Lighting Systems: Diagnosis Chevrolet Uplander I

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

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

1. The identification of the control modules which command the system
2. The identification of any stored diagnostic trouble codes (DTCs) and their status

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

Scan Tool Output Controls

Body Control Module (BCM)

Scan Tool Data List

Scan Tool Data List

BCM Scan Tool Data Definitions

The body control module (BCM) Scan Tool Data Definitions contains a brief description of all Lighting System related BCM parameters available on the scan tool.

Circuit Description

When the body control module (BCM) receives a class 2 signal from the powertrain control module (PCM) or engine control module (ECM) indicating the gear selector is in the REVERSE position, the BCM applies positive voltage to the backup lamps supply voltage circuit. The backup lamps are grounded at G301 for the left backup lamp and G302 for the right backup lamp.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B2545 Backup Lamps Circuit

Conditions for Running the DTC

1. The battery voltage must be between 9-16 volts.
2. The gear selector must be placed in and out of the REVERSE position.

Conditions for Setting the DTC

1. When the CHMSL BACK/UP Fuse is open.
2. When the backup lamps supply voltage circuit is shorted to ground or shorted to voltages.
3. When the backup lamps supply voltage circuit is open before the first splice.
4. When circuit 1240 is open or shorted to voltage.

Action Taken When the DTC Sets

The backup lamps will not operate properly.

Conditions for Clearing the DTC

1. This DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

Diagnostic Aids

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections .

DTC B2545

When the body control module (BCM) receives a ground signal from the headlamp dimmer switch high beam signal circuit or flash-to-pass switch signal circuit requesting to illuminate the high beam headlamps, the BCM will energize the high beam relay by grounding the headlamp high beam relay control circuit.

This diagnostic procedure supports the following DTC

DTC B2580 Headlamp High Beam Control Circuit

1. The battery voltage must be between 9-16 volts.
2. Headlamp switch is in the ON position.
3. Headlamp high beam switch is cycled between high beams ON and OFF several times.

1. When the BCM does not activate the high beam relay and the headlamp high beam relay control circuit is shorted to ground
2. When the BCM activates the high beam relay and the headlamp high beam relay control circuit is shorted to voltage or open

The high beam headlamps will not operate or will remain always ON.

Conditions for Clearing the MIL/DTC

1. This DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

DTC B2580

The body control module (BCM) applies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp switch. When the switch is placed to the desired position, the dimmed voltage setting is applied from the interior lamp switch through the I/P dimming control circuit to the BCM. The BCM applies the dimmed voltage to the instrument panel lamp supply voltage circuit.

This diagnostic procedure supports the following DTC

DTC B2610 Passenger Compartment Dimming 1 Circuit

1. The battery voltage must be between 9-16 volts.
2. The ignition in the RUN position.
3. The headlamps into ON position.

1. When the BCM receives an I/P controls illumination lamp request signal and the I/P dimming voltage reference circuit is shorted to ground, open or short to battery positive voltage
2. When the BCM is not receiving an instrument panel controls illumination lamp request signal and the I/P dimming control circuit is shorted to battery positive voltage or open

The instrument panel illumination lamps and the controls illumination lamps will not operate or are always ON.

1. This DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC B2610

The body control module (BCM) monitors the daytime running lamps (DRL) ambient light sensor signal circuit in order to determine if the DRL or the headlamps should be turned ON in the automatic lamp control (ALC) mode. When the BCM senses the ambient light sensor voltage is between 1-4.9 volts, either the DRL or the headlamps will be commanded ON.

This diagnostic procedure supports the following DTC

DTC B2645 Ambient Light Sensor Circuit

The system voltage must be between 9-16 volts.

1. When the DRL ambient light sensor signal voltage is less than 1 volt
2. When the DRL ambient light sensor signal voltage is more than 4.9 volts

The headlamps will remain ON in any ambient light state during ALC mode.

1. This DTC will clear immediately after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

DTC B2645

The body control module (BCM) supplies battery positive voltage to the center high mounted stop lamp (CHMSL) through the stop lamp supply voltage circuit when the brakes are applied. The stop lamp supply voltage circuit also supplies a signal to the powertrain control module (PCM) or engine control module (ECM) and the electronic brake control module (EBCM) for other functions, is a separate pin in the BCM connector and is internally connected within the BCM.

This diagnostic procedure supports the following DTC

DTC B3445 Stop Lamp Circuit

1. The battery voltage must be between 9-16 volts.
2. The brake pedal must be applied.

1. When the BCM detects a short to ground in the stop lamp supply voltage circuit to the CHMSL.
2. When the BCM never detects an open, indicating a BCM fault.
3. When the BCM detects a short to ground in the stop lamp supply voltage circuit to another module.

The CHMSL will not operate.

1. This DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

1. Perform a visual inspection for loose or poor connections at all related components. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) .
2. A short to ground in either stop lamp supply voltage circuits (CHMSL or other module) may cause this DTC.

DTC B3445

The body control module (BCM) controls the park lamp relay through the park lamp relay control circuit. The BCM grounds the park lamp relay control circuit which energizes the park lamp relay.

This diagnostic procedure supports the following DTC

DTC B3838 Park Lamp Relay Control Circuit

The BCM must be commanding the park lamp relay to energize.

1. The BCM detects a short to battery positive voltage, a short to ground, a poor connection or an open in the park lamp relay control circuit when it is trying to energize the park lamp relay.
2. A short to ground in the park lamp supply voltage circuit
3. An open in the park lamp relay coil
4. The condition above must be present for more than 0.3 seconds.

The park lamps will not operate or will remain always ON.

1. A fault in the park lamp relay control circuit is no longer detected by the BCM when the park lamp relay is commanded to energize. After the fault is removed, the ignition must be cycled to clear a current code.
2. A short to ground in the park lamp supply voltage circuit is no longer detected by the BCM when the park lamp relay is commanded to energize. After the fault is removed, the ignition must be cycled to clear a current code.
3. A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
4. Current and history DTCs can be cleared using the scan tool.

If the DTC B3838 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC B3838

When the turn signal switch is placed in the left turn position, the body control module (BCM) cycles positive voltage ON and OFF to the LF turn signal lamp through the left front turn signal lamp supply voltage circuit. The front turn signal lamps illuminate steady for daytime running lamp (DRL) operation.

This diagnostic procedure supports the following DTC

DTC B3948 Left Front Turn Signal Circuit

1. The battery voltage must be between 9-16 volts.
2. Ignition switch in the RUN position.
3. Turn signal switch placed in the left turn position.

1. An open in the left front turn signal lamp supply voltage circuit is present for longer than 0.1 second.
2. An open LF turn signal bulb
3. An open in the ground circuit of the lamp
4. An open or short to ground in the battery positive voltage circuit from the STOP/TURN fuse in the instrument panel (I/P) fuse block

The left front turn signal lamp and DRL does not work.

1. The DTC will clear on current status after the condition for setting the fault is corrected.
2. A history code will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

1. An open or short to ground in the battery positive voltage circuit of the STOP/TURN fuse will cause all 4 turn signal DTCs.
2. Check the LF turn lamp bulb. If the bulb is open, DTC B3948 will be set.
3. If the DTC is a history DTC, the fault may be intermittent. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) in Wiring Systems.
4. An intermittent short to ground or an open in the following locations may cause an intermittent malfunction to occur: The BCM The underhood electrical center The left front turn signal lamp supply voltage circuit

DTC B3948

When the turn signal switch is placed in the right turn position, the body control module (BCM) cycles positive voltage ON and OFF to the RF turn signal lamp through the right front turn signal lamp supply voltage circuit. The front turn signal lamps illuminate steady for daytime running lamps (DRL) operation.

This diagnostic procedure supports the following DTC

DTC B3949 Right Front Turn Signal Circuit

1. The battery voltage must be between 9-16 volts.
2. Ignition switch is in the RUN position.
3. Turn signal switch is placed in the right turn position.

1. An open in the right turn signal lamp supply voltage circuit is present for longer than 0.1 second.
2. An open RF turn signal bulb
3. An open in the ground circuit of the lamp
4. An open or short to ground in the battery positive voltage circuit from the STOP/TURN fuse in the instrument panel (I/P) fuse block

The right front turn signal lamp and DRL does not work.

1. The DTC will clear on current status after the condition for setting the fault is corrected.
2. A history code will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

1. An open or short to ground in the battery positive voltage circuit of the STOP/TURN fuse will cause all 4 turn signal DTCs.
2. Check the RF turn lamp bulb. If the bulb is open, DTC B3948 will be set.
3. If the DTC is a history DTC, the fault may be interment. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) in Wiring Systems.
4. An interment short to ground or an open in the following locations may cause an intermittent malfunction to occur: The BCM The underhood electrical center The right front turn signal lamp supply voltage circuit

DTC B3949

When the turn signal switch is placed in the left turn position, the body control module (BCM) cycles positive voltage ON and OFF to the LR turn signal lamps through the left rear stop/turn lamp supply voltage circuit.

This diagnostic procedure supports the following DTC

DTC B3950 Left Rear Turn Signal Circuit

1. The battery voltage must be between 9-16 volts.
2. Ignition switch is in the RUN position.
3. Turn signal switch is in the left turn position.

1. An open in the left rear stop/turn lamp supply voltage circuit is present for longer than 0.1 second.
2. An open LR turn signal bulb
3. An open in the ground circuit of the lamp
4. An open or short to ground in the battery positive voltage circuit from the STOP/TURN fuse in the instrument panel (I/P) fuse block

The left rear turn signal lamp does not work.

1. The DTC will clear on current status after the condition for setting the fault is corrected.
2. A history code will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

1. An open or short to ground in the battery positive voltage circuit of the STOP/TURN fuse will cause all 4 turn signal DTCs.
2. Check the LR turn lamp bulb. If the bulb is open, DTC B3950 will be set.
3. If the DTC is a history DTC, the fault may be interment. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) in Wiring Systems.
4. An interment short to ground or an open in the following locations may cause an intermittent malfunction to occur: The BCM The left rear stop/turn lamp supply voltage circuit

DTC B3950

When the turn signal switch is placed in the right turn position, the body control module (BCM) cycles positive voltage ON and OFF to the RR turn signal lamps through the right rear stop/turn lamp supply voltage circuit.

This diagnostic procedure supports the following DTC

DTC B3951 Right Rear Turn Signal Circuit

1. The battery voltage must be between 9-16 volts.
2. Ignition switch is in the RUN position.
3. Turn signal switch is in the right turn position.

1. An open in the right rear stop/turn lamp supply voltage circuit is present for longer than 0.1 second.
2. An open in the RR turn signal bulb
3. An open in the ground circuit of the lamp
4. An open or short to ground in the battery positive voltage circuit from the STOP/TURN fuse in the instrument panel (I/P) fuse block

The right rear turn signal lamp does not work.

1. The DTC will clear on current status after the condition for setting the fault is corrected.
2. A history code will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

1. An open or short to ground in the battery positive voltage circuit of the STOP/TURN fuse will cause all 4 turn signal DTCs.
2. Check the RR turn lamp bulb. If the bulb is open, DTC B3950 will be set.
3. If the DTC is a history DTC, the fault may be interment. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) in Wiring Systems.
4. An interment short to ground or an open in the following locations may cause an intermittent malfunction to occur: The BCM The right rear stop/turn lamp supply voltage circuit

DTC B3951

The body control module (BCM) applies a ground through the brake pedal position sensor reference low circuit to the brake pedal position sensor. The BCM supplies a 10-volt reference through the brake sensor reference voltage circuit to the brake pedal position sensor. The brake pedal position sensor sends a variable voltage signal through the brake pedal position sensor signal circuit to the BCM as the brake pedal is applied.

This diagnostic procedure supports the following DTC

DTC C0277 Brake Pedal Position Sensor Circuit

The battery voltage must be between 9-16 volts.

1. A short to ground or a short to voltage in the brake pedal position sensor signal circuit is present.
2. A short to voltage, a short to ground or an open in the 10-volt reference circuit of the brake pedal position sensor
3. An open in the low reference circuit of the brake pedal position sensor
4. A malfunctioning brake pedal position sensor

The stop lamps may not function correctly.

1. The DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History and current DTC can be cleared using a scan tool.

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC C0277

The body control module (BCM) applies a ground through the brake pedal position sensor reference low circuit to the brake pedal position sensor. The BCM supplies a 10-volt reference through the brake sensor reference voltage circuit to the brake pedal position sensor. The brake pedal position sensor sends a variable voltage signal through the brake pedal position sensor signal circuit to the BCM as the brake pedal is applied.

This diagnostic procedure supports the following DTC

DTC C0278 Brake Pedal Position Sensor Not Calibrated

The battery voltage must be between 9-16 volts.

DTC C0278 will set if the brake position sensor is out of calibration.

The stop lamps may not function correctly

1. This DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles with out a fault present.
3. History and current DTCs can be cleared using a scan tool.

1. If DTC C0278 sets then recalibrate the brake position sensor.
2. Perform a visual inspection for a loose or poor connection at all related components. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) in Wiring Systems.

DTC C0278

The body control module (BCM) applies a ground through the brake pedal position sensor reference low circuit to the brake pedal position (BPP) sensor. The BCM supplies a 10-volt reference through the brake sensor reference voltage circuit to the BPP sensor. The BPP sensor sends a variable voltage signal through the BPP sensor signal circuit to the BCM as the brake pedal is applied.

This diagnostic procedure supports the following DTC

DTC C0283 Brake Pedal Position Sensor Circuit Low

The battery voltage must be between 9-16 volts.

1. A short to ground in the BPP sensor signal circuit is present.
2. A short to ground or an open in the 10-volt reference circuit of the BPP sensor
3. A malfunctioning BPP sensor

The stop lamps may not function correctly.

1. The DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History or current DTCs can be cleared using a scan tool.

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC C0283

The body control module (BCM) applies a ground through the brake pedal position sensor reference low circuit to the brake pedal position sensor. The BCM supplies a voltage signal through the 10-volt reference voltage circuit to the brake pedal position sensor. The brake pedal position sensor sends a variable voltage signal through the brake pedal position sensor signal circuit to the BCM as the brake pedal is applied.

This diagnostic procedure supports the following DTC

DTC C0870 Brake Pedal Position Sensor Reference Output Circuit

The battery voltage must be between 9-16 volts.

No change in the brake pedal position sensor signal to the BCM.

The stop lamps will not function correctly.

1. The DTC will clear on current status after the condition for setting the fault is corrected.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. History or current DTCs can be cleared using a scan tool.

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC C0870

The body control module (BCM) receives a signal from the brake pedal position sensor through the brake pedal position sensor signal circuit. The BCM then applies voltage through the stop lamp supply voltage circuit to the powertrain control module (PCM) or engine control module (ECM), electronic brake control module (EBCM) and the stop lamps.

This diagnostic procedure supports the following DTC

DTC P0572 Cruise Control Brake Pedal Position Sensor Circuit Low Voltage

1. The vehicle has cycled from 0-60 km/h (0-37 mph) 3 times in one ignition cycle.
2. Continuous once the previous criteria have been met.

The PCM/ECM detects low voltage on the stop lamp supply voltage circuit when the circuit should be battery positive voltage.

1. The PCM/ECM stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The PCM/ECM records the operating conditions at the time the diagnostic fails. The PCM/ECM stores this information in the Failure Records.

1. A last test failed or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

1. Verify that the brake pedal position sensor is adjusted properly. Refer to «Brake Pedal Position Sensor Calibration»(ref-241674-S24414319162006081100000) .
2. Test drive the vehicle if a switch or circuit condition cannot be located. An intermittent condition may be duplicated during a test drive.
3. For an intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) .

The body control module (BCM) receives a signal from the brake pedal position sensor through the brake pedal position sensor signal circuit. The BCM then applies voltage through the stop lamp supply voltage circuit to the powertrain control module (PCM) or engine control module (ECM), electronic brake control module (EBCM) and the stop lamps.

This diagnostic procedure supports the following DTC

DTC P0573 Cruise Brake Pedal Position Sensor Circuit High Voltage

1. Vehicle has cycled from 0-60 km/h (0-37 mph) 3 times in one ignition cycle.
2. Continuous once the previous criteria have been met.

The PCM/ECM detects a short to voltage on the brake pedal position sensor signal circuit when the voltage should be 0 volts.

1. The PCM/ECM stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The PCM/ECM records the operating conditions at the time the diagnostic fails. The PCM/ECM stores this information in the Failure Records.

1. A last test failed or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

1. Verify that the brake pedal position sensor switch is adjusted properly. Refer to «Brake Pedal Position Sensor Calibration»(ref-241674-S24414319162006081100000) .
2. Test drive the vehicle if a switch or circuit condition cannot be located. An intermittent condition may be duplicated during a test drive.
3. For an intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Lighting System. Refer to «Checking Aftermarket Accessories»(ref-241671-S33907418562006081100000) .
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 Inoperative»(ref-241674-S20379980372006081100000)
2. «Courtesy Lamps Always On»(ref-241674-S20951960472006081100000)
3. «Courtesy Lamps Inoperative»(ref-241674-S18068785392006081100000)
4. «Daytime Running Lamps (DRL) Defeat Inoperative»(ref-241674-S28382639982006081100000)
5. «Hazard Lamps Always On»(ref-241674-S38282844332006081100000)
6. «Hazard Lamps Inoperative»(ref-241674-S32168432112006081100000)
7. «Headlamps Always On - Low or High Beam»(ref-241674-S38244132262006081100000)
8. «Headlamps Inoperative - High Beams»(ref-241674-S36179235582006081100000)
9. «Headlamps Inoperative - Low Beams»(ref-241674-S08624452732006081100000)
10. «Headlamps Inoperative - Flash to Pass»(ref-241674-S09265205092006081100000)
11. «Illuminated Entry Lamps Inoperative»(ref-241674-S11601121762006081100000)
12. «Interior Backlighting Does Not Dim»(ref-241674-S19401994202006081100000)
13. «Interior Backlighting Inoperative»(ref-241674-S11840774732006081100000)
14. «Park, License and Tail Lamps Always On»(ref-241674-S22368632322006081100000)
15. «Park, License and Tail Lamps Inoperative»(ref-241674-S41481416542006081100000)
16. «Reading Lamp(s) Always On»(ref-241674-S26555790902006081100000)
17. «Reading Lamp(s) Inoperative»(ref-241674-S19262067972006081100000)
18. «Stop Lamps Always On»(ref-241674-S42140336252006081100000)
19. «Stop Lamps Inoperative»(ref-241674-S10527235892006081100000)
20. «Turn Signal Lamps and/or Indicators Always On or Flashing»(ref-241674-S20939443092006081100000)
21. «Turn Signal Lamps and/or Indicators Inoperative»(ref-241674-S04781360482006081100000)
22. «Vanity Mirror Lamp(s) Always On»(ref-241674-S38479978662006081100000)
23. «Vanity Mirror Lamp(s) Inoperative»(ref-241674-S28417533682006081100000)