both HI BEAM fuses, and the high beam supply voltage circuits to the high beam headlamps.

The high beam headlamps must be ON.

The BCM detects a short to voltage on the headlamp high beam relay control circuit.

The BCM will deactivate the headlamp high beam PCB relay for the remainder of the ignition cycle.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the High Beams ON with a scan tool. The High Beam Relay Command parameter should display On and the high beam headlamps should illuminate.

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 16 and B+. If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.
  3. Install a 10 A fused jumper wire between the control circuit terminal 16 and ground. The high beam headlamps should illuminate. If the high beam headlamps do not illuminate, test the control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  4. If all circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Park Lamp Relay Control11B2585 00
1. Park Lamps Malfunction

Battery positive voltage is applied at all times to both the coil and switched sides of the PRK LAMP relay. The park lamps are controlled by the body control module (BCM) by inputs from park lamp switch. When the BCM receives a park lamps ON command, it grounds the park lamps relay control circuit in order to energize the PRK LAMP relay. With the relay energized, battery voltage is applied through switch side of the relay, both PARK fuses, and the park lamp supply voltage circuits to all park, tail, and marker lamps.

Park lamps ON.

The BCM detects a short to voltage on the park lamp relay control circuit.

The BCM will deactivate the PRK LAMP relay for the remainder of the ignition cycle.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, turn the park lamps on. The park lamps should illuminate.

  1. Ignition OFF, disconnect the park lamp relay.
  2. Connect a test lamp between the control circuit terminal 86 and B+.
  3. Ignition ON, 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.
  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 (Within an Electrical Center)»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions) , «Relay Replacement (Attached to Wire Harness)»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
DRL Ambient Light Sensor SignalB2645 03B2645 07B2645 07
DRL Relay Control11B2600 00
Left Low Beam Headlamp Control222
Right Low Beam Headlamp Control222
DRL Ambient Light Sensor Low ReferenceB2645 07
Right Headlamp Low Beam Ground2
Right Headlamp Low Beam Ground2
1. Daytime Running Lamps (DRL) Malfunction 2. Headlamps Malfunction - Low Beam

Circuit Description

Battery positive voltage is applied at all times to both the coil and switched sides of the DRL PCB Relay. The daytime running lamps (DRL) are controlled by the body control module (BCM). The BCM grounds the DRL relay control circuit in order to energize the DRL PCB relay coil. With the relay energized, voltage is applied through the switch side of the relay, both LOW BEAM Fuses, and the headlamp low beam supply voltage circuits to the low beam headlamps.

Conditions for Running the DTCs

  1. The headlamp switch is in the AUTO position.
  2. The transmission range selector is not in the PARK position.

The BCM detect a short to voltage in the DRL relay control circuit.

The BCM will deactivate the DRL relay for the remainder of the ignition cycle.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the DRLs ON with a scan tool. The DRL Relay Command parameter should display On and the DRLs should illuminate.

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 23 and B+. If the test lamp illuminates, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  3. Install a 10 A fused jumper wire between the control circuit terminal 23 and ground. The DRLs should illuminate. If the DRLs do not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  4. If all circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
LED Dimming ControlB2610 0011
1. Interior Backlighting Malfunction

The body control module (BCM) supplies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the LED dimming control circuit illuminating the components listed below

  1. Radio
  2. Inflatable Restraint I/P Module Disable Switch
  3. Driver Information Center (DIC) Switch
  4. Steering Wheel Control Switches
  1. Ignition ON.
  2. The headlamps or park lamps are ON.

The BCM detects a short to ground on the LED dimming control circuit.

The BCM does not attempt to illuminate the LED lamps.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, cover the ambient light sensor, adjust 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 any component with inoperative incandescent dimming lighting.
  2. Ignition OFF, scan tool disconnected, 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.
  3. Connect a test lamp between the control circuit and ground.
  4. 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.
  5. If all circuits test normal, test or replace the component with the inoperative incandescent dimming lighting.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM or radio replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BCM Supply VoltageB2615 00B2615 00
Courtesy Lamp ControlB2615 0011
1. Courtesy Lamps Malfunction

Battery voltage for the courtesy lamps is supplied at all times, from the BCM 3 fuse located in the underhood fuse block, to the body control module (BCM). When the BCM receives a signal to command the courtesy lamps ON, it applies voltage through the courtesy lamps supply voltage circuits to the courtesy lamps listed below.

  1. The left and right I/P courtesy lamps
  2. Dome lamp
  1. Ignition ON.
  2. Courtesy lamps ON.

The BCM detects a short to ground on the courtesy lamp supply voltage circuit.

The BCM will deactivate the courtesy lamps.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the Courtesy Lamps ON and OFF with the scan tool. The interior courtesy lamps should turn ON and OFF when changing between commanded states.

  1. Ignition OFF, disconnect the harness connector at any component with inoperative incandescent dimming lighting.
  2. Ignition OFF, scan tool disconnected, 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.
  3. Connect a test lamp between the control circuit and ground.
  4. 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.
  5. If all circuits test normal, test or replace the component with the inoperative incandescent dimming lighting.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Dome Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Dome Lamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BCM Battery SupplyB2615 00B2615 00
Courtesy Lamp ControlB2615 0011
1. Courtesy Lamps Malfunction

Battery voltage for the courtesy lamps is supplied at all times, from the BCM 3 Fuse located in the underhood fuse block, to the body control module (BCM). When the BCM receives a signal to command the courtesy lamps ON, it applies voltage through the courtesy lamps relay control circuit in order to energize the relay. With the relay energized, battery voltage is applied through switch side of the relay and the courtesy lamp supply voltage circuits to the courtesy lamps listed below.

  1. Front dome lamp
  2. Rear dome lamp
  1. Ignition ON.
  2. Courtesy lamps ON.

The BCM detects a short to ground on the courtesy lamp PCB relay control circuit.

The BCM will deactivate the courtesy lamps.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the Courtesy Lamps ON and OFF with the scan tool. The interior courtesy lamps should turn ON and OFF when changing between commanded states.

  1. Ignition OFF, disconnect the harness connector at any component with inoperative incandescent dimming lighting.
  2. Ignition OFF, scan tool disconnected, 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.
  3. Connect a test lamp between the control circuit and ground.
  4. 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.
  5. If all circuits test normal, test or replace the component with the inoperative incandescent dimming lighting.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Body Wiring Harness Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
LED Dimming SupplyB2625 0021
1. Interior Backlighting Does Not Dim 2. Interior Backlighting Does Not Dim

The body control module (BCM) supplies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal then applies a pulse width modulated (PWM) voltage through the LED dimming supply circuit illuminating the HVAC control module to the requested level.

The ignition is ON.

The BCM detects a short to ground on the LED dimming supply circuit.

The BCM will not attempt to illuminate the LED indicator lamps.

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

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, cover the ambient light sensor, 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 any component with inoperative backlighting.
  2. Ignition OFF, scan tool disconnected, 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.
  3. Connect a test lamp between the control circuit and ground.
  4. 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.
  5. If all circuits test normal, test or replace the component with the inoperative backlighting.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM and HVAC control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
DRL Ambient Light Sensor SignalB2645 03B2645 07B2645 07
DRL Ambient Light Sensor GroundB2645 07

The ambient light sensor is used to monitor outside lighting conditions. The body control module (BCM) provides a 5 V reference signal to the ambient light sensor. The sensor is a variable resistor, it's resistance changes as outside lighting conditions change. With the headlamp switch in the AUTO position, the BCM monitors the sensor signal circuit to determine if the outside lighting conditions are correct for either daytime running lamps (DRL) or headlamp low beam operation. In daylight conditions, the BCM will command the DRLs ON. In low light conditions, the BCM will command the low beam headlamps ON.

  1. Ignition ON.
  2. The headlamp switch in the AUTO position.

B2645 03

The DTC will set when the BCM detects the ambient light sensor signal is below 0.196 V.

B2645 07

The DTC will set when the BCM detects the ambient light sensor signal is above 4.9 V.

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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, headlamp switch in the AUTO position, observe the scan tool Ambient Light Sensor parameter. The reading should be between 0.196-4.8 volts and change between day and night time conditions.

  1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
  2. Ignition OFF, test for less than 5.0 ohms between the low reference circuit terminal B and ground. If greater than the specified range, test the low reference circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 V. If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V. 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, test or replace the ambient light sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Daytime Running Lamp (DRL) Ambient Light Sensor Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BCM Supply VoltageB2652 00B2652 00
Instrument Panel Lamp ControlB2652 0011
1. Interior Backlighting Malfunction

The body control module (BCM) supplies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the instrument panel lamp supply voltage circuit illuminating the components listed below

  1. Headlamp Dimmer Switch
  2. Tow/Haul Switch
  3. Traction Control Switch
  4. HVAC Control Module
  5. Driver Window Switch
  6. Driver Door Lock Switch
  7. Auxiliary Blower Motor Switch
  8. Passenger Window Switch
  9. Passenger Door Lock Switch
  10. Auxiliary Front HVAC Control Assembly
  11. Auxiliary Rear HVAC Control Assembly
  1. Ignition ON.
  2. The headlamps or park lamps ON.

The BCM detects a short to ground on the instrument panel lamps supply voltage circuit.

The BCM does not attempt to illuminate the instrument panel lamps.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, park lamps ON, adjust the dimmer 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 any component with inoperative backlighting.
  2. Ignition OFF, scan tool disconnected, interior lamps OFF, doors CLOSED, test for less than 5 ohms between the ground circuit 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 and ground.
  4. 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.
  5. If all circuits test normal, test or replace the component with the inoperative backlighting.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Auxiliary Blower Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/manual-hvac-system/#hvac-system-manual)
  3. «Auxiliary Heater and Air Conditioning Control Replacement - Front»(/chevrolet/express-h1500/2013-2013/remont/manual-hvac-system/#hvac-system-manual)
  4. «Auxiliary Heater and Air Conditioning Control Replacement - Rear»(/chevrolet/express-h1500/2013-2013/remont/manual-hvac-system/#hvac-system-manual)
  5. «Front Side Door Window Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/heated-glassdefoggers/#fixed-and-moveable-window-system)
  6. «Door Lock Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/door-locks-anti-theft-systems/#power-door-lock-system-and-release-systems)
  7. «Heater and Air Conditioning Control Replacement»(/chevrolet/express-h1500/2013-2013/remont/manual-hvac-system/#hvac-system-manual)
  8. «Tow/Haul Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/automatic-trans/#automatic-transmission-4l60-e-m30-repair-instructions-on-vehicle)
  9. «Airbag Instrument Panel Module Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/airbag/#supplemental-inflatable-restraint-system)
  10. «Electronic Traction Control Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/anti-locktraction-control/#antilock-brake-system)
  11. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Center High Mounted Stop Lamp ControlB3445 0011
Center High Mounted Stop Lamp Ground1
1. Center High Mounted Stop Lamp Malfunction

Battery voltage is applied at all times to the body control module (BCM) from the BACKUP/STOP fuse located in the underhood fuse block. When the brake pedal is applied and the BCM receives a brake applied signal from the stop lamp switch. It then applies battery voltage through the CHMSL supply voltage circuit illuminating the CHMSL.

  1. Ignition ON.
  2. Brakes applied.

The BCM detects a short to ground on the CHMSL supply voltage circuit when the stop lamps are commanded ON.

The BCM will deactivate power to the CHMSL.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 4 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, connect the X4 harness connector at the BCM and disconnect the harness connector at the CHMSL.
  4. 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.
  5. Connect a test lamp between the control circuit terminal A and ground.
  6. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal. 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, test or replace the CHMSL.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «High Mount Stop Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+, BCM X3 Terminal 3B1395 03, B3600 03B1395 03, B3600 03
I/P Dimming Voltage ReferenceB1395 03, B3600 03B3600 03B1395 07
Stop Lamp Switch SignalB1395 03, B3600 0322
Instrument Panel Lamps Dimmer Switch SignalB3600 03B3600 031
1. Interior Backlighting Malfunction 2. Stop Lamps Malfunction

The instrument panel (I/P) dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The body control module (BCM) supplies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the I/P lamps supply voltage circuit and the LED dimming supply circuit to all related interior lamps, illuminating them to the desired level of brightness.

Ignition ON.

  1. The BCM detects a short to ground or open in the I/P dimming voltage reference circuit.
  2. The BCM detects a short to ground or open in the instrument panel lamps dimming signal circuit.

The I/P lamps are not illuminated.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

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.

  1. Ignition OFF, disconnect the X3 harness connector at the BCM.
  2. Ignition ON, 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.
  3. Ignition OFF, connect the X3 harness connector at the BCM and disconnect the harness connector at the headlamp switch.
  4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 15 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the BCM.
  5. Verify the scan tool Dimming Control Signal parameter is less than 0.2 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
  6. Install a 3A fused jumper wire between the signal circuit terminal 13 and the B+ circuit terminal 15. Verify the scan tool Dimming Control Signal parameter is greater than 2.75 volts. If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  7. Ignition OFF, disconnect the harness connector at the stop lamp switch.
  8. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  9. Install a 3A fused jumper wire between the signal circuit terminal D and the B+ circuit terminal C. Verify the scan tool Stop Lamp Switch Status parameter is 1023 Counts. If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.
  10. If all circuits test normal, replace the headlamp switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Stop Lamp Relay Coil ControlB3884 0011
1. Auxiliary Stop Lamps Malfunction

Battery voltage is applied at all times to the body control module (BCM) from the BCM 5 Fuse located in the underhood fuse block. When the brake pedal is applied, battery voltage is applied through the stop lamp switch and the stop lamp signal circuit to the BCM. The BCM then applies battery voltage through the stop lamp relay coil supply voltage circuit energizing the STOP LAMPS PCB Relay. With the relay energized, battery voltage is applied through the switch side of the relay and the control circuit to the auxiliary stop lamps.

  1. Ignition ON.
  2. Brakes applied.

The BCM detects a short to ground in the stop lamp relay coil supply voltage circuit when the stop lamps are commanded ON.

The BCM will deactivate power to the auxiliary stop lamps.

  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/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, press the brake pedal. The CHMSL should illuminate.

  1. Ignition OFF, disconnect the X5 harness connector at the BCM.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 5 and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Ignition ON, connect a 3 A fused jumper wire between the control circuit terminal 5 and B+. Verify the auxiliary stop lamps illuminate. If the stop lamps do not illuminate, test the 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Brake Position Sensor 5 V ReferenceC0277 06, C0890 03C0277 061
Brake Applied SignalC0297 00 and P0571 0033
Brake Position Sensor SignalC0277 06C0277 06C0277 07C0277 09
Center High Mounted Stop Lamp (CHMSL) Relay ControlB3884 0022
Left Rear Stop/Turn Lamp Control111
Right Rear Stop/Turn Lamp Control111
Brake Position Sensor Low ReferenceC0277 071
Center High Mounted Stop Lamp (CHMSL) Ground22
Left Rear Stop/Turn Lamp Ground11
Right Rear Stop/Turn Lamp Ground11
1. Stop Lamps Malfunction 2. Center High Mounted Stop Lamp (CHMSL) Malfunction 3. Cruise Control Malfunction

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5 V reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the right and left stop lamp control circuits, transmission control module (TCM), engine control module (ECM), and center high mounted stop lamp (CHMSL) control circuit.

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

DTC C0277 06 will set for the following conditions

  1. The BCM detects a short to ground or an open/high resistance in the brake pedal position sensor signal circuit.
  2. The BCM detects a short to ground or an open/high resistance in the brake pedal position sensor 5 V reference circuit.

DTC C0277 07 will set for the following conditions

  1. The BCM detects a short to battery voltage in the brake pedal position sensor signal circuit.
  2. The BCM detects an open/high resistance in the brake pedal position sensor low reference circuit.

C0277 09

The BCM detects the brake pedal position sensor signal is changing faster than possible under normal operating conditions.

C0277 4B

The brake pedal position sensor home position is not learned.

Actions Taken When the DTC Sets

  1. The Service Brake Assist indicator is commanded ON.
  2. If the DTC sets while the vehicle is running, the BCM will activate the brake lights when the vehicles transmission is not in the PARK position and the vehicle is not accelerating.
  3. For DTC C0277 4B the stop lamps may not activate at the expected brake pedal positions.
  1. The condition responsible for setting the DTC no longer exists.
  2. For DTC C0277 07 the ignition must be cycled before the code can be cleared.
  3. For DTC C0277 4B a successful brake pedal position sensor calibration has been performed.
  4. A history DTC will clear once 50 malfunction-free ignition cycles have occurred.
  5. A DTC will not clear the current status until the next ignition cycle.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

C0277 06 and C0277 07, C0890 03, and C0890 07

  1. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the low reference circuit terminal 1. If the test lamp does not illuminate, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 2 and ground. If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool BPP Sensor parameter is less than 100 counts. If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the BCM.
  5. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 2. Verify the scan tool BPP Sensor parameter is greater than 400 counts. If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, replace the brake pedal position sensor.

C0277 09

  1. Replace the brake pedal position sensor.
  2. Perform the brake pedal position sensor recalibration procedure. Refer to «Brake Pedal Position Sensor Calibration»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system__brake-pedal-position-sensor-calibration) .
  3. Operate the vehicle within the Conditions for Running and Setting the DTC and verify the DTC does not reset. If the DTC resets, replace the BCM.

C0277 4B

  1. Verify that the DTC sets under the Conditions for Running and Setting.
  2. Perform the brake pedal position sensor recalibration procedure. Refer to «Brake Pedal Position Sensor Calibration»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system__brake-pedal-position-sensor-calibration) .
  3. Operate the vehicle within the conditions that the customer experienced and verify the DTC does not reset. If the DTC resets, replace the brake pedal position sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Brake Pedal Position Sensor Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system__brake-pedal-position-sensor-replacement)
  2. «Brake Pedal Position Sensor Calibration»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system__brake-pedal-position-sensor-calibration)
  3. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Brake Position Sensor 5 V ReferenceC0277 06, C0890 03C0277 061
Brake Applied Signal Terminal 6 X5C0297 00 and P0571 0033
Brake Position Sensor SignalC0277 06C0277 06C0277 07C0277 09
Center High Mounted Stop Lamp (CHMSL) Relay ControlB3884 0022
Left Rear Stop/Turn Lamp Control111
Right Rear Stop/Turn Lamp Control111
Brake Position Sensor Low ReferenceC0277 071
Center High Mounted Stop Lamp (CHMSL) Ground22
Left Rear Stop/Turn Lamp Ground11
Right Rear Stop/Turn Lamp Ground11
1. Stop Lamps Malfunction 2. Center High Mounted Stop Lamp (CHMSL) Malfunction 3. Cruise Control Malfunction

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5 V reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the right and left stop lamp control circuits, transmission control module (TCM), engine control module (ECM), and center high mounted stop lamp (CHMSL) control circuit.

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

The BCM detects a short to ground in the brake applied signal circuit.

  1. The BCM stores the DTC to memory.
  2. The Service Brake Assist indicator is commanded ON.
  1. The condition responsible for setting the DTC no longer exists.
  2. A history DTC will clear once 50 malfunction-free ignition cycles have occurred.

Diagnostic Aids

Note. The 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 .

Verify that the brake pedal position sensor is properly calibrated.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the X1 harness connector at the ECM.
  2. Connect a test lamp between the appropriate signal circuit terminal listed below and ground: Terminal 9 - without LU3 Terminal 55 - with LU3
  3. Ignition ON, turn 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 selected states. If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, replace the ECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Brake Pedal Position Sensor Calibration»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system__brake-pedal-position-sensor-calibration)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM or ECM replacement, setup, and programming

Symptoms - Lighting

Note. The following steps must be completed before doing the Symptom tables.

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) . No DTCs are 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/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) «Interior Lighting Systems Description and Operation»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the lighting system. Refer to «Checking Aftermarket Accessories»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__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»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Courtesy Lamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Daytime Running Lamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Hazard Lamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  5. «Headlamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  6. «Interior Backlighting Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  7. «Park, License, and/or Tail Lamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  8. «Stop Lamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  9. «Turn Signal Lamps and/or Indicators Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Backup Lamps PCB Relay B+11
T/LAMP - BCK/UP Lamp Fuse111
AUX/TRLR - BCK/UP Lamp Fuse111
Backup Lamps PCB Relay ControlB2545 0011
Backup Lamps Control111
Backup Lamps PCB Relay Ground1
Backup Lamps Ground1
1. Backup Lamps Malfunction

Battery voltage is applied at all times to the backup lamp PCB relay which is an internal part of the body fuse block. When the PRNDL is placed in the REVERSE position, a signal is sent from the transmission control module (TCM) to the body control module (BCM). The BCM then applies battery voltage to the backup lamp relay control circuit energizing the relay. With the relay energized, battery voltage is applied through the switch side of the relay, the T/LAMP BCK/UP fuse, and the backup lamp supply voltage circuit to the left and right backup lamps. Or, the AUX/TRLR BCK/UP fuse and the supply voltage circuit to the backup alarm and the trailer connector. The engine may need to be running for the backup lamps to function.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__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 backup lamps should turn ON and OFF when changing between the commanded states.

  1. Ignition OFF, disconnect the X1 harness connector at the body fuse block.
  2. Test for less than 5 ohms between the ground circuit terminal E2 and ground. If greater then the specified range, test the ground circuit for and open/high resistance.
  3. Connect a test lamp between the control circuit terminal K8 and ground.
  4. 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. 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. Ignition OFF, disconnect the appropriate backup lamp.
  6. Test for less than 5 ohms between the ground circuit terminal G and ground. If greater than the specified range, test the ground circuit for a open/high resistance.
  7. Connect a test lamp between the control circuit terminal A and ground.
  8. Command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF between the commanded states. If the test lamp is always ON, test the control circuit for short to voltage. If the test lamp is always OFF, test the control circuit for a short to ground or and open/high resistance.
  9. If the circuits test normal, replace the body fuse block.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Backup Lamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Backup Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Body Wiring Harness Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  4. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+, BCM X4 Terminal 2B2615 00B2615 00
B+, BCM X3 Terminal 2B1480 00B1480 00
B+, BCM X2 Terminal 2B2652 00B2652 00
12 Volt ReferenceB1395 00, B3600 03B3600 03
Courtesy Lamp Supply VoltageB2615 0012
Inadvertent Power Courtesy LampB1480 006
Courtesy Lamp On Switch Signal211*
Instrument Panel Lamps Dimmer Switch SignalB3600 03B3600 039
Interior Lamp Defeat Switch Signal11010
LED Backlight Dimming ControlB2610 0078
Instrument Panel Lamp Dimming ControlB2652 0078
Driver Door Open Switch Signal243
Passenger Door Open Switch Signal255
Ground - Courtesy Lamp1
Ground - Driver Door Lock4
Ground - Inadvertent Courtesy Lamps6
Ground - Passenger Door Lock5
* Internal damage to the switch may occur if shorted to B+ 1. Courtesy lamps are inoperative 2. Courtesy lamps are always On 3. Dome Lamp Switch Malfunction 4. Courtesy lamp control malfunction - driver door 5. Courtesy lamp control malfunction - passenger door 6. Inadvertent power courtesy lamps inoperative 7. Interior backlighting inoperative 8. Interior backlighting always On 9. Interior backlighting will not dim 10. Courtesy lamp defeat switch malfunction

The BCM 3 fuse, located in the underhood fuse block, supplies battery voltage to the body control module (BCM). The BCM applies this voltage to the courtesy lamps through the courtesy lamp supply voltage circuit. When any door is opened, the door open switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input, the BCM will activate the courtesy lamp supply voltage circuit, providing battery voltage to the dome lamp and instrument panel (I/P) courtesy lamps. The courtesy lamps can be manually activated by placing the interior lamp switch in the DOME position.

Inadvertent power courtesy lamp feature provides a similar function for the interior lamps as a retained accessory power feature. The BCM will energize the courtesy lamps supply voltage circuit when the BCM is in the active state (awake). When the inadvertent power courtesy lamps supply voltage circuit is energized, it supplies voltage from the BCM 2 fuse located in the underhood fuse block, to all the interior lights listed below. The BCM will continue to supply voltage to the interior lamps after the ignition is turned OFF so that the interior lamps may be operated.

  1. Front Dome/Reading Lamp
  2. Middle Dome/Reading Lamp
  3. Rear Dome/Reading Lamp
  4. Sunshade Mirror Lamps
  5. Underhood Lamp

In the event that any of these lamps were to remain illuminated for a period of more than 20 minutes with the ignition switch in the OFF position and no BCM input activity, the BCM will deactivate the inadvertent power supply voltage circuit to prevent a total battery discharge condition.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Driver Door Ajar Sw. and Passenger Door Ajar Sw. parameters while opening and closing each vehicle door. The parameters should change between Door Ajar and Door Closed. If the parameter does not change between the selected states, refer to «Door Ajar Indicator Malfunction»(/chevrolet/express-h1500/2013-2013/remont/door-locks-anti-theft-systems/#power-door-lock-system-and-release-systems) .
  2. Observe the scan tool Rear Closure Ajar Sw. parameter while opening and closing the rear closure door. The parameter should change between Active and Inactive. If the parameter does not change between the selected states, refer to «Cargo Door Ajar Indicator Malfunction»(/chevrolet/express-h1500/2013-2013/remont/door-locks-anti-theft-systems/#power-door-lock-system-and-release-systems) .
  3. All doors closed, observe the scan tool 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 Lamp Switch Malfunction.
  4. Command the Courtesy Lamp ON and OFF with a scan tool. The courtesy lamps should turn ON and OFF when changing between the commanded states. If the courtesy lamps do not turn ON and OFF when commanded, refer to Courtesy Lamp Malfunction.
  5. Turn the individual reading lamps ON and OFF with their respective switches. The reading lamps should turn ON and OFF when changing between the selected states. If any reading lamp does not turn ON and OFF when selected, refer to Inadvertent Power Courtesy Lamps Malfunction below.
  6. Turn the left and right sunshade lamps ON and OFF with their respective switches. The sunshade lamps should turn ON and OFF when changing between the selected states. If any reading lamp does not turn ON and OFF when selected, refer to Inadvertent Power Courtesy Lamps Malfunction below.
  7. Turn the underhood lamp ON and OFF by opening and closing the hood. The underhood lamp should turn ON and OFF when changing between the selected states. If the rear compartment courtesy lamp does not turn ON and OFF when selected, refer to Inadvertent Power Courtesy Lamps Malfunction below.

Dome Lamp 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 with all doors closed, verify the scan tool Ctsy. Lamp Actv. Reason parameter is Off. If not the specified value, test the signal circuits listed below for a short to ground. If the circuits test normal, replace the BCM. Terminal 9 Terminal 12
  4. Install a 3 A fused jumper wire between the signal circuit terminal 12 and ground. 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 3 A fused jumper wire between the signal circuit terminal 9 and ground. 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 and panel dimmer switch.

Courtesy Lamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate dome lamp.
  2. Verify that a test lamp illuminates between the ground circuit terminal B and B+. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit terminal A and ground.
  4. Command the 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 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 dome lamp.

Inadvertent Power Courtesy Lamps Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate courtesy lamp.
  2. Verify that a test lamp illuminates between the ground circuit terminal B and B+. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between the appropriate B+ circuit terminal listed below and ground. Courtesy/Reading Lamp - terminal C Sunshade Lamp - terminal A Underhood Lamp - terminal A If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the courtesy lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Sunshade Illuminated Mirror Lamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Dome Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Dome Lamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  5. «Underhood Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  6. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
DRL Relay B+11
DRL Ambient Light Sensor SignalB2645 03B2645 07B2645 07
DRL Relay Control11B2600 00
Low Beam Headlamp Control222
DRL Ambient Light Sensor GroundB2645 07
Low Beam Headlamp Ground2
1. Daytime Running Lamps Malfunction 2. Headlamp Malfunction - Low Beam

The ambient light sensor is a light sensitive transistor that varies the voltage signal to the body control module (BCM) based on outside lighting conditions. When the ambient light sensor indicates daytime conditions with the transmission in gear, the body control module (BCM) grounds the DRL relay control circuit, energizing the DRL relay. With the DRL relay energized, voltage is applied through the relay switch contacts, the DRL 1 fuse, and the DRL 2 fuse to the left and right low beam headlamps. Any function or condition that turns the headlamps ON will cancel DRL operation.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, headlamps OFF, command the Low Beams ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when changing between the commanded states. If the low beam headlamps do not change between the commanded states, refer to «Headlamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  2. Command the DRLs ON and OFF with a scan tool. The daytime running lamps should turn ON and OFF when changing between the commanded states. If the daytime running lamps do not change between the commanded states, refer to «Daytime Running Lamps Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  3. Observe the scan tool Ambient Light Status parameter while supplying sufficient light to simulate daylight conditions to the ambient light sensor. After 30 seconds, the parameter should be Day. If not the specified value, refer to «Ambient Light Sensor Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .

Daytime Running Lamps Malfunction

  1. Ignition OFF, disconnect the X3 harness connector at the fuse block - underhood.
  2. Connect a test lamp between the control circuit terminal H5 and B+.
  3. Command the DRLs 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 X3 harness connector at the fuse block - underhood. Disconnect the harness connector at the headlamp.
  5. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohms between the headlamp ground circuit terminal listed below and ground. Terminal B (with V22) Terminal A (without V22) 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 listed below and ground. Terminal A (with V22) Terminal C (without V22)
  7. Command the DRLs 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 fuse block - underhood. 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, test or replace the fuse block - underhood. 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, test or replace the headlamp.
  8. If all circuits test normal, test or replace the headlamp.

Ambient Light Sensor Malfunction

  1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
  2. Ignition OFF, 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 the scan tool Ambient Light Sensor parameter is greater than 4.65 V. If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM
  4. Install a 3 A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool Ambient Light Sensor parameter is less than 1.96 V. 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. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Daytime Running Lamp (DRL) Ambient Light Sensor Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Headlamp Replacement (V22)»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Headlamp Capsule Replacement (Minus V22)»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  5. «Headlamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  6. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Hazard Switch Signal222
Turn Signal Control111
Turn Signal/Multifunction Switch Ground2
Turn Signal Lamp Ground1
1. Hazard Lamps Malfunction 2. Turn Signal/Multifunction Switch Malfunction

The body control module (BCM) controls the hazard lamps based on inputs from the hazard switch. With the hazard switch closed, a ground path is provided on the hazards switch signal circuit, indicating a hazard lamp request. When this request is seen, the BCM will pulse the turn signal lamp supply voltage circuits, illuminating the turn signal lamps.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Hazard Lamp Switch parameter while turning the hazard lamp switch ON and OFF. The reading should change between Active and Inactive. If the parameter does not change between the commanded states, refer to «Circuit/System Testing»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  2. Observe the right and left turn signal lamps while turning the hazard lamp switch ON and OFF. The right and left turn signal lamps should flash ON and OFF while the hazard lamp switch is ON and remain OFF when the hazard lamp switch is OFF. If the turn signal lamps do not cycle between the selected states, refer to «Turn Signal Lamps and/or Indicators Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  3. Command the Lamp Test ON and OFF with a scan tool. The left and right turn signal indicators should turn ON and OFF when changing between the commanded states. If the left and right turn signal indicators illuminate during the test, replace the BCM. If the left and right turn signal indicators do not illuminate during the test or remain illuminated at all times, replace the instrument cluster.
  1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
  2. Test for less than 5 ohms between the ground circuit terminal C and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Test for less than 5 ohms between the ground circuit terminal F and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. 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.
  5. Install a 3 A 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 and open/high resistance. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, replace the turn signal/multifunction switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Turn Signal Multifunction Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/steering-column-switches/#steering-wheel-and-steering-column)
  2. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Flash to Pass Switch Signal444
Headlamp Dimmer Switch High Beam Signal444
Headlamp Switch Headlamps Off SignalB257A 0033*
Headlamp Switch Headlamps On SignalB257A 0033*
Park Lamp Switch On SignalB257A 00B257A 00B257A 00*
High Beam Headlamp Control222
High Beam Relay Control22B2580 00
Low Beam Headlamp Control111
Low Beam Relay Control11B2575 00
Low Beam Headlamp Ground1
High Beam Headlamp Ground2
Headlamp Switch Ground3
Turn Signal/Multifunction Switch Ground4
* Internal damage to the headlamp switch may occur if shorted to B+ 1. Headlamp Malfunction - Low Beam 2. Headlamp Malfunction - High Beam 3. Headlamp Switch Malfunction 4. Dimmer Switch Malfunction

The vehicle headlamps are controlled by the body control module (BCM) based on inputs from the headlamp switch and the turn signal/multifunction switch. The headlamp switch has four positions: Off, Auto, Park, and Headlamps. The default headlamp switch position is the Auto position, which the BCM uses the ambient light sensor to determine when headlamps are needed. The Off position of the headlamp switch is a momentary switch that overrides the automatic headlamps and turns off the vehicle headlamps. When the headlamp switch is in the Park position, the park lamp switch signal circuit is pulled low signaling the BCM to illuminate the vehicle parking lamps. With the headlamp switch in the Headlamps ON position, the headlamp switch ON signal circuit and the park lamp switch signal are both pulled low signaling the BCM to illuminate the headlamps and the tail/park lamps.

The headlamp high beams are controlled through the headlamp dimmer switch and the flash to pass switch, both located in the turn signal/multifunction switch. The flash to pass switch is a momentary type switch, designed to illuminate the high beams as long as the switch is held. With the switch closed, the flash to pass switch signal circuit is grounded, prompting the BCM to turn on the high beam lamps. The headlamp dimmer switch allows the operator to select between full time high or low beam operation. Unlike the flash to pass switch, it is not a momentary switch. When the headlamp dimmer switch is in the high beam position, the headlamp dimmer switch high beam signal circuit is grounded. This signals the BCM to turn on the high beam headlamps.

The BCM controls the headlamps based on the inputs explained above. When a low beam request is received, the BCM grounds the headlamp low beam relay control circuit energizing the LOW BEAM PCB Relay. With the low beam relay energized, B+ is applied through the switch side of the relay, both LO BEAM fuses, and the low beam supply voltage circuits illuminating the low beam headlamps. When a high beam request is received, the BCM grounds the headlamp high beam relay control circuit energizing the HIGH BEAM PCB Relay. With the high beam relay energized, B+ is applied through the switch side of the relay, both HI BEAM fuses, and the high beam supply voltage circuits illuminating the high beam headlamps.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Auto Hdlp. Disable Sw. parameter while turning the headlamp switch between the OFF, Auto and Park positions. The reading should change between Active and Inactive. If the reading does not change between the specified values, refer to «Headlamp Switch Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  2. With the headlamps ON, observe the scan tool Flash to Pass Switch parameter while applying and releasing the turn signal/multifunction switch. The reading should change between Active and Inactive. If the reading does not change between the specified values, refer to «Turn Signal/Multifunction Switch Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  3. Observe the scan tool High Beam Select Switch parameter while switching the turn signal/multifunction switch between the low and high beam positions. The reading should change between Active and Inactive. If the reading does not change between the specified values, refer to «Turn Signal/Multifunction Switch Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  4. 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 as commanded, refer to «Headlamps Malfunction - Low Beam»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  5. Command the High Beams ON and OFF with a scan tool. The high beam headlamps should turn ON and OFF when commanded. If the high beam headlamps do not turn ON and OFF as commanded, refer to «Headlamps Malfunction - Low Beam»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  6. Command the Lamp Test ON and OFF with a scan tool. The high beam indicator should turn ON and OFF when changing between the commanded states. If the high beam indicator illuminates during the test, replace the BCM. If the high beam indicator does not illuminate during the test or remain illuminated at all times, replace the instrument cluster.

Headlamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer 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 Auto Hdlp. Disable Sw. parameter is Inactive. If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Ignition ON, verify the scan tool Headlamp ON Switch parameter is Inactive. If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the BCM.
  5. 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.
  6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Parklamp 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. Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Parklamp 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.
  8. Install a 3 A fused jumper wires 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 terminal 1 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  9. If all circuits test normal, replace the headlamp and panel dimmer switch.

Turn Signal/Multifunction Switch Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the turn signal/multifunction switch.
  2. Test for less than 5 ohms between the ground circuit terminal D and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Flash to Pass 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. Ignition ON, verify the scan tool High Beam Select Switch parameter is Inactive. If not the specified value, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3 A fused jumper wire between the signal circuit terminal E 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 and open/high resistance. If the circuit tests normal, replace the BCM.
  6. Install a 3 A fused jumper wire between the signal circuit terminal C 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 and 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.

Headlamp Malfunction - Low Beam

  1. Ignition OFF, disconnect the X3 harness connector at the underhood fuse block.
  2. Connect a test lamp between the relay control circuit terminal H4 and ground.
  3. Ignition ON, command the Low Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF 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 X3 harness connector at the underhood fuse block.
  5. Ignition OFF, disconnect the harness connector at the appropriate low beam headlamp.
  6. Test for less than 5 ohms between the ground circuit terminal listed below and ground. Terminal B - with V22 Terminal A - w/o V22 If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect a test lamp between the appropriate control circuit terminal listed below and ground. Terminal A - with V22 Terminal C - w/o V22
  8. Ignition ON, command the Low Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF 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, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  9. If all circuits test normal, test or replace the low beam headlamp.

Headlamp Malfunction - High Beam

  1. Ignition OFF, disconnect the X3 harness connector at the underhood fuse block.
  2. Connect a test lamp between the relay control circuit terminal K8 and ground.
  3. Ignition ON, command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF 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 X3 harness connector at the underhood fuse block.
  5. Ignition OFF, disconnect the harness connector at the appropriate high beam headlamp.
  6. Test for less than 5 ohms between the ground circuit terminal listed below and ground. Terminal B - with V22 Terminal A - w/o V22 If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect a test lamp between the control circuit terminal listed below and ground. Terminal A - with V22 Terminal B - w/o V22
  8. Ignition ON, command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF 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, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  9. If all circuits test normal, test or replace the high beam headlamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Replacement (V22)»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Headlamp Capsule Replacement (Minus V22)»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Headlamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  5. «Turn Signal Multifunction Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/steering-column-switches/#steering-wheel-and-steering-column)
  6. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  7. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+, BCM X2 terminal 2B2652 00B2652 00
I/P Dimming 12 V ReferenceB1395 03, B3600 03B1395 03, B3600 03
Instrument Panel Lamp Dimming ControlB2652 0023
LED Backlighting Dimming ControlB2610 0045
Instrument Panel Lamp Dimmer Switch SignalB3600 03B3600 031
Ground - Headlamp Switch1
1. Headlamps And Dimmer Switch Malfunction 2. Incandescent Dimming Lamps Are Inoperative 3. Incandescent Dimming Lamps Are Always On 4. Led Backlighting Is Inoperative 5. Led Backlighting Is Always On

The body control module (BCM) supplies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the instrument panel lamp dimming control circuit and the LED backlighting dimming control circuit illuminating all backlighting lamps.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Dimming Control Signal parameter while operating the dimmer switch from low to high. The parameter should move between high and low when the dimmer switch is moved up and down. If the parameter does not change between the selected states, refer to «Dimmer Switch Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .
  2. Command the Incandescent Dimming and LED Dimming ON and OFF with a scan tool. The backlit dimming components should turn ON and OFF when changing between the commanded states. If the LED backlighting components do not change between the commanded states, refer to «Interior Backlighting Malfunction»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system) .

Dimmer Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer 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, test for 11.8-12.2 V between the 12 V reference circuit terminal 15 and ground. If less than the specified value, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Ignition ON, verify the scan tool Dimming Control Signal parameter is less than 0.2 V. 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.
  5. Install a 3 A fused jumper wire between the signal circuit terminal 13 and the 12 V reference circuit terminal 15. Verify the scan tool Dimming Control Signal parameter is greater than 2.75 V. 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 any component with inoperative backlighting.
  2. Ignition OFF, scan tool disconnected, 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.
  3. Connect a test lamp between the control circuit and ground.
  4. Command the Incandescent Dimming or 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.
  5. If all circuits test normal, test or replace the component with the inoperative backlighting.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Front Side Door Window Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/heated-glassdefoggers/#fixed-and-moveable-window-system)
  3. «Door Lock Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/door-locks-anti-theft-systems/#power-door-lock-system-and-release-systems)
  4. «Heater and Air Conditioning Control Replacement»(/chevrolet/express-h1500/2013-2013/remont/manual-hvac-system/#hvac-system-manual)
  5. «Auxiliary Heater and Air Conditioning Control Replacement - Front»(/chevrolet/express-h1500/2013-2013/remont/manual-hvac-system/#hvac-system-manual)
  6. «Auxiliary Heater and Air Conditioning Control Replacement - Rear»(/chevrolet/express-h1500/2013-2013/remont/manual-hvac-system/#hvac-system-manual)
  7. «Steering Wheel Control Switch Assembly Replacement»(/chevrolet/express-h1500/2013-2013/remont/memory-modules/#secondary-and-configurable-customer-control-system)
  8. «Driver Information Display Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges)
  9. «Control Module References»(/chevrolet/express-h1500/2013-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM, HVAC, IPC, or Radio replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__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 SignalB257A 00B257A 00B257A 00*
Park Lamp Relay Control11B2585 00
Park Lamp Control111
Left Front Park/Turn Signal Lamp Ground1
Left Marker Lamp Ground1
License Lamp Ground1
Right Marker Lamp Ground1
Right Front Park/Turn Signal Lamp Ground1
Left Rear Park Lamp Ground1
Right Rear Park Lamp Ground1
Headlamp Switch Ground2
* Internal damage to the headlamp switch may occur if shorted to B+ 1. Park Lamp Malfunction 2. Park Lamp Switch Ground

The vehicle park, license, and tail lamps are controlled by the body control module (BCM) based on an input from the headlamp switch. The headlamp switch has four positions: Off, Auto, Park, and Headlamps. The default headlamp switch position is Auto, which the BCM uses the ambient light sensor to determine when exterior lamps are needed. The Off portion of the headlamp switch is a momentary switch which overrides the automatic lamps and will turn off the vehicle lamps. The Park position of the headlamp switch will only illuminate the vehicle parking lamps. The Headlamp position of the headlamp switch will illuminate both the parking lamps, as well has the headlamps. With the headlamp switch in the Park position, the park lamp switch signal circuit is grounded, prompting the BCM to turn on the exterior lamps, regardless of other factors such as ambient light.

When a park lamp request is received, the BCM grounds the park lamp relay control circuit. This energizes the PRK LAMP Relay and battery voltage is applied through the switch side of the relay, the exterior lamp fuses, and the supply voltage circuits illuminating the front park, license, tail, and marker lamps.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Park Lamp Switch parameter while cycling the park lamp switch ON and OFF. The readings should toggle between Active and Inactive. If the readings do not change between the commanded states, refer to Park Lamp Switch Malfunction below.
  2. Ignition ON, command the Parking Lamps ON and OFF with a scan tool. The park, license, and marker lamps should turn ON and OFF when changing between the commanded states. If the lamps do not turn ON and OFF when changing between the commanded states, refer to Park Lamp Malfunction below.

Park Lamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
  2. Test for less than 5 ohms between the ground circuit terminal 8 and ground. If greater than the specified value, 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 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Parklamp Switch parameter is Active. If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the headlamp and panel dimmer switch.

Park Lamp Malfunction

  1. Ignition OFF, disconnect the PRK 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 85 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the fog lamp relay.
  4. 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 an open/high resistance.
  5. Disconnect the harness connector at the appropriate park lamp.
  6. Test for less than 5 ohms between the park lamp ground circuit terminal listed below and ground: Tail/Stop and Turn Signal Lamp - Terminal G License Lamp - Terminal B Park/Turn Signal Lamp - Terminal C Marker Lamp - Terminal B If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the park lamp.
  8. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park lamp is activated. If the park lamp does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the park lamp. If the park lamp does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the park lamp.
  9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  10. 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.
  11. If all circuits test normal, test or replace the PRK LAMP relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Headlamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  2. «Headlamp Bulb Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Parking and Turn Signal Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Tail Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  5. «Rear License Plate Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  6. «Relay Replacement (Within an Electrical Center)»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions) , «Relay Replacement (Attached to Wire Harness)»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  7. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
I/P Voltage Reference - Stop Lamp SwitchB1395 03, B3600 032
Stop Lamp Switch SignalB1395 03, B3600 0322
CHMSL ControlB3445 0011
Left Rear Stop/Turn Lamp Control111
Right Rear Stop/Turn Lamp Control111
Stop Lamp Relay ControlB3884 0011
Center High Mounted Stop Lamp (CHMSL) Ground1
Left Rear Stop/Turn Lamp Ground1
Right Rear Stop/Turn Lamp Ground1
Stop Lamp Relay Ground1
1. Stop Lamp Malfunction 2. Stop Lamp Switch Malfunction

The body control module (BCM) controls the stop lamps based on the input from the stop lamp switch. When the BCM detects the brake pedal is depressed, B+ is applied to the stop lamp relay control circuit energizing the Stop Lamp PCB Relay. With the relay energized, B+ is applied to the stop/turn lamp supply voltage circuits illuminating both stop lamps. At the same time the BCM applies B+ to the center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM).

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Stop Lamp Switch Status parameter while pressing and releasing the brake pedal. The parameter should change between 1023 Counts and 1 Count. If the parameter does not change between the commanded states, refer to Stop Lamp Switch Malfunction below.
  2. 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 or right stop lamps do not change between the selected states, refer to the Stop Lamp Malfunction below.
  3. Observe the center high mount stop lamp while pressing and releasing the brake pedal. The center high mount stop lamp should turn ON and OFF. If the center high mount stop lamp does not change between the selected states, refer to Center High Mount Stop Lamp Malfunction below.

Stop Lamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
  2. Verify that a test lamp illuminates between the 12 V reference circuit terminal C and ground. If the test lamp does not illuminate, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  3. Ignition ON, verify the scan tool Stop Lamp Switch Status parameter reading is 1 Count. If greater than the specified value, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the BCM.
  4. Connect a 3 A fused jumper wire between the signal circuit terminal D and the 12 V reference circuit terminal C. Verify the scan tool Stop Lamp Switch Status parameter is 1023 Counts. If not the specified value, test the signal 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 stop lamp switch.

Stop Lamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate stop lamp.
  2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal G 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 ground.
  4. Turn the stop lamps ON and OFF by pressing and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the selected 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, test or replace the stop lamp.

Center High Mount Stop Lamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the center high mount stop lamp.
  2. Ignition 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.
  3. Connect a test lamp between the control circuit terminal A and the ground.
  4. Ignition ON, apply and release the brake pedal. The test lamp should turn ON and OFF as the brake pedal is applied and released. 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 center high mount stop lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Stop Lamp Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system__stop-lamp-switch-replacement)
  2. «Tail Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «High Mount Stop Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Underhood Electrical Center or Junction Block Replacement»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  5. «Control Module References»(/chevrolet/express-h1500/2013-2013/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/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-h1500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+ - BCM X4 Terminal 1B2615 00, 5B2615 00, 5
B+ - BCM X4 Terminal 222
B+ - BCM X4 Terminal 377
Left Front Turn Signal Lamp Supply Voltage244
Right Front Turn Signal Lamp Supply VoltageB2615 00, 555
Left Rear Stop/Turn Lamp Supply Voltage266
Right Rear Stop/Turn Lamp Supply Voltage777
Left Turn Signal Switch Signal222*
Right Turn Signal Switch Signal333*
Ground - Turn Signal/Multifunction Switch11
Ground - LF Park/Turn Signal Lamp44
Ground - RF Park/Turn Signal Lamp55
Ground - Left Tail/Stop and Turn Signal Lamp66
Ground - Right Tail/Stop and Turn Signal Lamp77
* Internal damage to the turn signal/multifunction switch may occur if shorted to B+ 1. All Turn Signals Inoperative 2. Left Turn Signals Malfunction 3. Right Turn Signals Malfunction 4. Left Front Turn Signal Malfunction 5. Right Front Turn Signal Malfunction 6. Left Rear Turn Signal Malfunction 7. Right Rear turn Signal Malfunction

Ground is applied at all times 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 left or right turn position, ground is applied through the respective left or right turn signal switch signal circuit to the body control module (BCM). The BCM then applies a pulsating voltage to the front and rear turn signal lamps through there respective voltage supply circuits. At the same time, the BCM sends a serial data message to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-h1500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON, observe the scan tool Right Turn Signal Switch and Left Turn Signal Switch parameters while cycling the turn signal switch between the right and left positions. The readings should change between Active and Inactive. If the parameters do not change between the selected states, refer to Turn Signal/Multifunction Switch Malfunction below.
  2. Ignition ON, observe the right and left turn signal lamps while cycling the turn signal switch between the right and left positions. Verify the turn signal lamps turn ON and OFF. If the turn signal lamps do not cycle between the selected states, refer to Turn Signal Lamps Malfunction below.
  3. Command the Lamp Test ON and OFF with a scan tool. The left and right turn signal indicators should turn ON and OFF when changing between the commanded states. If the left and right turn signal indicators illuminate during the test, replace the BCM. If the left and right turn signal indicators do not illuminate during the test or remain illuminated at all times, replace the instrument cluster.

Turn Signal/Multifunction Switch Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
  2. Verify that a test lamp illuminates between the ground circuit terminal F 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 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. Connect a 3 A 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 and open/high resistance. If the circuit tests normal, replace the BCM.
  6. Connect a 3 A 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 and 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 connect at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminals listed below and ground. B+ terminal 1 B+ terminal 2 B+ terminal 3 If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuits test normal and the circuit fuse is open, test the appropriate control circuit terminal(s) listed below for a short to ground. Terminal 5 X4 for an open BCM 3 fuse Terminal 1 X5 and terminal 4 X5 for an open BCM 5 fuse Terminal 2 X5 for an open BCM 6 fuse
  3. Ignition OFF, reconnect the X4 harness connector at the BCM.
  4. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
  5. Test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground. Front Turn Signal terminal C Outside Rearview Mirror terminal D Rear Turn Signal terminal G If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the appropriate control circuit terminal listed below and ground. Front Turn Signal terminal A Outside Rearview Mirror terminal B Rear Turn Signal terminal A
  7. Ignition ON, command the appropriate turn signal 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.
  8. If all circuits test normal, test or replace the turn signal bulb.

Turn Signal/Multifunction Switch

  1. Ignition OFF, disconnect the harness connector X1 at the turn signal/multifunction switch.
  2. Test for infinite resistance between the terminals listed below and the ground circuit terminal F with the switch in the neutral position. Signal terminal D Signal terminal E If not the specified value, replace the turn signal/multifunction switch.
  3. Test for less than 2.0 ohms between the signal terminal E and the ground terminal F with the switch in the left turn position. If greater than the specified range, replace the turn signal/multifunction switch.
  4. Test for less than 2.0 ohms between the signal terminal D and the ground circuit terminal F with the switch in the right turn position. If greater than the specified range, replace the turn signal/multifunction switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Turn Signal Multifunction Switch Replacement»(/chevrolet/express-h1500/2013-2013/remont/steering-column-switches/#steering-wheel-and-steering-column)
  2. «Parking and Turn Signal Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  3. «Tail Lamp Replacement»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system)
  4. «Control Module References»(/chevrolet/express-h1500/2013-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM and IPC replacement, setup, and programming

Stop Lamp Switch Replacement

Note. Brake system may use a brake switch, stoplight switch or brakelight switch. System may instead use a Brake Pedal Position Sensor to control these functions.

Removal Procedure

  1. Disconnect the battery negative cable. Refer to «Battery Negative Cable Disconnection and Connection»(/chevrolet/express-h1500/2013-2013/remont/charging-system/#battery-charging-system-and-starting-system) .
  2. Disconnect the electrical connector from the stop lamp switch.
  3. Remove the retainer from the brake pedal pin.
  4. Remove the stop lamp switch and the pushrod to the power brake booster from the brake pedal pin.
  5. Unsnap the stop lamp switch from the power brake booster pushrod.

Installation Procedure

  1. Snap the stop lamp switch onto the pushrod to the power brake booster.
  2. Install the stop lamp switch with the pushrod on the brake pedal pin.
  3. Install brake switch retainer.
  4. Connect the electrical connector to the stop lamp switch.
  5. Connect the battery negative cable. Refer to «Battery Negative Cable Disconnection and Connection»(/chevrolet/express-h1500/2013-2013/remont/charging-system/#battery-charging-system-and-starting-system) .

Brake Pedal Position Sensor Replacement

Note. Brake system may use a brake switch, stoplight switch or brakelight switch. System may instead use a Brake Pedal Position Sensor to control these functions.

Scheme 14

Scheme 14: Removal Procedure
Scheme 14: Removal Procedure
  1. Place the ignition switch in the OFF position.
  2. Disconnect the brake pedal position sensor electrical connector.
  3. Remove the brake pedal position sensor bolt (1).
  4. Remove the brake pedal position sensor (1.
  1. Install the brake pedal position sensor (1.
  2. Install the brake pedal position sensor bolt (1).
  3. Connect the brake pedal position sensor electrical connector.
  4. Calibrate the brake pedal position sensor. Refer to «Brake Pedal Position Sensor Calibration»(/chevrolet/express-h1500/2013-2013/remont/exterior-lights/#lighting-system__brake-pedal-position-sensor-calibration) .

Brake Pedal Position Sensor Calibration

Note. Brake system may use a brake switch, stoplight switch or brakelight switch. System may instead use a Brake Pedal Position Sensor to control these functions.

Calibration Criteria

IMPORTANTDo not apply the brake pedal during the brake pedal position sensor calibration procedure. Any movement of the brake pedal during this procedure will cause the calibration procedure to fail. If this occurs, the brake pedal position sensor (BPPS) calibration must be repeated.

Brake pedal position sensor calibration must be performed after the brake pedal position sensor or body control module (BCM) have been serviced. The calibration procedure will set the brake pedal position sensor home value. This value is used by the BCM to determine the action of the driver applying the brake system and to provide this information to the vehicle subsystems via the GMLAN communication bus.

Calibration Procedure

  1. Apply the parking brake.
  2. Place the transmission in the PARK position.
  3. Install a scan tool.
  4. Clear all BCM DTCs before proceeding.
  5. Navigate to the Vehicle Control Systems menu.
  6. Select Module Setup menu item.
  7. Select BCM menu item.
  8. Select the BPP Sensor Calibration procedure and follow the directions displayed on the screen.

Scheme 15

Scheme 15: Headlamp Switch Replacement
Scheme 15: Headlamp Switch Replacement
CalloutComponent Name
1Instrument Panel Cluster Trim Plate Bezel Assembly Refer to Instrument Panel Cluster Trim Plate Bezel Replacement .
2Headlamp Switch Assembly Procedure Release the retaining tabs on the switch and remove switch from the cluster trim bezel assembly.

Headlamp Switch Replacement

  1. Pry the bezel from the instrument panel extension using a flat-bladed tool.
  2. Remove the electrical connector from the rear fog lamp switch.
  3. Press the tabs on the rear fog lamp switch in order to disengage the tabs from the bezel.
  4. Remove the rear fog lamp switch from the vehicle.
  1. Install the following components to the instrument panel extension: The rear fog lamp switch The bezel
  2. Apply pressure to the rear fog lamp switch in order to engage the tabs on the switch to the bezel.
  3. Install the rear fog lamp switch.
  4. Install the electrical connector to the rear fog lamp switch.
  5. Install the bezel to the lower panel extension.

Scheme 16

Scheme 16: Daytime Running Lamp (DRL) Ambient Light Sensor Replacement
Scheme 16: Daytime Running Lamp (DRL) Ambient Light Sensor Replacement
CalloutComponent Name
1Instrument Panel Upper Trim Pad Refer to Instrument Panel Upper Trim Pad Replacement .
2Daytime Running Lamp Ambient Light Sensor Assembly Procedure Twist and pull down to remove. Disconnect electrical connector.

Daytime Running Lamp (DRL) Ambient Light Sensor Replacement

  1. Gently pry out the lens (2) of the vanity mirror assembly (4) with a suitable flat-bladed tool.
  2. Remove the bulb (3) from the socket.
  1. Install the bulb (3) into the bulb socket.
  2. Install the lens (2) to the vanity mirror assembly (4) by pressing it into place.
  1. Using a flat bladed tool, pry the dome lamp lens open.
  2. Remove the dome lamp lens (2) completely from the dome lamp housing.
  3. Partially remove the dome lamp housing (1) from the headliner.
  4. Disconnect the electrical connector (2) from the dome lamp housing.
  1. Partially install the dome lamp housing (1) to the headliner.
  2. Connect the dome lamp electrical connector (2).
  3. Install the dome lamp lens (2) to the dome lamp housing.
  4. Snap the dome lamp lens (2) into the dome lamp housing.
  1. Using a flat bladed tool, pry the dome lamp lens open.
  2. Remove the dome lamp bulbs (1) from the dome lamp housing.
  1. Install the dome lamp bulbs (1).
  2. Snap the dome lamp lens (2) into the housing.

Scheme 17

Scheme 17: Underhood Lamp Replacement
Scheme 17: Underhood Lamp Replacement
CalloutComponent Name
Preliminary Procedure Open and support the hood. Disconnect the electrical harness connector to the underhood lamp assembly. Release the locking tab securing the underhood lamp to the inner hood panel. Pull the lamp downward in order to remove.
1Underhood Lamp Assembly TIP: Ensure the foam tape strip is attached to the lamp as shown, prior to installation.

Underhood Lamp Replacement

  1. Turn OFF the headlamp switch.
  2. Remove the retaining ring screws from the headlamp. Do not move the adjustment screws.
  3. Remove the retaining ring from the headlamp.
  4. Remove the headlamp from the housing.
  5. Disconnect the electrical connector from the headlamp.
  1. Connect the electrical connector to the headlamp.
  2. Install the headlamp to the housing.
  3. Install the retaining ring to the headlamp.
  4. Install the screws to the retaining ring.

Scheme 18

Scheme 18: Headlamp Replacement (V22)
Scheme 18: Headlamp Replacement (V22)
CalloutComponent Name
Preliminary Procedure Remove the uplevel radiator grille assembly. Refer to Grille Replacement (Base) , Grille Replacement (Uplevel) Aim the headlamps after the headlamp assembly has been replaced. Refer to Headlamp Aiming .
1Headlamp Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 10 N.m (89 lb in)
2Headlamp Radiator Support Nut (Qty: 2)
3Forward Lamp Harness Electrical Connector (Qty: 2)
4Headlamp Assembly WARNING: Refer to Halogen Bulb Warning . TIP: Transfer the headlamp bulb sockets as needed.
CAUTION
Refer to Fastener Caution .
WARNING
Refer to Halogen Bulb Warning .

Headlamp Replacement (V22)

  1. Turn OFF the headlamp switch.
  2. Disconnect the electrical connector from the headlamp bulb.
  3. Rotate the bulb counterclockwise in order to disengage the bulb from the headlamp.
  4. Remove the bulb from the headlamp.
  1. Install the bulb to the headlamp.
  2. Rotate the bulb clockwise in order to engage the bulb in the headlamp.
  3. Connect the electrical connector to the headlamp bulb.

Scheme 19

Scheme 19: Headlamp Capsule Replacement (Minus V22)
Scheme 19: Headlamp Capsule Replacement (Minus V22)
CalloutComponent Name
Preliminary Procedure Remove the base front radiator grille assembly. Refer to Grille Replacement (Base) , Grille Replacement (Uplevel) . Aim the headlamps after the headlamp capsule has been replaced. Refer to Headlamp Aiming .
1Headlamp Adjuster Screw (Qty: 2) TIP: Loosen the screws to assist with the removal of the headlamp capsule from the radiator support.
2Headlamp Capsule TIP: Hold the headlamp capsule when removing the support spring.
3Headlamp Capsule Support Spring
4Headlamp Capsule Electrical Harness Connector
5Radiator Support TIP: Lubricate the perimeter of the headlamp prior to installing the headlamp into the radiator support pocket.

Headlamp Capsule Replacement (Minus V22)

Headlamp Aiming

The screen method is preferred for aiming headlamps. If the headlamp is equipped with aiming pads, headlamp aiming may be performed using the alternate procedure.

Headlamp aiming is done with the vehicle's low beam lamps. The high beam lamps will be correctly aimed if the low beam lamps are aimed properly. If the high beam needs adjustment, follow the screen method using the high beam bulb as the reference for measurements.

Screen Method for Headlamp Aiming (Visual Aim)

IMPORTANTSome state and local laws specify requirements for headlamp aim. All of these laws must be complied with when performing any headlamp aiming operations.

Headlamp aim should be checked

  1. When a new headlamp capsule is installed
  2. If service or repairs to the front end area have (or may have) disturbed the headlamps or their mounting
  1. The area will consist of a level surface large enough to allow for a vehicle and an additional 7.62 m (25 feet) measured from face of lamps to the front of the aiming screen.
  2. The screen will be 1.52 m (5 ft) high x 3.66 m (12 ft) wide with a matte white surface well shaded from extraneous light, and properly adjusted to the floor on which the vehicle stands. Provisions may be made for moving the screen so it can be aligned parallel with the vehicle.
  3. The screen shall be provided with a fixed vertical centerline, two laterally adjustable vertical tapes, and one vertically adjustable horizontal tape.
  4. If a regular commercial aiming screen is not available, the screen may consist of a vertical wall having a clear uninterrupted area approximately 1.83 m (6 ft) high and 3.66 m (12 ft) wide. The surface should be finished with a washable non-gloss white paint.
  5. After the aiming screen has been set up in its permanent location, it is necessary to paint a reference line on the floor directly under the lens of the lamps to indicate the proper location of the headlamps when they are being aimed: Distance between headlamps (1) Center line of screen (2) Adjustable vertical pointer (3) Adjustable horizontal tape (4) Diagram of light screen (5) Vertical center line ahead of right headlamp pointer position (6) 7.62 m (25 ft) (7) Car axis (8) Adjustable vertical pointer Horizontal center line of lamps Vertical center line ahead of left headlamp

Prior to aiming the headlamps, the following steps must be taken

  1. Remove any snow, ice or mud from the vehicle.
  2. The vehicle must have a full tank of gas.
  3. Stop all other work on the vehicle.
  4. If any service has been performed on the vehicle, make sure that all of the components are back in their original place.
  5. The vehicle must be on a level surface.
  6. The vehicle left tires must be aligned with the reference line extending from the screen with the headlamps aligned with the reference line.
  7. Do not load any cargo in the vehicle.
  8. The vehicle must contain one person or 72.56 kg (160 lb) on the driver's seat.
  9. Inflate the tires to the proper pressure.
  10. Simulate the vehicle loads if the intended use of the vehicle is for hauling heavy loads or towing a trailer.
  11. Rock the vehicle in order to stabilize the suspension.
  12. Turn on the headlamps to low beam and observe the left and the top edges of the high intensity zone on the screen. The edges of the high intensity zone should fall within the specifications.

Headlamp Aiming Procedure

  1. Open the hood.
  2. Measure from the floor to the center of the headlamp bulb. (Some headlamps have an aim dot marked on the headlamp lens).
  3. At the screen, measure from the floor and place the horizontal tape at the measured distance.
  4. Measure from the reference line on the floor to the left headlamp bulb centerline.
  5. At the screen, measure from the reference line and place the vertical tape at the measured distance.
  6. Measure from the reference line on the floor to the right headlamp bulb centerline.
  7. At the screen, measure from the reference line and place the vertical tape at the measured distance.
  8. Turn on the low beam headlamps and block the light from projecting onto the screen from the passenger side headlamp.
  9. Adjust the vertical aim of the headlamps to the specifications required by the state and the local authorities, or as shown in step number 8.
  10. Rotate the headlamp adjuster (1) to change the vertical aim of the headlamp.
  11. Repeat the aiming procedure for the passenger side headlamp while blocking the light from projecting onto the screen from the driver side headlamp.
  12. Close the hood.
  13. This illustration represents the visual optics left (VOL) pattern.
  14. This illustration represents the visual optics right (VOR) pattern.
  15. This illustration represents all headlamps, except the VOL and VOR.
  16. This illustration represents the high beam pattern for all headlamps, including VOL and VOR.

Alternate Aiming Procedure

Tool Required

Composite Headlight Aimer Adapter

Instructions for use accompany the tool.

This procedure may only be used on headlamps equipped with aiming pads. Adjustment settings are embossed on the headlamp lens. They are typically located near the aiming pads. In some cases, the adjustment settings are located in other areas of the lens. They will be represented by a number followed by the letter V or the letter H.

  1. Remove any snow, ice or mud from the vehicle.
  2. The vehicle should be fully assembled and all other work stopped while the headlamp aiming is being done.
  3. The vehicle should contain cargo or be loaded to represent normal vehicle use.
  4. Tires should be properly inflated.
  5. Rock the vehicle to stabilize the suspension.
  6. Using, adjust the headlamps to the specifications required by state and local authorities.
  1. Disconnect the electrical connector from the lamp assembly.
  2. Remove the nut retaining the lamp assembly to the bracket.
  3. Remove the lamp assembly from the bumper.
  1. Install the lamp assembly to the bumper.
  2. Install the nut to retain the lamp assembly to the bracket and tighten to 2 N.m (18 in lb).
  3. Install the electrical connector to the lamp assembly.
  1. Remove the screws retaining the lens to the lamp.
  2. Remove the lens from the lamp.
  3. Gently push in on the bulb and turn the bulb 1/4 turn counterclockwise.
  4. Remove the bulb from the socket.
  1. Install the bulb to the socket.
  2. Gently push in on the bulb and turn the bulb 1/4 turn clockwise.
  3. Install the lens to the lamp assembly.
  4. Install the screws to retain the lens to the lamp assembly and tighten to 1.5 N.m (13 lb in).
  1. Remove the screws holding the retaining ring to the headlamp housing assembly.
  2. Remove the retaining ring from the position lamp.
  3. Remove the headlamp capsule (1) from the position lamp.
  4. Remove the bulb (4) and socket from the rubber grommet in the lamp capsule.
  5. Push in on the side of the bulb (4) and turn the bulb 1/4 turn counterclockwise.
  6. Remove the bulb (4) from the socket.
  1. Install the bulb (4) to the socket.
  2. Push in on the bulb (4) and turn 1/4 turn clockwise.
  3. Install the bulb (4) and socket into the rubber grommet in the headlamp capsule (1).
  4. Install the headlamp capsule (1) to the headlamp housing.
  5. Install the retaining ring to the headlamp housing assembly.
  6. Install the screws to the retaining ring to the headlamp housing assembly and tighten to 1.5 N.m (13 lb in).
  1. Push the light assembly (2) towards the front of the vehicle while gently prying the rear edge of the light assembly away from the fender with a small flat-bladed tool in order to remove the light assembly.
  2. Remove the bulb and socket from the light assembly (3) by turning the socket 1/4 turn counterclockwise.
  3. Remove the bulb (1) from the socket.
  1. Install the bulb (1) into the socket.
  2. Turn the socket (3) 1/4 turn clockwise in order to install the socket into the light assembly.
  3. Hook the front tab on the lens into the fender and press the light assembly (2) retaining clip into the fender until fully seated.
  1. Remove the screw (4) that retains the front side marker lamp to the radiator grille.
  2. Lift the side marker lamp (3) up and out in order to disengage the tab.
  3. Disconnect the bulb socket (1) from the side marker lamp.
  4. Remove the bulb (1) from the socket.
  1. Connect the bulb (1) into the socket.
  2. Connect the bulb socket (1) into the side marker lamp.
  3. Install the side marker lamp (3) to the radiator grille (5).
  4. Install the side marker lamp retaining screw (4) and tighten to 1.5 N.m (13 lb in).
  1. Remove the screw (4) that retains the side marker or the reflector to the grille.
  2. Remove the side marker lamp (3) or the reflector (5) from the grille.
  3. Disconnect the bulb socket (2) from the side marker lamp.
  4. Remove the bulb (2) from the socket by turning the bulb in a counter clockwise direction.
  1. Install the bulb (2) into the socket by turning the bulb in a clockwise direction.
  2. Connect the bulb socket (2) into the side marker lamp.
  3. Install the side marker lamp (3) or the reflector (5) to the radiator grille (1).
  4. Install the side marker lamp or reflector retaining screw (4) to the grille and tighten to 1.5 N.m (13 lb in).

Scheme 20

Scheme 20: Parking and Turn Signal Lamp Replacement
Scheme 20: Parking and Turn Signal Lamp Replacement
CalloutComponent Name
Preliminary Procedure Grasp the outboard edge of the turn signal lamp and give a quick pull to release the lamp from the radiator grille assembly.
1Park and Turn Signal Lamp Assembly TIP: Transfer the sockets and bulbs as needed.
2Forward Lamp Harness Electrical Connector (Qty: 2)

Parking and Turn Signal Lamp Replacement

Scheme 21

Scheme 21: High Mount Stop Lamp Replacement
Scheme 21: High Mount Stop Lamp Replacement
CalloutComponent Name
1High Mounted Stop Lamp Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2High Mounted Stop Lamp TIP: Disengage the bulb socket from the lamp assembly.
3High Mounted Stop Lamp Electrical Harness
CAUTION
Refer to Fastener Caution .

High Mount Stop Lamp Replacement

  1. Disconnect the electrical connector.
  2. Using a plastic flat bladed tool, release the double sided tape that retains the light assembly to the vehicle.
  1. Install the light assembly into the vehicle with double sided tape.
  2. Connect the electrical connector.
  1. Disconnect the electrical connector from the lamp assembly.
  2. Remove the nut retaining the lamp assembly to the bracket.
  3. Remove the lamp assembly from the bumper.
  1. Install the lamp assembly to the bumper.
  2. Install the nut to the lamp and tighten to 2 N.m (18 in lb).
  3. Connect the electrical connector to the lamp assembly.

Scheme 22

Scheme 22: Backup Lamp Bulb Replacement
Scheme 22: Backup Lamp Bulb Replacement
CalloutComponent Name
Preliminary Procedures Remove the back body side opening applique. Refer to Back Body Opening Side Applique and Tail Lamp Replacement . Remove the tail lamp assembly. Refer to Tail Lamp Replacement .
1Backup Lamp Socket NOTE: Rotate the socket assembly a quarter turn counterclockwise and remove from the tail lamp assembly.
2Backup Lamp Bulb NOTE: Hold the socket assembly and pull the bulb from the socket.
NOTE
Rotate the socket assembly a quarter turn counterclockwise and remove from the tail lamp assembly.
NOTE
Hold the socket assembly and pull the bulb from the socket.

Backup Lamp Bulb Replacement

Scheme 23

Scheme 23: Rear License Plate Lamp Replacement
Scheme 23: Rear License Plate Lamp Replacement
CalloutComponent Name
1License Lamp Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2License Plate Lamp Housing
3Electrical Connector TIP: Service the bulb as needed.
4Clip Nut (Qty: 2)
CAUTION
Refer to Fastener Caution .

Rear License Plate Lamp Replacement

Scheme 24

Scheme 24: Tail Lamp Replacement
Scheme 24: Tail Lamp Replacement
CalloutComponent Name
Preliminary Procedure Remove the back body side opening applique. Refer to Back Body Opening Side Applique and Tail Lamp Replacement .
1Tail Lamp Nut (Qty: 3) CAUTION: Refer to Fastener Caution . Tighten 5 N.m (44 lb in)
2Tail Lamp Electrical Connector Procedure Pull the lamp assembly rearward. Release the electrical harness rubber grommet. Disconnect the electrical connector from the rearward lamp harness.
3Tail Lamp Assembly TIP: Remove the bulb sockets and service the bulbs as needed.
CAUTION
Refer to Fastener Caution .

Tail Lamp Replacement

Scheme 25

Scheme 25: Stop and Tail Lamp Bulb Replacement
Scheme 25: Stop and Tail Lamp Bulb Replacement
CalloutComponent Name
Preliminary Procedures Remove the back body side opening applique. Refer to Back Body Opening Side Applique and Tail Lamp Replacement . Remove the tail lamp assembly. Refer to Tail Lamp Replacement .
1Stop and Tail Lamp Socket NOTE: Rotate the socket assembly a quarter turn counterclockwise and remove from the tail lamp assembly.
2Stop and Tail Lamp Bulb NOTE: Hold the socket assembly and pull the bulb from the socket.
NOTE
Rotate the socket assembly a quarter turn counterclockwise and remove from the tail lamp assembly.
NOTE
Hold the socket assembly and pull the bulb from the socket.

Stop and Tail Lamp Bulb Replacement

Exterior Lamps

The exterior lighting consist of the following lamps

  1. Headlamps
  2. Daytime running lamps (DRL)
  3. Park lamps
  4. Tail lamps
  5. License lamps
  6. Marker lamps
  7. Turn signal lamps
  8. Stop lamps
  9. Center high mounted stop lamp (CHMSL)
  10. Backup lamps

Low Beam Headlamp Operation

The headlamps may be turned ON in 3 different ways

  1. When the headlamp switch in the HEAD position for normal operations
  2. When the headlamp switch is in the AUTO position, for automatic lamp control (ALC)
  3. When the headlamp switch is placed in the AUTO position, with the windshield wipers ON in daylight conditions, after a 6 second delay

Battery voltage is applied at all times to the coil and switch sides of the LOW BEAM PCB Relay located in the underhood fuse block. With the headlamp switch in the headlamps ON position, ground is applied through the headlamps ON switch signal circuit to the body control module (BCM) signaling the headlamps ON request. In response to this signal, the BCM applies ground through the low beam relay control circuit energizing the LOW BEAM PCB Relay. With the relay energized, battery voltage is applied through the switch side of the relay, the LT and RT LOW BEAM fuses, and the low beam supply voltage circuits illuminating the low beam headlamps.

High Beam Headlamp Operation

Battery voltage is applied at all times to the coil and switch sides of the HIGH BEAM PCB Relay located in the underhood fuse block. When the headlamp dimmer switch is placed in the high beam position, the headlamp dimmer switch signal circuit to the BCM is pulled low signaling the headlamp high beam request. In response to this signal, the BCM applies ground through the high beam relay control circuit energizing the high beam relay. With the relay energized, battery voltage is applied through the switch side of the relay, the LT and RT HIGH BEAM fuses, and the high beam supply voltage circuits illuminating the high beam headlamps. At the same time the BCM sends a serial data message to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator.

Flash to Pass (FTP)

When the headlamp dimmer switch is pulled toward the driver, the flash to pass signal circuit to the BCM is pulled low signaling the flash to pass request. The BCM then turns ON the high beam headlamps as described above until the headlamp dimmer switch is released. If the low beam headlamps were ON during FTP operation they will remain ON.

Daytime Running Lamps (DRL) and Automatic Lamp Control (ALC)

The low beam headlamps are used for DRL operation at a reduced intensity. The DRLs will operate only with the ignition ON, the headlamp switch in the AUTO position, and the gear selector out of the park position. No other exterior lamps such as the parking lamps, tail lamps, etc. will be on when the DRL are being used. The instrument panel will not be illuminated either.

DRL operation is determined by the ambient light sensor and controlled by the body control module (BCM). The ambient light sensor is a light-sensitive transistor used to monitor outside lighting conditions. The BCM provides a 5-volt reference signal to the sensor. The sensor will vary this voltage signal between 0.2 and 4.9 volts depending on outside lighting conditions. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either DRL or ALC operation. When the BCM determines the conditions are met for DRL operation, it applies ground to the DRL relay control circuit energizing the DRL PCB Relay. With the relay energized, battery voltage is applied through the switch side of the relay, the DRL 1 fuse, the DRL 2 fuse, both low beam headlamp fuses, and the low beam supply voltage circuits illuminating the headlamps at a reduced intensity. Any function or condition that turns on the headlamps will cancel DRL operation.

When the BCM detects low light conditions, it will turn OFF the daytime running lamps and turn ON the low beam headlamps as described above in Low Beam Headlamp Operation. The BCM will also turn ON the low beam headlamps in daylight conditions when the windshield wipers are turned ON.

HDLPS Suggested Indicator

If the park lamps are turned ON manually and the ambient light sensor detects a low light condition then the body control module (BCM) will send a message to the instrument panel cluster (IPC) to display the HEADLAMPS SUGGESTED message.

Lights ON Warning

The body control module (BCM) activates the lights ON warning as requested by the headlamp dimmer switch. The lights ON warning sounds when the following occurs

  1. The key is out of the ignition.
  2. The BCM determines that the drivers door is open, signal is low.
  3. The BCM determines that the headlamp switch is in the PARK or HEAD position.

Park, Tail, Marker and License Lamps

The park, tail, and marker lamps are turned ON when the headlamp switch is placed in either the HEAD or PARK lamp positions, or anytime the automatic light control (ALC) turns the headlamps ON. When the headlamp switch is placed in the park lamp or headlamp positions, ground is applied through the switch signal circuit to the BCM indicating the park lamp ON request. In response to this signal, the BCM applies ground through the park lamp relay control circuit energizing the PRK LAMP Relay. With the relay energized, battery voltage is applied through the switch side of the relay, the park lamp fuses, and the supply voltage circuits illuminating the park, license, side marker, and tail lamps.

Turn Signal Lamps

The BCM 3, BCM 5, and BCM 6 fuses located in the underhood fuse block supply battery voltage to the body control module (BCM) for turn signal, hazard lamp, and stop lamp operation. Voltage from the BCM 5 fuse used for the front and rear left turn signals, voltage from the BCM 3 for the right front turn signal, while voltage from the BCM 6 fuse is used for the right rear turn signal. When the turn signal switch is place in either the LEFT or RIGHT position, ground is applied through the turn signal switch signal circuit to the BCM indicating the turn signal request. In response to this signal, the BCM applies a pulsating voltage to the front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. The BCM also sends a message via to the instrument panel cluster (IPC) to cycle the turn signal indicator ON and OFF depending on the position of the turn signal switch.

Hazard Lamps

The hazard flashers may be activated in any power mode. When the hazard lamp switch is placed in the ON position, ground is applied through the hazard switch signal circuit to the body control module (BCM) indicating the hazard lamps ON request. In response to this signal, the BCM applies a pulsating voltage though all front and rear turn signal supply voltage circuits cycling the lamps ON and OFF. The BCM also sends a serial data message to the instrument panel cluster (IPC) to cycle both turn signal indicators ON and OFF.

Stop Lamps

Note. Brake system may use a brake switch, stoplight switch or brakelight switch. System may instead use a Brake Pedal Position Sensor to control these functions.

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the right and left stop lamp control circuits, transmission control module (TCM), engine control module (ECM), center high mounted stop lamp (CHMSL) control circuit, and trailer brake control module if equipped. The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.

The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.

Backup Lamps

When the gear selector is placed in the REVERSE position, the powertrain control module (PCM) sends a serial data message to the BCM indicating the backup lamps ON request. The BCM then applies battery voltage through the backup relay control circuit energizing the BCK/UP LAMP PCB Relay. With the relay energized, battery voltage is applied through the switch side of the relay, the T/LAMP BCK/UP fuse, the AUX/TRLR BCK/UP fuse and the supply voltage circuits illuminating the left and right backup lamps and the backup alarm. The engine may need to be running for the backup lamps to function.

Rear Fog Lamps

The rear fog lamps are located in the rear bumper. The fog lamps will operate only when the ignition in the RUN or CRANK positions. When the rear fog lamp switch is turned ON, ground is applied through the rear fog lamp switch signal circuit to the body control module (BCM) indicating the rear fog lamps ON request. In response to this signal, the BCM applies ground to the rear fog lamp relay control circuit energizing the REAR FOG LP PCB Relay. With the relay energized, battery voltage is applied through the switch side of the relay, the RR FOG LP fuse and the rear fog lamp supply voltage circuit to the left and right rear fog lamps. The BCM sends a serial data message to the instrument panel cluster (IPC) requesting the rear fog lamp indicator be illuminated. The rear fog lamps will deactivate if the headlamps are turned OFF, if the ignition is turned to the OFF position upon a key cycle, or if the driver turns the rear fog lamp switch OFF.

Battery Rundown Protection/Inadvertent Power

The BCM controls the lighting system through circuits that enable the exterior lamp functions of the park lamps, the head lamps, the fog lamps, and the interior lamps. The BCM will open these enabling circuits 10 minutes after the ignition switch is turned OFF with no lamp switch activity. If the ignition switch is turned to any position other than OFF, or if a lamp switch is activated during this time period, the timer will reset for another 10 minutes.

The interior lighting consist of two groups; lamps that may not be manually dimmed (Interior Lamps) and lamps that may be dimmed (Interior Lamps Dimming).

The first group listed below includes lamps that may not be dimmed

  1. Front dome/reading lamps
  2. Middle dome/reading lamps
  3. Rear dome/reading lamps
  4. Sunshade Mirror Lamps
  5. Underhood Lamp

Interior Lamps Features

The interior lamps system features the following functions

  1. An illuminated entry feature that illuminates the courtesy lamps when entering the vehicle or activating the remote keyless entry system.
  2. An illuminated exit feature that illuminates the courtesy lamps when the ignition key has been removed from the ignition.
  3. An inadvertent power feature that supplies voltage to all interior lamps after the ignition is turned OFF. The inadvertent power feature will deactivate all interior lamps after 10 minutes to prevent battery rundown.
  4. A theater dimming feature that will slowly dim the interior lamps from full brightness to OFF.
  5. Individual switches for control of each interior lamp that is not illuminate with the interior lamp switch.

Courtesy Lamps (-YF2/YF7)

When any one of the doors is opened, ground is applied through the door latch door open switch and the door open switch signal circuit to the BCM indicting the door open position. In response to this signal, the BCM then applies battery voltage through the courtesy lamp supply voltage circuits illuminating the courtesy lamps.

Courtesy Lamps (+YF2/YF7)

When any one of the doors is opened, ground is applied through the door latch door open switch and the door open switch signal circuit to the BCM indicting the door open position. In response to this signal, the BCM then applies battery voltage to the courtesy lamp relay control circuit energizing the UPFITTR CTSY LAMPS PCB Relay. With the relay energized. battery voltage is applied through the switch side of the relay and the supply voltage circuits illuminating the courtesy lamps.

Courtesy Lamps Manual Operation

The courtesy lamps can be manually turned ON by the IP dimmer switch. When the dimmer switch is placed in the DOME position, ground is applied through the dimmer switch and the courtesy lamp switch ON signal circuit to the BCM indicating the courtesy lamps ON request. In response to this signal, the BCM then applies battery positive voltage through the courtesy lamp supply voltage circuits illuminating the courtesy lamps listed above. The courtesy lamps ON operation of the dimmer switch will override any BCM operation of the interior lamps already in progress.

Keyless Entry Interior Illumination

When the remote function actuator transmitter is used to unlock the doors, the BCM receives a door-unlock signal. The BCM must have inputs that indicate that the ignition switch is OFF, the courtesy lamp switch is OFF, and all the doors are closed. The BCM will then illuminate the courtesy lamps and will remain illuminated for approximately 25 seconds after the door is closed. If the door locks are activated to the LOCK position, or if the ignition switch is turned to either the RUN or START position, the BCM will turn OFF the courtesy lamps immediately.

Courtesy/Illuminated Exit

The illuminated exit feature will activate the courtesy lamps when the key IN input of the BCM transitions from an active state to an inactive state (removing the ignition key). When the key is removed from the ignition, the key IN input to the BCM becomes inactive. The BCM will illuminate the courtesy lamps for approximately 25 seconds.

Theater Dimming

The theater dimming feature that will slowly dim the interior lamps from full brightness to OFF. The following actions will over ride the theater dimming feature causing the courtesy lamps to deactivate immediately if no other BCM function commands the courtesy lamps ON

  1. A transition from active to inactive of the interior lamps switch, turning OFF the interior lamps switch
  2. A LOCK command from the remote keyless entry system
  3. A last door closed locking function, locking and closing all the doors

Underhood Compartment Lamp

The BCM supplies battery positive voltage through the inadvertent power courtesy lamps circuit to the underhood compartment lamp. When the hood is opened, the underhood compartment lamp switch closes to ground and the lamp illuminates.

Dome/Reading Lamps

The dome/reading lamp is a duel purpose lamp that can be illuminated two different ways. First, the lamp can be turned ON during courtesy lamp operation as described above. Second, the lamps can be turned ON individually for reading lamp operation by the lamp switch. The BCM supplies battery voltage through the inadvertent power courtesy lamp circuit to the dome/reading lamp for reading lamp operation only.

Sunshade Vanity Mirror Lamps

The BCM supplies battery voltage through the inadvertent power courtesy lamps circuit to the left and right vanity mirror lamps. When the vanity mirror cover on the sunshade is opened, the vanity mirror lamp switch is closed to ground and the lamp illuminates.

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.

  1. Headlamp switch
  2. Tow/haul switch
  3. Traction control switch
  4. HVAC control module
  5. Driver window switch
  6. Driver power door lock switch
  7. Auxiliary blower motor switch
  8. Front passenger window switch
  9. Front passenger door lock switch
  10. Front auxiliary HVAC control assembly
  11. Rear auxiliary HVAC control assembly
  12. Steering wheel controls
  13. Inflatable restraint I/P module disable switch
  14. Driver information center (DIC) display switch
  15. Radio

When the ignition switch is turned to the RUN position, the instrument panel cluster (IPC), radio VF display, and the HVAC control assembly turns ON at maximum brightness. When the headlamp switch is in the PARK or HEADLAMP ON position, all incandescent and LED back lighting turn ON at the dimming level indicated by the instrument panel (I/P) dimmer switch. The dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The BCM supplies a voltage reference through the I/P dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the I/P lamps supply voltage circuits and the LED dimming supply circuit to all related interior backlighting lamps illuminating them to the desired level of brightness.

Battery Rundown Protection / Inadvertent Power

The BCM controls the lighting system through circuits that enable the exterior lamp functions of the park lamps, the head lamps, the fog lamps, and the interior lamps. The BCM opens these enabling circuits 10 minutes after the ignition switch is turned OFF with no lamp switch activity. If the ignition switch is turned to any position other than OFF, or if a lamp switch is activated during this time period, the timer resets for another 10 minutes.

Special Tools

Illustration Tool Number/ Description J 25300-E Headlamp Aimer

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• COMPONENT CONNECTOR END VIEWS - INDEX
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Diagnostic Repair Verification
• Body Wiring Harness Junction Block Replacement
• Auxiliary Blower Switch Replacement
• Front Side Door Window Switch Replacement
• Door Lock Switch Replacement
• Tow/Haul Switch Replacement
• Airbag Instrument Panel Module Switch Replacement
• Electronic Traction Control Switch Replacement
• Checking Aftermarket Accessories
• Turn Signal Multifunction Switch Replacement
• Steering Wheel Control Switch Assembly Replacement
• Driver Information Display Switch Replacement
• Battery Disconnect Warning
• Battery Negative Cable Disconnection and Connection
• Fastener Caution
• Instrument Panel Cluster Trim Plate Bezel Replacement
• Grille Replacement (Base)
• Halogen Bulb Warning
• DTC B1395
• Brake Pedal Position Sensor Calibration
• Brake Pedal Position Sensor Replacement
• Stop Lamp Switch Replacement
• Headlamp Aiming