Lumbar Support Inoperative w/o 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 PWR SEAT 30A circuit breaker that is located in the right rear fuse block. When the seat adjuster 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

Power Seat Connector End Views

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 circuit terminals A and C and ground.

⇒	If greater than 1 ohm, 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. Connect the harness connector at the lumbar adjuster switch.
5. Disconnect the harness connector at the lumbar motor.
6. Connect a test lamp between the motor control circuits terminal A and terminal B.
7. Press the lumbar switch in the FORWARD and REARWARD directions. The test lamp should turn ON while pressing the switch in the both directions.

⇒	If the test lamp remains OFF for either direction, test the motor circuits for a short to ground or an open/high resistance. If the circuits test normal, test or replace the lumbar adjuster switch.

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

Lumbar Switch

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

⇒	If less than the specified value, replace the lumbar adjuster switch.

3. Test for less than 1 ohm of resistance between each control terminal (B and E) and the B+ terminal D with the switch in the closed position.

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

4. Test for less than 1 ohm of resistance between the control terminal B and the ground terminal C with the switch in the open position.

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

5. Test for less than 1 ohm of resistance between the control terminal E and the ground terminal A with the switch in the open position.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Lumbar Support Inoperative with Memory-A45

A low current battery voltage is supplied at all times to the memory seat module (MSM) from the 7.5A MEMORY RPA fuse located in the left 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 also supplied at all times to the MSM from the PWR SEATS 30A circuit breaker located in the left 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

Power Seat Connector End Views

Electrical Information Reference

Scan Tool Reference

1. Ignition ON, verify the scan tool Lumbar Switch parameters are Active while pressing the lumbar switch in both directions.

⇒	If not the specified value for both directions, perform the Lumbar Switch Circuit/System Test.

2. Verify the scan tool Lumbar Switch parameters are Inactive while the switch is in an inactive state.

⇒	If not the specified value, perform the Lumbar Switch Circuit/System Test.

3. If both lumbar switch inputs to the MSM function normal, preform the Motor Circuit/System Test.

Lumbar Adjuster Switch Circuit/System Test

1. Ignition OFF, disconnect the harness connector at the lumbar adjuster switch.
2. Ignition ON, verify the following scan tool parameters are Inactive:

•	Lumbar Forward Switch

•	Lumbar Rearward Switch

⇒	If not the specified value, test the signal circuit terminals E and B for a short to voltage. If the circuits test normal, replace the MSM.

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. If the circuit tests normal, replace the MSM.

4. Install a 3A fused jumper wire between the inoperative switch signal circuit terminal B or E and the B+ circuit terminal D. Verify the related scan tool Lumbar Switch parameter is Active.

⇒	If not the 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.

Motor Circuit/System Test

1. Disconnect the (C3) harness connector at the MSM.
2. 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.

3. Connect the (C3) harness connector at the MSM.
4. Disconnect the (C1) harness connector at the seat lumbar motor.
5. Connect a test lamp between the motor control circuits terminal A and terminal B.
6. The test lamp should illuminate while pressing the switch in both directions.

⇒	If the test lamp does not illuminate, test the motor control circuits for an open/high resistance. If the circuits test normal replace the MSM.

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

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

⇒	If less than the specified value, replace the lumbar adjuster switch.

3. Test for less than 1 ohm of resistance between each signal terminal B and E and the B+ terminal D with the related switch in the closed position.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.