Buick Regal: Turn Signal Lamps and/or Indicators Malfunction

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.

Diagnostic Fault Information

1. Turn Signal Lamps and/or Indicators Malfunction
2. Turn Signal/Multifunction Switch Malfunction
3. Turn Signal Lamp Outage Detection Malfunction

Circuit/System Description

Ground is applied at all times to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START positions. 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 responds to the turn signal switch input by applying a pulsating voltage to the front and rear turn signal lamps through there respective control circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective turn signal indicator be pulsed ON and OFF.

Diagnostic Aids

When replacing a headlamp assembly, the following control modules located on each headlamp assembly are serviceable.

• K189L Headlamp/Cornering Lamp Control Module - Left
• K189R Headlamp/Cornering Lamp Control Module - Right
• K26L Headlamp Control Module - Left
• K26R Headlamp Control Module - Right

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

1. Ignition ON.

2. Verify the scan tool Right Turn Signal Switch and Left Turn Signal Switch parameters change between Active and Inactive while cycling the turn signal switch between the right and left positions.

• If the parameters do not change

Refer to Circuit/System Testing - Turn Signal/Multifunction Switch Malfunction.

• Go to next step: If the parameters change

3. Verify the left front turn signal lamps turn ON and OFF while commanding the Left Front Turn Signal Lamp ON and OFF with a scan tool.

• If the left front turn signal lamps do not turn ON and OFF

Refer to Circuit/System Testing - Turn Signal Lamps Malfunction.

• Go to next step: If the left front turn signal lamps turn ON and OFF

4. Verify the right front turn signal lamps turn ON and OFF while commanding the Right Front Turn Signal Lamp ON and OFF with a scan tool.

• If the right front turn signal lamps do not turn ON and OFF

Refer to Circuit/System Testing - Turn Signal Lamps Malfunction.

• Go to next step: If the right front turn signal lamps turn ON and OFF

5. Verify the left rear turn signal lamp turns ON and OFF while commanding the Left Rear Turn Signal Lamp ON and OFF with a scan tool.

• If the left rear turn signal lamp does not turn ON and OFF

Refer to Circuit/System Testing - Turn Signal Lamps Malfunction.

• Go to next step: If the left rear turn signal lamp turns ON and OFF

6. Verify the right rear turn signal lamp turns ON and OFF while commanding the Right Rear Turn

• Signal Lamp ON and OFF with a scan tool.

If the right rear turn signal lamp does not turn ON and OFF

• Go to next step: If the right rear turn signal lamp turns ON and OFF

7. Observe the left and right turn signal lamps and turn signal indicators on the instrument cluster while activating the left and right turn signals. The left and right turn signal lamps and indicators should illuminate and flash at a normal rate when turned ON.

• If the left and right turn signal lamps and indictors illuminate but flash in a rapid manner

Refer to Circuit/System Testing - Turn Signal Lamp Outage Detection Malfunction.

• Go to next step: If the left and right turn signal lamps and indictors operate normally

8. All OK.

Circuit/System Testing

Turn Signal/Multifunction Switch Malfunction

1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, open and close driver door, disconnect the harness connector at the S78 Turn Signal/Multifunction Switch. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 15 Ω between the ground circuit terminal 3 and ground.

• If 15 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 15 Ω

3. Ignition ON.

4. Verify the scan tool Left Turn Signal Switch parameter is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.

6. Verify the scan tool Left Turn Signal Switch parameter is Active.

• If not Active

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 1 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If Active

7. Verify the scan tool Right Turn Signal Switch parameter is Inactive.

If not Inactive

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 2 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

8. Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground.

9. Verify the scan tool Right Turn Signal Switch parameter is Active.

• If not Active

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 2 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If Active

10. Test or replace the S78 Turn Signal/Multifunction Switch.

Turn Signal Lamps Malfunction

1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate component listed below. It may take up to 2 min for all vehicle systems to power down.

• E4Y Turn Signal Repeater Lamp - Left
• E4Z Turn Signal Repeater Lamp - Right
• E13LA Headlamp Assembly - Left
• E13RA Headlamp Assembly - Right
• E42L Tail Lamp Assembly - Left
• E42R Tail Lamp Assembly - Right

2. Test for less than 10 Ω between the appropriate ground circuit terminal listed below and ground.

• E4Y Turn Signal Repeater Lamp - Left terminal 1
• E4Z Turn Signal Repeater Lamp - Right terminal 1
• E13LA Headlamp Assembly - Left terminal 1 (with T4A)
• E13RA Headlamp Assembly - Right terminal 1 (with T4A)
• E13LA Headlamp Assembly - Left terminal 2 (with T4L)
• E13RA Headlamp Assembly - Right terminal 2 (with T4L)
• E42L Tail Lamp Assembly - Left terminal 4
• E42R Tail Lamp Assembly - Right terminal 4
• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.

• E4Y Turn Signal Repeater Lamp - Left terminal 2
• E4Z Turn Signal Repeater Lamp - Right terminal 2
• E13LA Headlamp Assembly - Left terminal 5
• E13RA Headlamp Assembly - Right terminal 5
• E42L Tail Lamp Assembly - Left terminal 2
• E42R Tail Lamp Assembly - Right terminal 2

4. Verify the test lamp turns ON and OFF when commanding the appropriate Turn Signal Lamp ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
   • X4 right turn signals
   • X5 left turn signals
2. Test for infinite resistance between the control circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
   • X4 right turn signals
   • X5 left turn signals
2. Test for less than 1 V between the control circuit terminal and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

5. Test or replace the turn signal lamp.

Turn Signal Lamp Outage Detection Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly, ignition ON.

2. Test for B+ between the signal circuit terminal 10 and ground.

• If not B+

1. Ignition OFF, disconnect the X6 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 10 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If B+

3. Verify a test lamp does not illuminate between the signal circuit terminal 10 and ground.

• If the test lamp illuminates

1. Ignition OFF, disconnect the X6 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 10 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp does not illuminate

4. Test or replace the E13 Headlamp Assembly.

Turn Signal Indicators Malfunction

1. Ignition ON.

2. Verify the left and right turn signal indicators turn ON and OFF while commanding the All Indicators Test ON and OFF with a scan tool.

• If the left or right turn signal indictors are always OFF or remain ON

Replace the P16 Instrument Cluster.

• Go to next step: If the left and right turn signal indictors turn ON and OFF

3. Replace the K9 Body Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Turn Signal Switch Replacement
• Front Side Turn Signal Lamp Replacement
• Headlamp Replacement
• Rear Body Structure Stop Lamp Replacement (5-Door Hatchback 68) Rear Body Structure Stop Lamp Replacement (5-Door Wagon 35)
• Control Module References for BCM replacement, programming, and setup

Turn Signal Lamps and/or Indicators Malfunction

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.

Diagnostic Fault Information

1. Turn Signal Lamps and/or Indicators Malfunction
2. Turn Signal/Multifunction Switch Malfunction
3. Turn Signal Lamp Outage Detection Malfunction

Circuit/System Description

Ground is applied at all times to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START positions. 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 responds to the turn signal switch input by applying a pulsating voltage to the front and rear turn signal lamps through there respective control circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective turn signal indicator be pulsed ON and OFF.

Diagnostic Aids

When testing at the turn signal lamp bulb socket, make sure all measurements and test lamp connections are in the correct terminal location and do not come in contact with each other during testing.

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

1. Ignition ON.

2. Verify the scan tool Right Turn Signal Switch and Left Turn Signal Switch parameters change between Active and Inactive while cycling the turn signal switch between the right and left positions.

• If the parameters do not change

Refer to Turn Signal/Multifunction Switch Malfunction.

• Go to next step: If the parameters change

3. Verify the left front turn signal lamps turn ON and OFF while commanding the Left Front Turn Signal Lamp ON and OFF with a scan tool.

• If the left front turn signal lamps do not turn ON and OFF

Refer to Turn Signal Lamps Malfunction.

• Go to next step: If the left front turn signal lamps turn ON and OFF

4. Verify the right front turn signal lamps turn ON and OFF while commanding the Right Front Turn Signal Lamp ON and OFF with a scan tool.

• If the right front turn signal lamps do not turn ON and OFF

Refer to Turn Signal Lamps Malfunction.

• Go to next step: If the right front turn signal lamps turn ON and OFF

5. Verify the left rear turn signal lamp turns ON and OFF while commanding the Left Rear Turn Signal/Stop Lamp ON and OFF with a scan tool.

• If the left rear turn signal lamp does not turn ON and OFF

Refer to Turn Signal Lamps Malfunction.

• Go to next step: If the left rear turn signal lamp turns ON and OFF

6. Verify the right rear turn signal lamp turns ON and OFF while commanding the Right Rear Turn Signal/Stop Lamp ON and OFF with a scan tool.

• If the right rear turn signal lamp does not turn ON and OFF

Refer to Turn Signal Lamps Malfunction.

• Go to next step: If the right rear turn signal lamp turns ON and OFF

7. Observe the left and right turn signal lamps and turn signal indicators on the instrument cluster while activating the left and right turn signals. The left and right turn signal lamps and indicators should illuminate and flash at a normal rate when turned ON.

• If the left and right turn signal lamps and indictors illuminate but flash in a rapid manner

Refer to Turn Signal Lamp Outage Detection Malfunction.

• Go to next step: If the left and right turn signal lamps and indictors operate normally

8. All OK.

Circuit/System Testing

Turn Signal/Multifunction Switch Malfunction

1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, open and close driver door, disconnect the harness connector at the S78 Turn Signal/Multifunction Switch. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 15 Ω between the ground circuit terminal 3 and ground.

• If 15 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 15 Ω

3. Ignition ON.

4. Verify the scan tool Left Turn Signal Switch parameter is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.

6. Verify the scan tool Left Turn Signal Switch parameter is Active.

• If not Active

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 1 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If Active

7. Verify the scan tool Right Turn Signal Switch parameter is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 2 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

8. Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground.

9. Verify the scan tool Right Turn Signal Switch parameter is Active.

• If not Active

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 2 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If Active

10. Test or replace the S78 Turn Signal/Multifunction Switch.

Turn Signal Lamps Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.

2. Verify a test lamp illuminates between the B+ circuit terminal 3 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, remove the F8DA fuse at the X51A Fuse Block - Instrument Panel.
2. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, remove the F8DA fuse at the X51A Fuse Block - Instrument Panel.
2. Test for infinite resistance between the B+ circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If the test lamp illuminates

3. Ignition OFF, connect the X1 harness connector at the K9 Body Control Module.

4. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate component listed below. It may take up to 2 min for all vehicle systems to power down.

• A9A Outside Rearview Mirror - Driver
• A9B Outside Rearview Mirror - Passenger
• E4LF Turn Signal Lamp - Left Front
• E4RF Park/Turn Signal Lamp - Right Front
• E4LR Turn Signal Lamp - Left Rear
• E4RR Turn Signal Lamp - Right Rear

5. Test for less than 15 Ω between the appropriate ground circuit terminal listed below and ground.

• A9A Outside Rearview Mirror - Driver terminal 5 (with DWK)
• A9B Outside Rearview Mirror - Passenger terminal 5 (with DWK)
• E4LF Turn Signal Lamp - Left Front terminal G
• E4RF Turn Signal Lamp - Right Front terminal G
• E4LR Turn Signal Lamp - Left Rear terminal B
• E4RR Turn Signal Lamp - Right Rear B
• If 15 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 15 Ω

6. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.

• A9A Outside Rearview Mirror - Driver terminal 13
• A9B Outside Rearview Mirror - Passenger terminal 13
• E4LF Turn Signal Lamp - Left Front terminal A
• E4RF Turn Signal Lamp - Right Front terminal A
• E4LR Turn Signal Lamp - Left Rear terminal A
• E4RR Turn Signal Lamp - Right Rear A

7. Verify the test lamp turns ON and OFF when commanding the appropriate Turn Signal Lamp ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
2. X5 left turn signals
3. X4 right turn signals
4. Test for infinite resistance between the control circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
5. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
   • X5 left turn signals
   • X4 right turn signals
2. Test for less than 1 V between the control circuit terminal and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

8. Test or replace the turn signal lamp.

Turn Signal Lamp Outage Detection Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate component listed below, ignition ON.

• E13LA Headlamp Assembly - Left
• E13RA Headlamp Assembly - Right

2. Test for B+ between the appropriate signal circuit terminal listed below and ground.

• E13LA Headlamp Assembly - Left terminal 3
• E13RA Headlamp Assembly - Right terminal 3
• If not B+

1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If B+

3. Verify a test lamp does not illuminate between the appropriate signal circuit terminal listed below and ground.

• E13LA Headlamp Assembly - Left terminal 3
• E13RA Headlamp Assembly - Right terminal 3
• If the test lamp illuminates

1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp does not illuminate

4. Test or replace the turn signal lamp.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Turn Signal Switch Replacement
• Front Side Turn Signal Lamp Replacement
• Rear Body Structure Stop Lamp Replacement (5-Door Hatchback 68) Rear Body Structure
• Stop Lamp Replacement (5-Door Wagon 35)
• Rear Body Structure Stop Lamp Replacement (5-Door Hatchback 68) or Rear Body Structure Stop Lamp Replacement (5-Door Wagon 35)
• Control Module References for BCM replacement, programming, and setup

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