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Lumbar Support Malfunction




Lumbar Support Malfunction

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.

Diagnostic Fault Information






Circuit/System Description

Battery voltage is supplied at all times to the seat lumbar support switch through a 20 A fuse located in the underhood fuse block. When the lumbar switches are in an inactive state, the switch contacts are closed to the switch ground circuit.

The lumbar motor is reversible. For example, when the lumbar forward switch is pressed to move the lumbar support forward, battery voltage is applied through the switch contacts and the lumbar motor forward control circuit to the motor. The motor is grounded through the lumbar motor rearward switch contacts and the lumbar motor rearward control circuit to the motor. The motor runs in order to drive the lumbar support forward toward the occupants back until the switch is released. Moving the lumbar support rearward works similarly to moving the lumbar support forward, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction.

Reference Information

Schematic Reference

Driver Seat Schematics [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Sunshade - Left Front

Description and Operation

Lumbar Support Description and Operation Lumbar Support

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Circuit/System Testing

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

2. Test for less than 10 omhs between the ground circuit terminals listed below and ground.

* Terminal A

* Terminal C

• If 10 omhs or greater

1. Ignition OFF.

2. Test for less than 2 omhs in the ground circuit end to end.

• If 2 omhs or greater, repair the open/high resistance in the circuit.

• If less than 2 omhs, repair the open/high resistance in the ground connection.

• If less than 10 omhs

3. Ignition ON.

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

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

1. Ignition OFF.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, 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.

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, test or replace the M52 Seat Lumbar Support Horizontal Motor.

• If the test lamp illuminates

5. Ignition OFF, connect the harness connector at the S65 Seat Lumbar Support Switch and disconnect the harness connector at the M52 Seat Lumbar Support Horizontal Motor.

6. Connect a test lamp between control circuit terminal A and control circuit terminal B.

7. Verify the test lamp turns ON when commanding the M52D Driver Seat Lumbar Support Horizontal Motor Forward and Rearward using the S65 Seat Lumbar Support Switch.

• If the test lamp remains OFF during either of the commands

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

2. Test for less than 2 ohms in each control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, test or replace the S65 Seat Lumbar Support Switch.

• If the test lamp turns ON during each of the commands

8. Test or replace the M52 Seat Lumbar Support Horizontal Motor.

Component Testing

Seat Lumbar Support Switch

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

2. Test for infinite resistance between the B+ terminal D and the control terminals listed below with the switch in the open position.

* Terminal B

* Terminal E

• If less than infinite resistance
Replace the S65 Seat Lumbar Support Switch.

3. Test for less than 2 omhs between the B+ terminal D and the control terminals listed below with the appropriate switch in the closed position.

* Terminal B

* Terminal E

• If 2 omhs or greater
Replace the S65 Seat Lumbar Support Switch.

• If less than 2 omhs

4. Test for less than 2 omhs between the ground and control terminals listed below with the switch in the open position.

* Terminal A and terminal B

* Terminal C and terminal E

• If 2 omhs or greater
Replace the S65 Seat Lumbar Support Switch.

• If less than 2 omhs

5. All OK.

Seat Lumbar Support Horizontal Motor

1. Ignition OFF, disconnect the harness connector at the M52 Seat Lumbar Support Horizontal Motor.

Note: When performing the following tests, make sure that the lumbar support is not already in the position the test is attempting to produce.

2. Install a 30♦A fused jumper wire between control terminal A and 12 V.

3. Momentarily install a jumper wire between control terminal B and ground. The lumbar support motor should momentarily perform the appropriate FORWARD/ REARWARD function.

• If the motor does not perform the FORWARD/ REARWARD function
Replace the motor.

• If the motor performs the FORWARD/ REARWARD function

4. Reverse the jumper wires; the motor should perform FORWARD/ REARWARD function.

• If the motor does not perform the FORWARD/ REARWARD function
Replace the motor.

• If the motor performs the FORWARD/ REARWARD function

5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Driver Seat Lumbar Control Switch Replacement Driver Seat Lumbar Control Switch Replacement

* Driver or Passenger Seat Lumbar Support Actuator Replacement Driver or Passenger Seat Lumbar Support Actuator Replacement

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