Lumbar Support Inoperative Without Memory A45

Power seat lumbar support without memory is completely controlled through the lumbar switch. Battery voltage is supplied at all times to the lumbar switch from the 30 A SEATS circuit breaker that is 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 at G303.

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.

Schematic Reference

Passenger Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Lumbar Support Description and Operation

Electrical Information Reference

1. Ignition OFF, disconnect the harness connector at the lumbar adjuster switch.
2. Test for less than 1 ohm between the appropriate ground circuit terminal listed below and ground:

•	Driver seat lumbar switch terminal H

•	Passenger seat lumbar switch terminal E

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the appropriate B+ circuit terminal listed below and ground:

•	Driver seat lumbar switch terminal E

•	Passenger seat lumbar switch terminal G

⇒	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 lumbar switch and disconnect the harness connector at the lumbar motor.
5. Connect a test lamp between control circuit terminal A and control circuit terminal B.
6. Operate the lumbar switch in both directions. The test lamp should turn ON when commanding the lumbar motor in both directions.

⇒	If the test lamp remains 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 lumbar adjuster switch.

7. If all circuits test normal, test or replace the lumbar motor.

Lumbar Adjuster Switch

1. Ignition OFF, disconnect the harness connector at the lumbar adjuster switch.
2. Test for infinite resistance between each control terminal and the B+ terminal with the switch in the open position.

⇒	If not the specified value, replace the lumbar switch.

3. Test for less than 1 ohm between each control terminal and the B+ terminal with the switch in the closed position.

⇒	If greater than the specified range, replace the lumbar switch.

4. Test for less than 1 ohm between each control terminal and the ground terminal with the switch in the open position.

⇒	If greater than the specified range, replace the lumbar switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Lumbar Support Inoperative With Memory A45

Battery voltage is supplied at all times to the memory seat module (MSM) from the 10A LGM/DSM fuse located in the rear fuse block. This voltage is used by the MSM for logic power and to supply battery voltage to the seat and lumbar switches. Battery voltage is supplied at all times to the MSM from the SEATS 30A circuit breaker also located in the rear fuse block. This voltage is used by the MSM to drive the driver seat adjuster motors, recline motor and the lumbar motor.

The lumbar motor is reversible. For example, when the lumbar switch is pressed to move the lumbar support forward, battery positive voltage is applied through the switch contacts and the lumbar 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 scan tool may reference the Memory Seat Module (MSM) as the Driver Seat Module.

Schematic Reference

Driver Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Lumbar Support Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, verify that all manual power seat functions operate when being controlled by the seat adjuster switches.

⇒	If all power seat functions do not operate, refer to Power Seat Inoperative.

2. Ignition ON, observe the scan tool Driver Seat Module lumbar switch parameter while pressing the lumbar switch. The reading should change between Idle, Forward and Rearward.

⇒	If the reading does not change between the specified values, refer to the Lumbar Switch Circuit Test.

3. If the lumbar switch inputs to the MSM function normal, refer to the Lumbar Motor Control Circuit Test.

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 E 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 the scan tool Lumbar Switches parameter is Idle.

⇒	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

4. Install a 3A fused jumper wire between the B+ circuit terminal E and the appropriate signal circuit listed below. Verify the scan tool Lumbar Switch parameter is Forward or Rearward.

•	Lumbar horizontal forward terminal C

•	Lumbar horizontal rearward 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 adjuster switch.

Lumbar Motor Control Circuit Test

1. Ignition OFF, disconnect the harness connector at the lumbar motor.
2. Connect a test lamp between control circuit terminal A and control circuit terminal B.
3. Ignition ON, command the lumbar motor in the Froward/Rearward directions with a scan tool. The test lamp should turn ON when commanding the froward and rearward states.

⇒	If the test lamp remains 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 replace the MSM.

4. If all circuits test normal, test or replace the lumbar motor.

Lumbar Switch

1. Ignition OFF, disconnect the harness connector at the lumbar adjuster switch.
2. Test for infinite resistance between the B+ terminal E and each seat direction signal terminal listed below with the switch in the open position.

•	Lumbar horizontal forward switch terminal A

•	Lumbar horizontal rearward switch terminal D

⇒	If not the specified value, replace the lumbar switch.

3. Test for infinite resistance between the B+ terminal E and each seat direction signal terminal listed below with the switch in the closed position.

•	Lumbar horizontal forward switch terminal A

•	Lumbar horizontal rearward switch terminal D

⇒	If greater than the specified range, replace the lumbar switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.