Lumbar Support Inoperative Without Memory A45

Power seat lumbar support without memory is completely controlled through the seat lumbar adjuster switch. Battery voltage is supplied at all times to the lumbar switches from the PWR SEAT 25A circuit breaker for the driver seat and the RF SEAT 25A circuit breaker for the passenger seat that are located in the rear fuse block. Battery voltage is supplied at all times to both rear passenger seat lumbar switches from the SWS RR 20A fuse also located in the rear fuse block. When the seat adjuster switches are in an inactive state, the switch contacts are closed to the switch ground circuit.

Both lumbar motors are 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. The lumbar support vertical motor is also powered this way.

Schematic Reference

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 appropriate lumbar switch.
2. Test for less than 1 ohm between the appropriate ground circuit listed below and ground:

•	Front seat lumbar switch terminal E

•	Rear seat lumbar switch terminal 5

⇒	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 appropriate B+ circuit listed below and ground:

•	Front seat lumbar switch terminal G

•	Rear seat lumbar switch terminal 7

⇒	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 appropriate lumbar motor.
5. Connect a test lamp between control circuit terminal A and control circuit terminal B.
6. Ignition ON, command the lumbar motor Forward and Rearward or Up and Down using the seat lumbar switch. The test lamp should turn ON when commanding the forward and rearward or up and down states.

⇒	If the test lamp remains OFF for 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 switch.

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

Lumbar Switch

1. Ignition OFF, disconnect the harness connector at the lumbar switch.
2. Test for infinite resistance between the B+ terminal G and the switch terminals listed below 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 the B+ terminal G and the switch terminals listed below with the appropriate 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.

4. Test for less than 1 ohm between the ground terminal E and the switch terminals listed below 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 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 MDL-MEM 10A fuse located in the rear 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 supplied at all times to the MSM from the PWR SEAT 25A circuit breaker located in the I/P fuse block. This voltage is connected to power rail 1 internal to the MSM and is used to drive the driver seat adjuster motors, recline motor, and the lumbar horizontal motor. Battery positive voltage is also supplied at all times to the MSM from the PWR T/T 25A circuit breaker also located in the rear fuse block. This voltage is connected to power rail 2 and is used to drive the driver seat lumbar vertical motor, passenger seat lumbar vertical motor, and the tilt and telescoping steering column actuators. 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.

All 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 scan tool may reference the Memory Seat Module as the Driver Position Module.

Schematic Reference

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 are inoperative, refer to Lumbar Support Inoperative.

2. Observe the scan tool Driver Position Module lumbar switch parameters for Seat 1 and Seat 2 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 appropriate 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 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 B+ circuit terminal G and appropriate signal circuit listed below. Verify the appropriate scan tool lumbar witch 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 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. Verify that a test lamp illuminates between the B+ circuit terminal 5 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 X3 harness connector at the MSM and disconnect the harness connector at the appropriate lumbar motor.
5. Connect a test lamp between control circuit terminal A and control circuit terminal B.
6. 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.

7. 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 the B+ terminal G and the switch terminals listed below with the switch in the open position:

•	Lumbar horizontal forward switch terminal C

•	Lumbar horizontal rearward switch terminal B

•	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 the B+ terminal G and the switch terminals listed below with the switch in the closed position:

•	Lumbar horizontal forward switch terminal C

•	Lumbar horizontal rearward switch terminal B

•	Lumbar vertical upward switch terminal F

•	Lumbar vertical downward switch terminal A

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.