Buick Regal Owners & Service Manuals
Buick Regal 2018-2024 Service Manual / Accessories and Equipment / Power Seats / Diagnostic Information and Procedures / Lumbar/Bolster/Massage Malfunction (AVK without AF6 or AVU without AKE)

Buick Regal: Lumbar/Bolster/Massage Malfunction (AVK without AF6 or AVU without AKE)

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

Power Seats

1. The seat lumbar support functions are inoperative
2. The seat lumbar support pump is always ON

Circuit/System Description

The seat lumbar support valve assembly supplies the seat lumbar support switch with a signal and low reference circuits. When a lumbar switch is pressed, the signal circuit from the seat lumbar support valve assembly is pulled low through the switch contacts and series of resistors indicating the lumbar support request. In response to this request, the lumbar adjuster valve assembly energizes its internal inflate solenoid and applies battery voltage through the lumbar support pump control circuit to the pump. The pump runs to inflate the appropriate support bladder until the switch is released.

Reference Information

Schematic Reference

  • Driver Seat Wiring Schematics
  • Passenger Seat Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Lumbar Support Description and Operation (With Memory Seat A44/A45) or Lumbar Support Description and Operation (Without Memory Seat A44/A45)

Electrical Information Reference

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

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate seat lumbar support valve assembly listed below. It may take up to 2 min for all vehicle systems to power down.

  • Q51D Seat Lumbar Support Valve Assembly - Driver
  • Q51P Seat Lumbar Support Valve Assembly - Passenger

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

  • 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. Ignition ON.

4. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.

  • If the test lamp does not illuminate
  1. Ignition OFF, remove the test lamp.
  2. Test for infinite resistance between the B+ 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 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.
  • Go to next step: If the test lamp illuminates

5. Ignition OFF and all vehicle systems OFF, connect the harness connector at the Q51 Seat Lumbar Support Valve Assembly and disconnect the harness connector at the S65 Seat Lumbar Support Switch. It may take up to 2 min for all vehicle systems to power down.

6. Test for less than 10 Ω between the low reference circuit terminal 1 and ground.

  • If 10 Ω or greater
  1. Ignition OFF.
  2. Test for less than 2 Ω in the low reference circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit
    • If less than 2 Ω, test or replace the Q51 Seat Lumbar Support Valve Assembly.
  • Go to next step: If less than 10 Ω

7. Ignition ON.

8. Test for 4.8 - 5.2 V between the signal circuit terminal 2 and ground.

  • If less than 4.8 V
  1. Ignition OFF, disconnect the harness connector at the Q51 Seat Lumbar Support Valve Assembly.
  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, test or replace the Q51 Seat Lumbar Support Valve Assembly.
  • If greater than 5.2 V
  1. Ignition OFF, disconnect the harness connector at the Q51 Seat Lumbar Support Valve Assembly, ignition ON.
  2. Test for less than 1 V between the signal circuit and ground.
    • If 1 V or greater, repair the short to voltage on the circuit.
    • If less than 1 V, test or replace the Q51 Seat Lumbar Support Valve Assembly.
  • Go to next step: If between 4.8 - 5.2 V

9. Ignition OFF, connect the harness connector at the S65 Seat Lumbar Support Switch and disconnect the harness connector at the Q51 Seat Lumbar Support Valve Assembly.

10. Connect a DDM between the signal circuit terminal 4 and the low reference circuit terminal 5.

11. Test for the resistance values listed below while pressing the appropriate S65 Seat Lumbar Support Switch.

  • 146 - 178 Ω for the lumbar forward switch
  • 459 - 561 Ω for the lumbar rearward switch
  • 1134 - 1386 Ω for the lumbar down switch
  • 3024 - 3696 Ω for the lumbar up switch
  • If not between the specified values

Test or replace the S65 Seat Lumbar Support Switch.

  • Go to next step: If between the specified values

12. Ignition OFF, connect the harness connector at the Q51 Seat Lumbar Support Valve Assembly and disconnect the harness connector at the G31 Seat Lumbar/Bolster Pump.

13. Test for less than 10 Ω between the ground circuit terminal 2 and ground.

  • 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

14. Connect a test lamp between the control circuit terminal 1 and ground, ignition ON.

15. Verify the test lamp turns ON and OFF when pressing and releasing the lumbar forward switch.

  • If the test lamp remains OFF
  1. Ignition OFF, remove the test lamp, disconnect the harness connector at the Q51 Seat Lumbar Support Valve Assembly.
  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, test or replace the Q51 Seat Lumbar Support Valve Assembly.
  • If the test lamp is always ON
  1. Ignition OFF, remove the teat lamp, disconnect the harness connector at the Q51 Seat Lumbar Support Valve Assembly, ignition ON.
  2. Test for less than 1 V between the control circuit and ground.
    • If 1 V or greater, repair the short to voltage on the circuit.
    • If less than 1 V, replace the Q51 Seat Lumbar Support Valve Assembly.
  • Go to next step: If the test lamp turns ON and OFF

16. Test or replace the G31 Seat Lumbar/Bolster Pump.

Component Testing

Seat Lumbar Support Switch

1. Ignition OFF, disconnect the harness connector at the appropriate S65 Seat Lumbar Support Switch.

2. Test for infinite resistance between the signal terminal 2 and the low reference terminal 1 with the switch in the open position.

  • If less than infinite resistance

Replace the S65 Seat Lumbar Support Switch.

  • Go to next step: If infinite resistance

3. Test for 146 - 178 Ω between the signal terminal 2 and the low reference terminal 1 while pressing the lumbar forward switch.

  • If not between 146 - 178 Ω

Replace the S65 Seat Lumbar Support Switch.

  • Go to next step: If between 146 - 178 Ω

4. Test for 459 - 561 Ω between the signal terminal 2 and the low reference terminal 1 while pressing the lumbar rearward switch.

  • If not between 459 - 561 Ω

Replace the S65 Seat Lumbar Support Switch.

  • Go to next step: If between 459 - 561 Ω

5. Test for 1134 - 1386 Ω between the signal terminal 2 and the low reference terminal 1 while pressing the lumbar down switch.

  • If not between 1134 - 1386 Ω

Replace the S65 Seat Lumbar Support Switch.

  • Go to next step: If between 1134 - 1386 Ω

6. Test for 3.02k - 3.7 kΩ between the signal terminal 2 and the low reference terminal 1 while pressing the lumbar up switch.

  • If not between 3.02k - 3.7 kΩ

Replace the S65 Seat Lumbar Support Switch.

  • Go to next step: If between 3.02k - 3.7 kΩ

7. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

  • Driver or Passenger Seat Lumbar Control Switch Replacement
  • Front Seat Back Lumbar Replacement (2 Way) or Front Seat Back Lumbar Replacement (GS) or Front Seat Back Lumbar Replacement (4 Way)

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