Lighting Systems: Diagnosis Chevrolet Silverado 2500 HD

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Lighting

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

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

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

Scan Tool Output Controls

Body Control Module (BCM)

Driver Door Switch

Export Body Control Module (XBCM)

Instrument Panel Cluster (IPC)

Passenger Door Switch

Scan Tool Data List

Body Control Module (BCM)

Driver Door Switch

Export Body Control Module (XBCM)

Passenger Door Switch

Scan Tool Data Definitions

The Scan Tool Data Definitions contains a brief description of all Lighting System related parameters available on the scan tool.

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

Diagnostic Fault Information

DTC B257A

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The BCM receives a mismatched signal between the headlamp switch headlamps OFF signal circuit, the headlamps switch headlamps ON signal circuit, and the headlamp switch parklamps signal circuit.

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

Circuit/System Testing

DTC B257A

1. Ignition OFF, disconnect the BCM connector C2 and start with the headlamp switch in the AUTO position. Use the chart above to determine when and where a ground signal should be present. Test each connector circuit listed in the chart for the proper signal.
2. If voltage is present on any circuit, test that circuit for a short to voltage. If the circuit/connections test normal, replace the headlamp and panel dimmer switch.
3. If no ground signals are present, test the headlamp switch ground circuit for an open. If the circuit/connections test normal, replace the headlamp and panel dimmer switch.
4. If all signal functions of the headlamp and panel dimmer switch circuits test normal, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B1395

The ignition is ON.

1. Clear the DTC.
2. Use a scan tool to monitor the Dimming Control Reference Signal data parameter in the BCM data list. If less than 0.33 volt, test the I/P dimming voltage reference circuit for a short to ground or an open/high resistance and test the stop lamp signal circuit for a short to ground. If the circuit/connections test normal, replace the BCM. If greater than 4.97 volts, test the I/P dimming voltage reference circuit for a short to voltage. If the circuit/connections test normal, replace the BCM.
3. If the voltage is correct and all circuits/connections test normal, replace the headlamp switch.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2530

1. The ignition is ON.
2. Park lamps must be ON and the fog lamps must be commanded ON.

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

The front fog lamps do not illuminate.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, remove the fog lamp relay in the underhood fuse block.
2. Ignition ON, test for voltage at the relay control circuit terminal of the underhood fuse block. If voltage is present, test the control circuit for a short to voltage. If all circuits/connections test normal, replace the fog lamp relay.

1. If voltage is not present, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2545

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

The BCM detects a short to ground on the backup lamp relay control circuit when the backup lamps are being commanded ON.

The backup lamps do not illuminate.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, disconnect the underhood fuse block connector C 5, inside rearview mirror, and rearview camera module (if equipped) that are in the circuit.
2. Ignition OFF, disconnect the BCM harness connector C2 and test for a ground signal at the connector terminal 22. If the circuit exhibits a ground signal, repair the short to ground in the control circuit.
3. Reconnect the inside rearview mirror and test the BCM harness connector C2, terminal 22 again for ground. If the circuit now exhibits a ground signal of 20 ohms or less, replace the inside rearview mirror.
4. Reconnect the underhood fuse block connector and test the BCM harness connector C2, terminal 22 again for ground. If the circuit now exhibits a ground signal of 20 ohms or less, replace the underhood fuse block.
5. If equipped, reconnect the rearview camera module and test the BCM harness connector C2, terminal 22 again for ground. If the circuit now exhibits a ground signal of 20 ohms or less, replace the rearview camera module.

1. If the circuit does not exhibit a ground, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2555

1. Battery voltage must be between 9-16 volts.
2. A message is sent from the BCM over the GM LAN serial data circuit to the driver door and passenger door switches to active the door courtesy lamps.

1. Disconnect the driver or passenger door harness connector C2 as applicable.
2. Connect a test lamp between the courtesy lamp control circuit terminal 10 at the door harness connector and ground. If the test lamp illuminates, locate and repair a short to voltage in the courtesy lamp control circuit. If the test lamp does not illuminate, locate and repair a short to ground in the courtesy lamp control circuit.
3. If circuits test OK, replace the driver or passenger door switch as applicable.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2575

Conditions for Running the DTCs

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

Condition for Setting the DTC

The headlamp low beam relay control circuit is shorted to voltage.

The BCM turns off the headlamp low beam relay control for the remainder of the ignition cycle.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, remove the low beam relay in the underhood fuse block.
2. Ignition ON, test for voltage at the relay control circuit terminal of the underhood fuse block. If voltage is present, test the control circuit for a short to voltage. If all circuits/connections test normal, replace the low beam relay.

1. If voltage is not present, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2580

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

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

The high beam headlamps are inoperative.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, disconnect the BCM connector C4.
2. Ignition ON, test for voltage at the BCM harness connector terminal 16. If voltage is present, test the control circuit for a short to voltage. If all circuits/connections test normal, replace the underhood fuse block.

1. If voltage is not present, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2585

1. The Ignition is ON.
2. The park lamps must be commanded ON by the BCM.

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

All park, license, and tail lamps are inoperative.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, remove the park lamp relay from the underhood fuse block.
2. Ignition ON, test for voltage at the relay control circuit terminal of the underhood fuse block. If voltage is present, test the control circuit for a short to voltage. If all circuits/connections test normal, replace the relay.

1. If voltage is not present, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2600

1. The headlamp switch is OFF.
2. The park brake is unapplied.
3. The engine is running.

The DRL relay control circuit is shorted to voltage.

The BCM turns off the DRL relay control for the remainder of the ignition cycle.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, disconnect the BCM connector C4.
2. Ignition ON, test for voltage at the BCM harness connector terminal 23. If voltage is present, test the control circuit for a short to voltage. If all circuits/connections test normal, replace the underhood fuse block.

1. If voltage is not present, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2610

The ignition is ON.

The BCM, driver door switch, and passenger door switch detects a short to voltage, short to ground, or an open on the LED dimming supply circuit.

The BCM, driver door switch, and passenger door switch will cease attempts to dim or illuminate the LED lamps.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Park lamps OFF, disconnect all of the LED dimming supply circuit lamp components on the circuit.
2. Park lamps ON, verify that DTC B2610 00, B2610 01, and DTC B2610 02 does not reset. If the DTC resets, test for a short to voltage, short to ground, or an open in the LED dimming supply circuit. If the circuit/connections test normal, replace the BCM, driver door switch, and passenger door switch as applicable.
3. Reconnect each component one at a time and test for DTC B2610 00, B2610 01 and DTC B2610 02. If the DTC resets, replace that particular component.

1. If the DTC does not reset, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2615

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

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

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

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, disconnect all the courtesy lamps voltage supply circuit lamp components on the circuit.
2. Verify that DTC B2615 00, B2615 01, DTC B2615 02, and/or DTC B2615 04 does not reset. If the DTC resets, test for a short to voltage, short to ground, or an open in the courtesy lamps supply voltage circuit. If the circuit/connections test normal, replace the BCM, driver door switch, and passenger door switch as applicable.
3. Reconnect each component one at a time and test for DTC B2615 00, B2615 01, DTC B2615 02, and/or DTC B2615 04. If the DTC resets, replace that particular component.

1. If the DTC does not reset, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2625

The ignition is ON.

The BCM receives a ground signal on the LED indicator dimming supply circuit.

The BCM cease attempt to dim or illuminate the LED indicator lamps.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, park lamps OFF, disconnect all the LED indicator dimming supply circuit lamp components on the circuit. Verify DTC B2625 does not set. If the DTC resets, test for a short to voltage, short to ground, or an open in the LED indicator dimming supply voltage circuit. If the circuit/connections test normal, replace the BCM, driver door switch, and passenger door switch as applicable.
2. Reconnect each component one at a time and test for the DTC B2625. If the DTC resets, replace that particular component.

1. If the DTC does not reset, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2645

Battery voltage must be between 9-16 volts.

1. Ignition OFF, disconnect the ambient light sensor.
2. Ignition ON, monitor the Ambient Light Sensor parameter in the BCM data list with a scan tool. If the scan tool parameter is less than 0.2 volt, test for a short to ground in the ambient light sensor signal circuit. If a short to ground is not found, replace the BCM. If the scan tool parameter is greater than 4.9 volts, test for an open or short to voltage in the ambient light sensor signal circuit or an open in the ambient light sensor ground circuit. If any of those conditions are not found, replace the ambient light sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B2652

The ignition is ON.

The BCM receives an open, voltage, or ground signal on the I/P lamp dimming control circuit.

The I/P lamps are not illuminated.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, park lamps OFF, disconnect all of the lamp components on the I/P lamp dimming control circuit. Verify DTC B2652 00 does not set. If the DTC resets, test for a short to voltage, short to ground, or an open in the I/P lamp dimming control circuit and for an open in the dimmer switch 5-volt reference circuit. If the circuit/connections test normal, replace the BCM.
2. Reconnect each component one at a time and test for the DTC B2652 00. If the DTC resets, replace that particular component.

1. If the DTC does not reset, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B3445

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

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

The stop lamps do not illuminate.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Disconnect the stop lamps and test the individual stop lamp assemblies for internal shorts between all terminals. If a short between terminals is found, replace the stop lamp socket or circuit board as applicable.
2. Test the stop lamp supply voltage circuit for a short to ground. If all circuits/connections test normal, replace the BCM.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B3600

The ignition is ON.

1. Ignition ON and clear the DTC. Use the scan tool Incandescent Dimming output control to adjust the dimming level of the I/P lamps from low to high. If the lamps cannot be controlled with the scan tool, replace the BCM.
2. Monitor the Dimming Control Signal voltage parameter in the scan tool BCM data list while adjusting the dimmer switch from high to low.
3. If the voltage is above 4.97 volts, test for a short to voltage in the I/P lamp dimmer switch signal circuit. If the circuit/connections test normal, replace the headlamp and panel dimmer switch.
4. If the voltage drops below 0.10 volt, test for a short to ground, open, or high resistance in the I/P lamp dimmer switch signal circuit. If the circuit/connections test normal, replace the headlamp and panel dimmer switch.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

DTC B3884

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

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

The CHMSL does not illuminate.

1. The conditions for setting the DTC are no longer present.
2. A history DTC clears after 100 malfunction-free ignition cycles.
3. The BCM receives the clear code command from the scan tool.

1. Ignition OFF, disconnect the X5 harness connector at the underhood fuse block.
2. Connect a test lamp between the CHMSL relay control circuit terminal K6 and ground at the harness connector.
3. Apply the brake pedal ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
4. If all circuits test normal, test or replace the underhood fuse block.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Lighting System. Refer to «Checking Aftermarket Accessories»(ref-278019-S10639375482008012100000) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

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

1. «Backup Lamps Always On»(ref-277990-S16095512622008012100000)
2. «Backup Lamps Inoperative»(ref-277990-S26636462752008012100000)
3. «High Mount Stop Lamp Malfunction»(ref-277990-S27637532672008012100000)
4. «Clearance Lamps Inoperative»(ref-277990-S29839011232008012100000)
5. «Courtesy Lamps Always On»(ref-277990-S21198083602008012100000)
6. «Courtesy Lamps Inoperative»(ref-277990-S11662816472008012100000)
7. «Daytime Running Lamps (DRL) Always On»(ref-277990-S36152861942008012100000)
8. «Daytime Running Lamps (DRL) Defeat Inoperative»(ref-277990-S33616849032008012100000)
9. «Daytime Running Lamps (DRL) Inoperative (Z88)»(ref-277990-S22202995082008012100000) or «Daytime Running Lamps (DRL) Inoperative (X88 and Z75)»(ref-277990-S29432731702008012100000)
10. «Exterior Courtesy Lamp(s) Always On»(ref-277990-S07554815922008012100000)
11. «Exterior Courtesy Lamp(s) Inoperative»(ref-277990-S33024619092008012100000)
12. «Fog Lamp Indicator Inoperative»(ref-277990-S28840050542008012100000)
13. «Fog Lamps Always On»(ref-277990-S07734649752008012100000)
14. «Fog Lamps Inoperative»(ref-277990-S12885196812008012100000)
15. «Hazard Lamps Always On»(ref-277990-S22895282812008012100000)
16. «Hazard Lamps Inoperative»(ref-277990-S22551495312008012100000)
17. «Headlamp Low or High Beams Always On»(ref-277990-S14038408202008012100000)
18. «Headlamps Inoperative - High Beams»(ref-277990-S25561072982008012100000)
19. «Headlamps Inoperative - Low Beams (Standard)»(ref-277990-S28240309232008012100000)
20. «Low and High Beams Headlamps Inoperative»(ref-277990-S13803224982008012100000)
21. «Headlamps Flash to Pass Inoperative»(ref-277990-S29723033782008012100000)
22. «High Beam Indicator Always On»(ref-277990-S30859024842008012100000)
23. «High Beam Indicator Inoperative»(ref-277990-S39481802672008012100000)
24. «Interior Backlighting Does Not Dim»(ref-277990-S40469557872008012100000)
25. «Interior Backlighting Inoperative»(ref-277990-S20925175302008012100000)
26. «Park, License, and Tail Lamps Always On»(ref-277990-S28505152002008012100000)
27. «Park, License, and Tail Lamps Inoperative»(ref-277990-S16538454702008012100000)
28. «Reading Lamp(s) Inoperative»(ref-277990-S39767259532008012100000)
29. «Roof Beacon Lamp Always On»(ref-277990-S24307909212008012100000)
30. «Roof Beacon Lamp Inoperative»(ref-277990-S21564170422008012100000)
31. «Stop Lamps Always On»(ref-277990-S22329816532008012100000)
32. «Stop Lamps Inoperative»(ref-277990-S30344992592008012100000)
33. «Turn Signal Lamps and/or Indicators Always On or Flashing»(ref-277990-S03499486922008012100000)
34. «Turn Signal Lamps and/or Indicators Inoperative»(ref-277990-S41792312952008012100000)
35. «Vanity Mirror Lamp(s) Inoperative»(ref-277990-S25552759472008012100000)

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

High Mount Stop Lamp Malfunction

1. Ignition OFF, disconnect the X5 harness connector at the underhood fuse block.
2. Connect a test lamp between the CHMSL relay control circuit terminal K6 and ground at the harness connector.
3. Apply the brake pedal ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
4. Ignition OFF, reconnect the X5 harness connctor to the underhood fuse block. Disconnect the harness connector at the center high mounted stop lamp (CHMSL).
5. Test for less than 1.0 ohm of resistance between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for and open/high resistance.
6. Connect a test lamp between the CHMSL control circuit terminal A and ground.
7. Apply the brake pedal ON and OFF. 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 an short to ground. If the circuit tests normal, replace the CHMSL.
8. If all circuits test normal, test or replace the CHMSL.

Component Testing

Center High Mounted Stop Lamp (CHMSL)

1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Install a 15A fused jumper wire between the control circuit terminal A and 12 volts. Install a jumper wire between the ground circuit terminal B and ground. Verify that the CHMSL illuminates. If the CHMSL does not completely illuminate, test or replace the inoperative bulb or CHMSL.

Diagnostic Aids

If only the right front turn signal is inoperative check for an open CTSY fuse in the I/P fuse block. If the fuse is open refer to Courtesy Lamps Inoperative .

Turn Signal Lamps and/or Indicators Inoperative