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 seat lumbar adjuster switch from the RT/FRT/PWR/SEAT 25A circuit breaker that is located in the rear fuse block. When the seat lumbar adjuster switches are in an inactive state, the switch contacts are closed to the switch ground circuit.

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. Disconnect the harness connector at the lumbar adjuster switch.
2. Test for less than 1 ohm of resistance 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. 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. Connect the harness connector at the lumbar adjuster switch and disconnect the harness connector at the lumbar motor.
5. Ignition ON, verify that a test lamp illuminates between control circuit terminal 1 and control circuit terminal 2 while pressing the lumbar switch in both directions.

⇒	If the test lamp does not illuminate for either direction, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal replace the lumbar adjuster switch.

6. If the 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 control 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 control 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 control 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.

Lumbar Motor

1. Ignition OFF, disconnect the harness connector at the lumbar motor.

Important: When performing the following tests, make sure that the lumbar support is not already in the position the test is attempting to produce.

2. Install a 30A fused jumper wire between the control terminal 1 and 12 volts. Momentarily install a jumper wire between the control terminal 2 and ground. The lumbar motor should momentarily perform the FORWARD function.

⇒	If the function does not perform as specified, replace the lumbar motor.

3. Reverse the polarity of jumper wires; the a lumbar motor should perform REARWARD function.

⇒	If the function does not perform as specified, replace the lumbar motor.

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 MSM fuse. 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 LF/FRT/PWR/SEAT 25A circuit breaker. 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 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

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 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 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 Adjuster 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 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 the 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 forward terminal B

•	Lumbar rearward terminal E

4. Install a 3A fused jumper wire between the appropriate signal circuit listed below and the B+ circuit terminal D. Verify the scan tool lumbar switch parameter is Active.

•	Lumbar forward terminal B

•	Lumbar rearward terminal E

⇒	If not specified value, test the signal circuit for 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 forward and rearward directions with a scan tool. The test lamp should turn ON when commanding the forward and rearward states.

⇒	If the test lamp remains OFF during either of the commands, test the motor 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 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 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.

Lumbar Motor

1. Ignition OFF, disconnect the harness connector at the appropriate lumbar motor.

Important: When performing the following tests, make sure that the lumbar support is not already in the position the test is attempting to produce.

2. Install a 30A fused jumper wire between the control terminal A and 12 volts. Momentarily install a jumper wire between the control terminal B and ground. The lumbar motor should momentarily perform the FORWARD function.

⇒	If the function does not perform as specified, replace the lumbar motor.

3. Reverse the polarity of jumper wires; the a lumbar motor should perform REARWARD function.

⇒	If the function does not perform as specified, replace the lumbar motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.