Lumbar Support Inoperative (With memory A45)
Lumbar Support Inoperative (With memory A45)
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 memory seat module (MSM) from the MSM 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 LT/PWR/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.
Both lumbar motors are reversible. For example, when the lumbar switch is operated to move the lumbar support forward, battery positive 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 motor forward control circuit and ground through the lumbar motor rearward control circuit to the motor. The motor runs 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 the opposite circuits causing the motor to run in the opposite direction. The lumbar support vertical motor is also powered this way.
Reference Information
Schematic Reference
* Driver Seat Schematics Driver Seat Schematics
* Passenger Seat Schematics Passenger Seat Schematics
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
Description and Operation
Lumbar Support Description and Operation (With Memory A45) Lumbar Support (With Memory A45)Lumbar Support Description and Operation (Without Memory A45) Lumbar Support (Without Memory A45)
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 Control Module References 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 (With Memory A45) Power Seat Inoperative (With Memory A45)Power Seat Inoperative (Without Memory A45) Power Seat Inoperative (Without Memory A45).
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 adjuster 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 lumbar switch parameters are Inactive.
• If not the specified value, test the appropriate signal circuits listed below for a short to voltage. If the circuit tests normal, replace the MSM.
* Lumbar horizontal forward terminal A
* Lumbar horizontal rearward terminal F
* Lumbar vertical upward terminal C
* Lumbar vertical downward terminal B
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 A
* Lumbar horizontal rearward terminal F
* Lumbar vertical upward terminal C
* Lumbar vertical downward terminal B
• 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 X3 harness connector at the MSM.
2. Ignition ON, verify that 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.
3. Ignition OFF, connect the X3 harness connector at the MSM and disconnect the harness connector at the appropriate lumbar motor.
4. Connect a test lamp between control circuit terminal 1 and control circuit terminal 5.
5. 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.
6. If all circuits test normal, test or replace the lumbar motor.
Component Testing
Lumbar Switch
1. Ignition OFF, disconnect the harness connector at the lumbar switch.
2. Test for infinite resistance between each seat direction signal terminal listed below and the B+ terminal G with the switch in the open position.
* Lumbar vertical upward switch terminal C
* Lumbar vertical downward switch terminal B
* Lumbar horizontal forward switch terminal A
* Lumbar horizontal rearward switch terminal F
• 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 vertical upward switch terminal C
* Lumbar vertical downward switch terminal B
* Lumbar horizontal forward switch terminal A
* Lumbar horizontal rearward switch terminal F
• If greater than the specified range, replace the lumbar switch.
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
* Driver or Passenger Seat Lumbar Support Replacement Driver or Passenger Seat Lumbar Support Replacement
* Control Module References Control Module References for MSM replacement, setup, and programming