Lumbar Support Inoperative

Lumbar Support Inoperative

Diagnostic Instructions

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



Circuit/System Description

The power lumbar system is controlled through the power lumbar switch. Battery voltage is supplied to the power lumbar switch through the SEATSW 40A fuse in the underhood BEC and the Power Seats 20A circuit breaker in the driver seat wiring harness. While the lumbar switch is in an inactive state the switch contacts are closed to the lumbar switch ground circuit. When a lumbar switch is pressed to an active state the switch contact is closed to the battery voltage supply circuit. The lumbar adjuster motor is controlled by the lumbar switch through 2 motor control circuits. The lumbar adjuster motor is bidirectional and the direction of adjuster motor rotation is determined by which of the motor control circuits is switched to battery voltage while the other remains grounded.


Reference Information
Schematic Reference

* Driver Seat Schematics (Driver Seat Schematics)
* Passenger Seat Schematics (Passenger Seat Schematics)

Connector End View Reference

Component Connector End Views (Component Connector End Views)
Description and Operation

* Power Seats System Description and Operation (Power Seats System Description and Operation)
* Lumbar Support Description and Operation (Lumbar Support Description and Operation)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Testing

1. Disconnect the harness connector at the lumbar adjuster switch.
2. Test for less than 1 ohm of resistance between the ground circuit terminal A and ground.

• If greater than 1 ohm, test the ground circuit for an open/high resistance.

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

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Connect the harness connector at the lumbar adjuster switch.
5. Disconnect the harness connector at the lumbar motor assembly.
6. Connect a test lamp between the motor control circuit terminals.
7. Verify that the test lamp illuminates while pressing the lumbar switch in both directions.

• If the test lamp does not illuminate for both directions, test the motor circuits for a short to ground or an open/high resistance. If the circuits test normal replace the lumbar adjuster switch.

8. If the circuits test normal replace the lumbar motor assembly.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Lumbar Switch Replacement (Lumbar Switch Replacement)
* Front Seat Lumbar Support Replacement (Front Seat Lumbar Support Replacement)