Lighting Systems: Other Chevrolet Silverado 3500 HD

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.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Reference Information

Schematic Reference

Fog Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(ref-317157-S38620028662009060900000) or «Relay Replacement (Within an Electrical Center)»(ref-317157-S17935707512009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Automatic Transmission

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

Manual Transmission

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

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(ref-317157-S38620028662009060900000) or «Relay Replacement (Within an Electrical Center)»(ref-317157-S17935707512009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(ref-317157-S38620028662009060900000) or «Relay Replacement (Within an Electrical Center)»(ref-317157-S17935707512009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

1. If not the specified value, refer to «Brake Warning Indicator Malfunction»(ref-317176-S13790601642009060900000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Refer to the appropriate replacement procedure for the component causing the condition.
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM, driver door lock and side window switch, or passenger door lock and side window switch replacement, setup, and programming

Schematic Reference

Interior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Refer to the appropriate replacement procedure for the component causing the condition.
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM, driver door lock and side window switch, or passenger door lock and side window switch replacement, setup, and programming

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Refer to the appropriate replacement procedure for the component causing the condition.
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Ambient Light Sensor Replacement»(ref-317143-S13229094662009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Refer to the appropriate replacement procedure for the component causing the condition.
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Tail Lamp Bulb Replacement (Chevrolet)»(ref-317143-S39950194172009060900000) or «Tail Lamp Bulb Replacement (GMC)»(ref-317143-S08185330392009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming

Symptoms - Lighting

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) , before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following: «Exterior Lighting Systems Description and Operation»(ref-317143-S06737250512009060900000) «Interior Lighting Systems Description and Operation»(ref-317143-S10491457172009060900000)

Intermittent

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

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Backup Lamp Bulb Replacement (Chevrolet)»(ref-317143-S04270144582009060900000) or «Backup Lamp Bulb Replacement (GMC)»(ref-317143-S15766647552009060900000)
2. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
3. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

1. If the backup lamps do not turn ON and OFF when commanded, refer to «Backup Lamps Malfunction»(ref-317143-S26923462662009072300000) .
2. If the backup lamps turn ON and OFF when commanded, refer to «Backup Lamp Switch Malfunction»(ref-317143-S24603383332009072300000) .

Backup Lamp Switch Malfunction

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

Backup Lamps Malfunction

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Backup Lamp Bulb Replacement (Chevrolet)»(ref-317143-S04270144582009060900000) or «Backup Lamp Bulb Replacement (GMC)»(ref-317143-S15766647552009060900000)
2. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
3. «Backup Lamp Switch Replacement»(ref-317138-S10790146912009060900000)
4. «Control Module References»(ref-317173-S10180079792009060900000) for BCM or ECM replacement, setup, and programming

Schematic Reference

Interior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, command the Courtesy Lamps output control ON and OFF with the scan tool. The interior courtesy lamps should turn ON and OFF. If one or more of the courtesy lamps are always ON or always OFF refer to «Courtesy Lamp Malfunction»(ref-317143-S30138662592009072300000) .
2. Observe the scan tool Driver Door Switch, Driver Door Open Sw. parameter while opening and closing the driver door. The reading should change between Active and Inactive. If the Driver Door Open Sw. parameter does not change between Active and Inactive, refer to «Door Open Switch Malfunction - Front w/AN3»(ref-317143-S20832236032009072300000) .
3. Observe the scan tool Passenger Door Switch, Passenger Door Open Sw. parameter while opening and closing the front passenger door. The reading should change between Active and Inactive. If the Passenger Door Open Sw. parameter does not change between Active and Inactive, refer to «Door Open Switch Malfunction - Front w/AN3»(ref-317143-S20832236032009072300000) .
4. Observe the scan tool BCM Ctsy. Lamp Actv. Reason parameter while opening and closing each rear doors one at a time. The reading should change between Door Open and Door Closed If the Ctsy. Lamp Actv. Reason parameter does not change between Door Open and Door Closed, refer to «Door Open Switch Malfunction - Rear»(ref-317143-S04098260132009072300000) .
5. Ignition ON and all doors closed, observe the scan tool BCM Ctsy. Lamp Actv. Reason parameter while turning the dome lamp switch ON and OFF. The reading should change between Off and Manual. If the Ctsy. Lamp Actv. Reason parameter does not change between Off and Manual, refer to «Dome/Interior Lamp Switch Malfunction»(ref-317143-S37721388402009072300000) .
6. Ignition ON and all doors closed, observe the scan tool BCM Ctsy. Lamp Actv. Reason parameter while turning the interior lamp defeat switch ON and OFF. The reading should change between Off and Manual Defeat. If the Ctsy. Lamp Actv. Reason parameter does not change between Off and Manual, refer to «Dome/Interior Lamp Switch Malfunction»(ref-317143-S37721388402009072300000) .
7. Ignition ON, command the Puddle/Courtesy Lamp ON and OFF with a scan tool. Verify the exterior illumination lamps turn ON and OFF. If the exterior illumination lamps do not change between ON and OFF, refer to «Exterior Lamps Circuit Test»(ref-317143-S15001030212009072300000) .
8. Ignition ON, turn the reading lamps ON and OFF. The reading lamps should turn ON and OFF. If the reading lamps do not change between ON and OFF, refer to «Reading Lamps Malfunction»(ref-317143-S11871034702009072300000) test.
9. Ignition On, fold down the sun visors and verify the vanity lamps illuminate. If the vanity lamps do not change between ON and OFF, refer to «Vanity Mirrors Malfunction»(ref-317143-S11622525952009072300000) .

Courtesy Lamp Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate lamp.
2. Test for less than 5 ohms between the ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal and the ground circuit terminal.
4. Ignition ON, command the Courtesy Lamps output control ON and OFF with the scan tool. The test lamp should turn ON and OFF. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the appropriate bulb.

Door Open Switch Malfunction - Front w/AN3

1. Ignition OFF, disconnect the harness connector at the inoperative door latch assembly.
2. Test for less than 10.0 ohms between the appropriate ground circuit terminal listed below and ground. Driver door latch ground circuit terminal 5 Passenger door latch ground circuit terminal 3 If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Door Open Switch parameter is INACTIVE. If the scan tool displays ACTIVE, test the appropriate signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the appropriate door control module. Driver door open switch signal circuit terminal 7 Passenger door open switch signal circuit terminal 2
4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the scan tool Door Open Switch parameter is ACTIVE. Driver door open switch signal circuit terminal 7 Passenger door open switch signal circuit terminal 2 If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the appropriate door control module.
5. If all circuits test normal, replace the inoperative door latch assembly.

Door Open Switch Malfunction - Front w/o AN3

1. Ignition OFF, disconnect the harness connector at the inoperative door latch assembly.
2. Test for less than 10.0 ohms between the appropriate ground circuit terminal listed below and ground. w/ power door locks terminal 8 w/o power door locks terminal 6 If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Door Open Switch parameter is INACTIVE. If the scan tool displays ACTIVE, test the appropriate signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the BCM. w/ power door locks terminal 7 w/o power door locks terminal 5
4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the scan tool Door Open Switch parameter is ACTIVE. w/ power door locks terminal 7 to terminal 8 w/o power door locks terminal 6 to terminal 5 If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, replace the inoperative door latch assembly.

Door Open Switch Malfunction - Rear

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

Dome/Interior Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for less than 5 ohms between the ground circuit terminal 8 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Ctsy. Lamp Actv. Reason parameter is Off. If the scan tool parameter is Manual or Manual Defeat, test the appropriate signal circuit terminals for a short to ground. If the circuit tests normal, replace the BCM. Manual terminal 12 Manual Defeat terminal 9
4. Install a 3A fused jumper wire between the signal circuit terminal 12 and the ground circuit terminal 8. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Manual. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. Install a 3A fused jumper wire between the signal circuit terminal 9 and the ground circuit terminal 8. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Manual Defeat. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
6. If all circuits test normal, test or replace the headlamp switch.

Outside Rearview Mirror Illumination Malfunction

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

Reading Lamps Malfunction

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

Vanity Mirrors Malfunction

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Dome Lamp Replacement»(ref-317143-S08499913642009060900000)
2. «Front Side Door Lock Replacement»(ref-317153-S22010634822009060900000)
3. «Rear Door Lock Replacement (Crew Cab)»(ref-317153-S33919070212009060900000) or «Rear Door Lock Replacement (Extended Cab Upper)»(ref-317153-S35682647142009060900000) or «Rear Door Lock Replacement (Extended Cab Lower)»(ref-317153-S33114384132009060900000)
4. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
5. «Control Module References»(ref-317173-S10180079792009060900000) for BCM, driver door switch, or passenger door switch replacement, programming, and setup

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, with a scan tool command the Low Beams ON and OFF. The low beam headlamps should turn ON and OFF when changing between the commanded states. If the low beam headlamps do not turn ON and OFF when commanded, refer to «Headlamps Malfunction»(ref-317143-S20224757782009060900000) .
2. Ignition ON, park brake released, verify with a scan tool the Park Brake Switch parameter displays Released. If not the specified value, refer to «Brake Warning Indicator Malfunction»(ref-317176-S13790601642009060900000) .
3. Ignition ON, with a scan tool command the DRL ON and OFF. The low beam headlamps should turn ON and OFF when changing between the commanded states. If the low beam headlamps do not turn ON and OFF when commanded, refer to «Daytime Running Lamps Malfunction»(ref-317143-S31996542652009072300000) . If the low beam headlamps turn ON and OFF when commanded, refer to «Ambient Light Sensor Malfunction»(ref-317143-S32191190702009072300000) .

Daytime Running Lamps Malfunction

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

Ambient Light Sensor Malfunction

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Ambient Light Sensor Replacement»(ref-317143-S13229094662009060900000)
2. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
3. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Fog Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

1. If the reading does not change between the commanded states, refer to «Fog Lamp Switch Malfunction»(ref-317143-S11017387032009072300000) .

Fog Lamp Switch Malfunction

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

Fog Lamps Malfunction

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fog Lamp Switch Replacement (with RPO SLT)»(ref-317143-S29226475182009060900000) or «Fog Lamp Switch Replacement (without RPO SLT)»(ref-317143-S04903481642009060900000)
2. «Front Fog Lamp Replacement (Chevrolet)»(ref-317143-S01799557502009060900000) or «Front Fog Lamp Replacement (GMC)»(ref-317143-S37072367642009060900000)
3. «Relay Replacement (Attached to Wire Harness)»(ref-317157-S38620028662009060900000) or «Relay Replacement (Within an Electrical Center)»(ref-317157-S17935707512009060900000)
4. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, setup, and programming

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

Hazard Lamps Malfunction

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

Hazard Lamp Indicators Malfunction

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

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Turn Signal Multifunction Switch Replacement»(ref-317148-S17605454052009060900000)
2. «Control Module References»(ref-317173-S10180079792009060900000) for BCM or IPC replacement, setup, and programming

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool Headlamp Switch parameter while turning the headlamp switch ON and OFF. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Switch Malfunction»(ref-317143-S30385777152009072300000) .
2. Observe the scan tool Flash to Pass Switch parameter while applying and releasing the flash to pass switch. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Dimmer Switch Malfunction»(ref-317143-S07179509112009072300000) .
3. Observe the scan tool High Beam Select Switch parameter while applying and releasing the high beam select switch. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Dimmer Switch Malfunction»(ref-317143-S07179509112009072300000) .
4. Observe the scan tool Auto Hdlp. Disable Sw. parameter while applying and releasing the automatic lamp control disable switch. The reading should toggle between Active and Inactive. If the reading does not change between the commanded states, refer to «Headlamp Switch Malfunction»(ref-317143-S30385777152009072300000) .
5. Command the Low Beams ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when commanded. If the low beam headlamps do not turn ON and OFF when commanded, refer to «Headlamps Malfunction - Low Beam»(ref-317143-S23518441992009072300000) .
6. Command the High Beams ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when commanded. If the high beam headlamps do not turn ON and OFF when commanded, refer to «Headlamps Malfunction - High Beam»(ref-317143-S09921063372009072300000) .

Headlamp Switch Malfunction

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

Headlamp Dimmer Switch Malfunction

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

Headlamps Malfunction - Low Beam

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

Headlamps Malfunction - High Beam

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

High Beam Indicator Malfunction

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

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
2. «Headlamp Replacement (Chevrolet)»(ref-317143-S01085033082009060900000) or «Headlamp Replacement (GMC HD)»(ref-317143-S20240188832009060900000) or «Headlamp Replacement (HD Diesel)»(ref-317143-S02599262252009060900000)
3. «Headlamp Bulb Replacement (Chevrolet)»(ref-317143-S12425491522009060900000) or «Headlamp Bulb Replacement (GMC)»(ref-317143-S32596195992009060900000)
4. «Underhood Electrical Center or Junction Block Replacement»(ref-317157-S09014671232009060900000)
5. «Turn Signal Multifunction Switch Replacement»(ref-317148-S17605454052009060900000)
6. «Control Module References»(ref-317173-S10180079792009060900000) for BCM or IPC replacement, setup, and programming

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the driver door switch while commanding the Driver Door Switch Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or remains always ON, replace the driver door lock and side window switch.
2. Ignition ON, observe the driver memory/heated seat switch while commanding the Driver Door Switch Non-Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or remains always ON, refer to «Interior Backlighting Malfunction - Incandescent»(ref-317143-S20257357112009072300000) .
3. Ignition ON, observe the passenger door switch while commanding the Passenger Door Switch Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or always remains ON, replace the passenger door lock and side window switch.
4. Ignition ON, observe the passenger heated seat switch while commanding the Passenger Door Switch Non-Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states. If the backlighting does not turn On and OFF or remains always ON, refer to «Interior Backlighting Malfunction - Incandescent»(ref-317143-S20257357112009072300000) .
5. Ignition ON, observe the scan tool BCM Dimming Control Signal parameter while operating the dimmer switch from high to low. The reading should change from a high percent to a low percent as the switch is rotated. If the reading does not change, refer to «LED Dimming Circuit Test»(ref-317143-S31439534902009072300000) .

1. If the scan tool dimmer control operates normal, refer to the «Interior Backlighting Malfunction - Incandescent»(ref-317143-S20257357112009072300000) or the «LED Dimming Circuit Test»(ref-317143-S31439534902009072300000) .

Interior Backlighting Malfunction - Incandescent

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

Dimmer Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
2. Verify that a test lamp illuminates between the ground circuit terminal 8 and B+. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Dimming Control Signal parameter is less than 0.1 volts. If greater than the specified range, test the signal circuit terminal 13 for a short to voltage. If the circuit tests normal, replace the BCM.
4. Ignition ON, test for B+ between the I/P dimming voltage reference circuit terminal 15 and ground. If less than the specified value, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
5. Install a 3A fused jumper wire between the signal circuit terminal 13 and the voltage reference circuit terminal 15. Verify the scan tool BCM Dimming Control Signal parameter is greater than 2.6 volts. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
6. If all circuits test normal, test or replace the headlamp and panel dimmer switch.

Interior Backlighting Malfunction

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Front Seat Heater Switch Replacement»(ref-317177-S19198672082009060900000)
2. «Steering Wheel Control Switch Assembly Replacement»(ref-317178-S33743399072009060900000)
3. «Driver Information Display Switch Replacement (with RPO SLT)»(ref-317147-S15011917632009060900000) or «Driver Information Display Switch Replacement (without RPO SLT)»(ref-317147-S27111592812009060900000)
4. «Accessory Switch Replacement (with RPO SLT)»(ref-317147-S31969040112009060900000) or «Accessory Switch Replacement (without RPO SLT)»(ref-317147-S42041820052009060900000)
5. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
6. «Control Module References»(ref-317173-S10180079792009060900000) for BCM, door lock and side window switch, IPC, radio, HVAC control module, and rear seat audio controller replacement, programming, and setup.

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

1. If the reading does not change, refer to «Dimmer Switch Circuit Test»(ref-317143-S24404450262009072300000) .

1. If the scan tool dimmer control operates normal, refer to the «Interior Backlighting Malfunction - LED»(ref-317143-S31520596162009072300000) .

Interior Backlighting Malfunction - LED

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Front Seat Heater Switch Replacement»(ref-317177-S19198672082009060900000)
2. «Steering Wheel Control Switch Assembly Replacement»(ref-317178-S33743399072009060900000)
3. «Driver Information Display Switch Replacement (with RPO SLT)»(ref-317147-S15011917632009060900000) or «Driver Information Display Switch Replacement (without RPO SLT)»(ref-317147-S27111592812009060900000)
4. «Accessory Switch Replacement (with RPO SLT)»(ref-317147-S31969040112009060900000) or «Accessory Switch Replacement (without RPO SLT)»(ref-317147-S42041820052009060900000)
5. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
6. «Control Module References»(ref-317173-S10180079792009060900000) for BCM, IPC, radio, and HVAC control module replacement, programming, and setup.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool parklamp switch parameter while cycling the headlamp switch between the park and off positions. The parameter should cycle between active and inactive. If the parameter does not cycle between the specified values, refer to «Park Lamp Switch Circuit Test»(ref-317143-S41574872572009072300000) .
2. Connect a test lamp between the relay side of a park lamp fuse and ground.
3. Command the parking lamps on and off with a scan tool. Verify that the test lamp turns on and off while switching between the commanded states. If the test lamp does not turn on and off while changing between the commanded states, refer to the «Park Lamp Relay Circuit Test»(ref-317143-S28775310822009072300000) .
4. If any of the park, marker, license, or tail lamps do not turn on and off, refer to «Exterior Lamps Circuit Test»(ref-317143-S15001030212009072300000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Parking and Turn Signal Lamp Bulb Replacement (Chevrolet)»(ref-317143-S34351233712009060900000) or «Parking and Turn Signal Lamp Bulb Replacement (GMC)»(ref-317143-S16870719932009060900000)
2. «Rear License Plate Lamp Replacement (Silverado)»(ref-317143-S11262639822009060900000) or «Rear License Plate Lamp Replacement (VF7)»(ref-317143-S12762035412009060900000)
3. «Tail Lamp Bulb Replacement (Chevrolet)»(ref-317143-S39950194172009060900000) or «Tail Lamp Bulb Replacement (GMC)»(ref-317143-S08185330392009060900000)
4. «Headlamp Switch Replacement (with RPO SLT)»(ref-317143-S36368614332009060900000) or «Headlamp Switch Replacement (without RPO SLT)»(ref-317143-S09203669152009060900000)
5. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, programming, and setup.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool BCM Stop Lamp Switch Status parameter while pressing and releasing the brake pedal. The reading should change between 1 count and approximately 1023 counts. If not the specified value, refer to the «Stop Lamp Switch Circuit Test»(ref-317143-S11880099262009072300000) .
2. Ignition ON, observe the scan tool TCM Brake Switch parameter while pressing and releasing the brake pedal. The reading should change between Pressed and Released. If not the specified value, refer to the «Stop Lamp Switch Circuit Test»(ref-317143-S11880099262009072300000) .
3. Ignition ON, observe the left, and right stop lamps while pressing and releasing the brake pedal. The stop lamps should turn on and off. If the left and or right stop lamps are always on or inoperative, refer to the «Stop Lamp Switch Circuit Test»(ref-317143-S11880099262009072300000) .
4. Connect a test lamp between the relay side of the CHMSL fuse and ground.
5. Verify that the test lamp turns on and off while pressing and releasing the brake pedal. If the test lamp does not turn on and off while changing between the commanded states, refer to the «CHMSL Relay Control Circuit Test»(ref-317143-S40185039202009072300000) .
6. If the center high mount stop lamp is always on or inoperative refer to the «CHMSL Relay Control Circuit Test»(ref-317143-S40185039202009072300000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Stop Lamp Switch Replacement (With Adjustable Pedals)»(ref-317143-S03856524842009060900000) or «Stop Lamp Switch Replacement (Without Adjustable Pedals)»(ref-317143-S41866902062009060900000)
2. «High Mount Stop Lamp Replacement (Extended and Crew Cab)»(ref-317143-S14167381002009060900000) or «High Mount Stop Lamp Replacement (Regular Cab)»(ref-317143-S05691526572009060900000)
3. «Tail Lamp Bulb Replacement (Chevrolet)»(ref-317143-S39950194172009060900000) or «Tail Lamp Bulb Replacement (GMC)»(ref-317143-S08185330392009060900000)
4. «Control Module References»(ref-317173-S10180079792009060900000) for BCM replacement, programming, and setup.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-317172-S12100958872009060900000)
2. «Connector Repairs»(ref-317172-S41839496312009060900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-317172-S08096213032009060900000)
4. «Wiring Repairs»(ref-317172-S40815672902009060900000)

Scan Tool Reference

Control Module References for scan tool information

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

1. If the parameters do not change between the commanded states, refer to «Turn Signal Switch Malfunction»(ref-317143-S26095746562009072300000) .
2. If the parameters change between the commanded states, refer to «Turn Signal Switch Malfunction»(ref-317143-S26095746562009072300000) .

Turn Signal Switch Malfunction

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

Turn Signal Lamps Malfunction

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

Turn Signal Indicators Malfunction

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

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Parking and Turn Signal Lamp Bulb Replacement (Chevrolet)»(ref-317143-S34351233712009060900000) or «Parking and Turn Signal Lamp Bulb Replacement (GMC)»(ref-317143-S16870719932009060900000)
2. «Tail Lamp Bulb Replacement (Chevrolet)»(ref-317143-S39950194172009060900000) or «Tail Lamp Bulb Replacement (GMC)»(ref-317143-S08185330392009060900000)
3. «Turn Signal Multifunction Switch Replacement»(ref-317148-S17605454052009060900000)
4. «Control Module References»(ref-317173-S10180079792009060900000) for BCM or IPC replacement, setup, and programming

Headlamp Aiming (Chevrolet/GMC)

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

Screen Method for Headlamp Aiming (Visual Aim)

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

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

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

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

Headlamp Aiming Procedure

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

Scheme 37

Scheme 38

Scheme 39

Scheme 40

Fog Lamp Aiming

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

Preparation Procedure

1. Completely assemble all of the components on the vehicle.
2. Park the vehicle on a level surface.
3. Stop all unnecessary operations or work on the vehicle that affect the vehicle trim.
4. Close the doors and ensure that the vehicle has no load other than the driver.
5. Stabilize the suspension by rocking the vehicle sideways.
6. Ensure that the fuel level is 1/2 full.
7. Ensure that the tires are inflated to the proper pressure.
8. Ensure that the driver or a similar weight, approximately 75 kg (165 lb), is in the vehicle driver seat.

Aiming Procedure

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

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Scheme 51

Scheme 52

Scheme 53

Exterior Lamps

The exterior lighting system consists of the following lamps

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

Headlamps

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

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

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

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

High Beams

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

Low Beams

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

Daytime Running Lamps (DRL)

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

Fog Lamps

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

Park, Tail and Marker Lamps

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

Exterior Courtesy Lamps

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

Turn Signal/Hazard Lamps

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

Stop Lamps

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

Backup Lamps

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

Cargo Lamps

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

Clearance Lamps

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

Interior Lamps

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

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

Courtesy/Illuminated Entry Lamps

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

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

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

Keyless Entry Interior Illumination

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

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

Vanity Lamps

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

Reading Lamps

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

Battery Rundown Protection/Inadvertent Power

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

Interior Lamps Dimming

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

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

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

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

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

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

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

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

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

The modules controlling the above indicators are as follows

1. Transfer case shift control module
2. BCM