Lumbar Support Inoperative Without Memory - A45

Power seat lumbar support without memory is completely controlled through the seat lumbar switch. Battery voltage is supplied at all times to the lumbar switch from the PWR SEAT 30A circuit breaker that is located in the right rear fuse block. When the lumbar switches are in an inactive state, the switch contacts are closed to the switch ground circuit.

The lumbar horizontal 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

Connector End View Reference

Component Connector End Views

Description and Operation

Power Seats System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References

1. Ignition OFF, disconnect the harness connector at the lumbar switch.
2. Ignition OFF, test for less than 5 ohms between the ground circuits 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 lumbar switch and disconnect the harness connector at the lumbar 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 both directions, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal, test or replace the lumbar switch.

6. If all circuits test normal, replace the lumbar motor.

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 D 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 lumbar switch.

3. Test for less than 1 ohm between each lumbar direction signal terminal listed below and the B+ terminal D with the 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 lumbar switch.

4. Test for less than 1 ohm between each lumbar direction signal 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 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 MEMORY RPA 7.5A fuse located in the left rear fuse block. This voltage is used by the MSM for logic power and to supply reference voltage to the seat and lumbar adjuster switches. Battery positive voltage is also supplied at all times to the MSM from the PWR SEATS 30A circuit breaker located in the right rear fuse block. This voltage is connected to a power rail internal to the MSM and is used to drive the power seat motors, lumbar motor, adjustable pedal motor, and the 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 horizontal motor is 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.

Schematic Reference

Driver Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Seats System 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 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.

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 D 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 B

•	Lumbar horizontal rearward terminal E

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 B

•	Lumbar horizontal rearward terminal E

⇒	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 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 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 switch.
2. Test for infinite resistance between each lumbar direction signal terminal listed below and the B+ terminal D 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 lumbar switch.

3. Test for less than 1 ohm between each lumbar direction signal terminal listed below and the B+ terminal D with the 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 lumbar switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.