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 Instructionsprovides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
Battery voltage is supplied at all times to the memory seat module (MSM) from the DSM 10A fuse located in the I/P fuse block. This voltage is used by the MSM for logic power and to supply battery reference voltage to the seat and lumbar adjuster switches. Battery positive voltage is also supplied at all times to the MSM from the DRIVER SEAT 25A circuit breaker also located in the I/P fuse block. This voltage is connected to a power rail internal to the MSM and is used to drive the power seat motors, lumbar motors, and seat heater elements on vehicles equipped with heated seats. Each seat and lumbar adjuster motor is controlled by the MSM through 2 motor control circuits. The MSM connects all motor control circuits on the power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.5 volts. The MSM checks to see if the reference voltage is shorted to ground or battery before enabling any of the seat or lumbar motors.
The lumbar motors are reversible. For example, when the lumbar switch is operated to move the lumbar horizontal forward, battery voltage is applied through the switch contacts and the lumbar horizontal forward switch signal circuit to the MSM. In response to this signal, the MSM applies battery voltage through the lumbar horizontal motor forward control circuit and ground through the lumbar horizontal motor rearward control circuit to the motor. The motor runs to drive the lumbar support forward toward the occupant's 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 the opposite circuits causing the motor to run in the opposite direction. The MSM also controls the lumbar horizontal motor during memory recall functions.
Reference Information
Schematic Reference
Driver Seat Schematics Driver Seat Schematics
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Memory Seats Description and Operation Memory Seats
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
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information
Circuit/System Verification
1. Ignition ON, verify that all manual power seat functions operate when being controlled by the seat adjuster switches.
• If all seat functions do not operate, refer to Power Seat Inoperative .
2. Ignition ON, observe the scan tool Memory Seat Module Lumbar Switch parameters while pressing the appropriate lumbar switch. The reading should change between Inactive and Active.
• If the reading does not change between the specified values, refer to the Lumbar Switch Circuit Test.
3. If all lumbar switch inputs to the MSM function normal, refer to the Lumbar Motor Control Circuit Test.
Circuit/System Testing
Lumbar Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the lumbar switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal G and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
3. Verify that all scan tool Memory Seat Module lumbar switch parameters are Inactive.
• If not the specified value, test the appropriate signal circuit listed below for a short to voltage. If the circuit tests normal, replace the MSM.
* Lumbar horizontal forward terminal C
* Lumbar horizontal rearward terminal B
* Lumbar vertical upward terminal F
* Lumbar vertical downward terminal A
4. Install a 3A fused jumper wire between the appropriate signal circuit listed below and the B+ circuit terminal G. Verify the scan tool Lumbar Switch parameter is Active.
* Lumbar horizontal forward terminal C
* Lumbar horizontal rearward terminal B
* Lumbar vertical upward terminal F
* Lumbar vertical downward terminal A
• If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
5. If all circuits test normal, test or replace the lumbar switch.
Lumbar Motor Control Circuit Test
1. Ignition OFF, disconnect the X1 harness connector at the lumbar adjuster motor assembly.
2. Connect a test lamp between the appropriate control circuits listed below:
* Lumbar horizontal motor terminal C and terminal D
* Lumbar vertical motor terminal A and terminal B
3. Ignition ON, command the appropriate lumbar motor in the Up/Down or Forward/Rearward directions with a scan tool. The test lamp should turn ON when commanding the up and down or forward and rearward states.
• If the test lamp remains OFF during either of the commands, test the control circuits for an open/high resistance. If the circuits test normal replace the MSM.
4. If all circuits test normal, test or replace the lumbar adjuster assembly.
Component Testing
Lumbar Switch
1. Ignition OFF, disconnect the harness connector at the lumbar switch.
2. Test for infinite resistance between each lumbar direction signal terminal listed below and the B+ terminal G with the switch in the open position.
* Lumbar horizontal forward switch terminal B
* Lumbar horizontal rearward switch terminal C
* Lumbar vertical upward switch terminal F
* Lumbar vertical downward switch terminal A
• If not the specified value, replace the lumbar switch.
3. Test for less than 1 ohm between each lumbar direction signal terminal listed below and the B+ terminal G with the switch in the closed position.
* Lumbar horizontal forward switch terminal B
* Lumbar horizontal rearward switch terminal C
* Lumbar vertical upward switch terminal F
* Lumbar vertical downward switch terminal A
• If greater than the specified range, replace the lumbar switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Lumbar Switch Replacement Lumbar Switch Replacement
* Seat Lumbar Sub System Replacement Seat Lumbar Sub System Replacement
* Control Module References Programming and Relearningfor MSM replacement, setup, and programming