Buick Regal: DTC B3950 or B3951

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B3950 01

Left Rear Turn Signal Circuit Short to Battery

DTC B3950 02

Left Rear Turn Signal Circuit Short to Ground

DTC B3950 04

Left Rear Turn Signal Circuit Open

DTC B3951 01

Right Rear Turn Signal Circuit Short to Battery

DTC B3951 02

Right Rear Turn Signal Circuit Short to Ground

DTC B3951 04

Right Rear Turn Signal Circuit Open

Diagnostic Fault Information

Circuit/System Description

Ground is applied at all times to the turn signal/multifunction switch. When the turn signal/multifunction switch is placed in either the turn right or turn left position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM then applies a voltage to the front/side and rear turn signal lamps through their respective voltage supply circuits.

Conditions for Running the DTC

B3950 01 and B3951 01

The appropriate turn signal is inactive

B3950 02, B3950 04, B3951 02 or B3951 04

The appropriate turn signal is active

Conditions for Setting the DTC

B3950 01 or B3951 01

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

B3950 02 or B3951 02

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

B3950 04 or B3951 04

The BCM detects an open control circuit.

Action Taken When the DTC Sets

The appropriate turn signal lamp is inoperative.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

Ignition ON, perform the appropriate Rear Turn Signal/Hazard Lamp test. The appropriate rear turn signal/hazard lamp should be ON/OFF.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.

2. Test for less than 5 Ω between the appropriate turn signal lamp ground circuit harness connector listed below and ground.

• E42R Tail Lamp Assembly - Right ground circuit harness connector terminal 4
• E42L Tail Lamp Assembly - Left ground circuit harness connector terminal 4
• If greater than the specified value, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the appropriate turn signal lamp control circuit harness connector listed below and ground.

• E42R Tail Lamp Assembly - Right ground circuit harness connector terminal 2
• E42L Tail Lamp Assembly - Left ground circuit harness connector terminal 2

4. Command the appropriate turn signal lamp test 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 signal circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
• If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K9 Body Control Module.

5. If all the circuits test normal, replace the appropriate turn signal lamp.

Repair Instructions

• Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  Tail Lamp Replacement (5-Door Hatchback 68) Tail Lamp Replacement (5-Door Wagon 35)

• Control Module References for BCM replacement, setup and programming

DTC C0010

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC C0010 5A

Reverse Gear Signal Circuit Not Plausible

Diagnostic Fault Information

Circuit/System Description

When the transmission is placed in the reverse position, the engine control module (ECM) 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 battery voltage to the backup lamps. The backup lamps are permanently grounded. Once the driver moves the gear selector out of the reverse position, a message is sent by the ECM via serial data requesting the BCM to remove battery voltage from the backup lamp control circuit.

Conditions for Running the DTC

The vehicle is driving in forward or reverse direction.

Conditions for Setting the DTC

The control module detects a stucking backup lamp switch.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

Ignition ON, perform the Backup Lamps Relay Command test. The backup lamp should be ON/OFF

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B16 Backup Lamp Switch.

2. Disconnect the negative terminal of the C1 Battery.

3. Test for less than 5 Ω between the ground circuit harness connector terminal 2 and ground.

• If greater than the specified value, test the ground circuit for an open/high resistance.

4. Reconnect the negative terminal to the C1 Battery.

5. Disconnect the X2 harness connector at the K20 Engine Control Module.

6. ignition On, test for less than 0.3 V at the B16 Backup Lamp Switch signal circuit harness connector terminal 1 and ground.

• If greater than the specified value, test the signal circuit for a short to voltage.

7. Ignition OFF, test for infinite resistance between the B16 Backup Lamp Switch signal circuit harness connector 1 and ground.

• If lower than the specified value, test the signal circuit for a short to ground.

8. Connect the harness connector at the B16 Backup Lamp Switch.

9. Disconnect the negative terminal of the C1 Battery.

10. Reversing gear engaged, test for less than 5 Ω between the K20 Engine Control Module X2 harness connector terminal listed below and ground:

• Terminal 34 with LBY
• Terminal 75 with LCD, LBX or LBS
• Terminal 28 with LDE or 2H0
• Terminal 18 with LDK or LBW
• Terminal 82 with LLU
• If greater than the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, test or replace the B16 Backup Lamp Switch.

11. Reversing gear disengaged, test for infinite resistance between the K20 Engine Control Module X2 harness connector terminal listed below and ground:

• Terminal 34 with LBY
• Terminal 75 with LCD, LBX or LBS
• Terminal 28 with LDE or 2H0
• Terminal 18 with LDK or LBW
• Terminal 82 with LLU
• If lower than the specified value, test or replace the B16 Backup Lamp Switch.

12. If all the circuits test normal, replace the K20 Engine Control Module.

Component Testing

Static Test

1. Ignition OFF, disconnect the harness connector at the B16 Backup Lamp Switch. Reversing gear engaged, test for less than 5 Ω at the B16 Backup Lamp Switch terminal 1 and terminal 2.

• If greater than the specified value replace the B16 Backup Lamp Switch.

2. Reversing gear disengaged, test for infinite resistance at the B16 Backup Lamp Switch terminal 1 and terminal 2.

• If less than the specified value replace the B16 Backup Lamp Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Tail Lamp Replacement (5-Door Hatchback 68) Tail Lamp Replacement (5-Door Wagon 35)
• High Mount Stop Lamp Replacement (Wagon) High Mount Stop Lamp Replacement (Hatchback)
• Control Module References for BCM replacement, setup and programming

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