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 without memory is completely controlled through the seat adjuster switch. Battery voltage is supplied at all times to the seat switches through a 20 A circuit breaker located in the I/P 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 horizontal 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 Fuel Pump and Level Sensor Assembly
Description and Operation
Power Seats System Description and Operation Description and Operation
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 appropriate S65 seat lumbar support switch.
2. Test for less than 5 ohms between the ground circuit terminal 4 and ground
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 2 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 lumbar support switch and disconnect the harness connector at the M53 seat lumbar support motor.
5. Connect a test lamp between control circuit terminal A and control circuit terminal B.
6. Ignition ON, command the lumbar support FORWARD and REARWARD using the lumbar switch. The test lamp should turn ON when commanding the FORWARD and REARWARD states.
• If the test lamp is always OFF during either of the commands, test the control circuits for a short to ground or an open high resistance. If the circuits test normal, test or replace the S65 seat lumbar support switch.
7. If all circuits test normal, test or replace the M53 seat lumbar support motor.
Component Testing
Lumbar Switch
1. Ignition OFF, disconnect the harness connector at the S65 seat lumbar support switch.
2. Test for infinite resistance the between B+ terminal 2 and each control terminal the with the switch in the open position.
• If not the specified value, replace the S65 seat lumbar support switch.
3. Test for less than 1 omhs between the B+ terminal 2 and each control terminal with the appropriate switch in the closed position.
• If greater than the specified range, replace the S65 seat lumbar support switch.
4. Test for less than 1 omhs between the ground terminal 1 and each control terminal with the switch in the open position.
• If greater than the specified range, replace the S65 seat lumbar support switch.
Lumbar 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 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. Momentarily install a jumper wire between control terminal B and ground. The lumbar motor should operate in the FORWARD direction.
• If the motor does not perform as specified, replace the M53 seat lumbar support motor.
3. Reverse the jumper wires. The lumbar motor should operate in the REARWARD direction.
• If the motor 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 or Passenger Seat Lumbar Control Switch Replacement Driver or Passenger Seat Lumbar Control Switch Replacement
* Seat Lumbar Sub System Replacement Seat Lumbar Sub System Replacement
* Driver or Passenger Seat Lumbar Control Switch Replacement Driver or Passenger Seat Lumbar Control Switch Replacement