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
Power seat lumbar support is completely controlled through the seat lumbar support switch. Battery voltage is supplied at all times to the lumbar switch through a 25 A circuit breaker located in the rear 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 Driver Seat Schematics
* Passenger Seat Schematics Passenger Seat Schematics
Connector End View Reference
Component Connector End Views Connector End Views By Name
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 5 Ohms between the ground circuit terminals listed below and ground:
* Terminal A
* Terminal C
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal D and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Ignition OFF, connect the harness connector at the S65 seat lumbar support switch and disconnect the harness connector at the M53 seat lumbar support motor.
5. Ignition ON, verify that a test lamp illuminates between control circuit terminal A and control circuit terminal B while pressing the lumbar switch in both directions.
• If the test lamp does not illuminate for either direction, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal replace the S65 seat lumbar support switch.
6. If the circuits test normal replace the M53 seat lumbar support motor.
Component Testing
S65 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 each control terminal listed below with the switch in the open position.
* Lumbar horizontal forward switch terminal B
* Lumbar horizontal rearward switch terminal E
• If not the specified value, replace the S65 seat lumbar support switch.
3. Test for less than 1 Ohms between the B+ terminal D and each control terminal listed below with the appropriate switch in the closed position.
* Lumbar horizontal forward switch terminal B
* Lumbar horizontal rearward switch terminal E
• If greater than the specified range, replace the S65 seat lumbar support switch.
4. Test for less than 1 Ohms between each control terminal and the ground terminal listed below with the switch in the open position.
* Lumbar horizontal forward switch terminal B and terminal C
* Lumbar horizontal rearward switch terminal E and terminal A
• If greater than the specified range, replace the S65 seat lumbar support switch.
M53 Seat Lumbar Support Motor
1. Ignition OFF, disconnect the harness connector at the M53 seat lumbar support 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 the control terminal B and 12 V. Momentarily install a jumper wire between the control terminal A and ground. The M53 seat lumbar support motor should momentarily perform the FORWARD function.
• If the function does not perform as specified, replace the M53 seat lumbar support motor.
3. Reverse the polarity of jumper wires; the lumbar motor should perform REARWARD function.
• If the function does not perform as specified, replace the M53 seat lumbar support motor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Driver Seat Lumbar Control Switch Replacement Driver Seat Lumbar Control Switch Replacement
* Passenger Seat Lumbar Control Switch Replacement Passenger Seat Lumbar Control Switch Replacement
* Driver or Passenger Seat Lumbar Support Replacement Driver or Passenger Seat Lumbar Support Replacement