Lumbar Support Inoperative With Memory A45

Battery voltage is supplied at all times to the memory seat module (MSM) from the seat interface module (SIM) and the Power Seats circuit breaker located in the I/P fuse block. This voltage is used by the MSM for logic power and 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 operated to move the lumbar support forward, battery 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 horizontal motor forward control circuit and ground through the lumbar horizontal motor rearward control circuit to the motor. The motor runs to drive the lumbar support forward toward the occupant's 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 MSM also controls the lumbar motor during memory recall functions.

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

Ignition ON, observe the scan tool MSM Lumbar Switch parameter while pressing the lumbar switch in both directions. The reading should change between Inactive and Forward or Backward.

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 12 V reference circuit terminal 3 and ground.

⇒	If the test lamp does not illuminate, test the 12 V reference circuit for an open/high resistance.

3. Verify the scan tool MSM Lumbar Switch parameter is 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 2

•	Lumbar rearward terminal 4

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

•	Lumbar forward terminal 2

•	Lumbar rearward terminal 4

⇒	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 X1 harness connector at the lumbar motor.
2. Connect a test lamp between control circuit terminal 1 and control circuit terminal 2.
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 is always 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 the 12 V reference terminal 3 and the signal terminals listed below with the switch in the open position.

•	Lumbar forward switch terminal 2

•	Lumbar rearward switch terminal 4

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

3. Test for less than 1 Ω between the 12 V reference terminal 3 and the signal terminals listed below with the appropriate switch in the closed position.

•	Lumbar forward switch terminal 2

•	Lumbar rearward switch terminal 4

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

Lumbar Motor

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

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

2. Install a 30 A fused jumper wire between control terminal 1 and 12 V. Momentarily install a jumper wire between control terminal 2 and ground. The lumbar motor should operate in the FORWARD direction.

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

3. Reverse the jumper wires. The lumbar motor should operate in the REARWARD direction.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Lumbar Support Inoperative Without Memory A45

Power seat lumbar support without memory is completely controlled through the seat adjuster switch. Battery voltage is supplied at all times to the seat switch through the SEAT 25A circuit breaker located in the I/P fuse block. When the lumbar 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

Power Seats System Description and Operation

Electrical Information Reference

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

1. Ignition OFF, disconnect the harness connector at the lumbar motor.
2. Connect a test lamp between control circuit terminal 1 and control circuit terminal 2.
3. Ignition ON, command the lumbar support FORWARD and REARWARD using the lumbar switch. The test lamp should turn ON when commanding the FORWARD and REARWARD states.

⇒	If the test lamp is always OFF during either of the commands, test for a short to ground or an open high resistance on either control circuit. If the circuits test normal, test or replace the seat adjuster switch.

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

Lumbar Switch

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

⇒	If not the specified value, replace the seat adjuster switch.

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

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

4. Test for less than 1 Ω between the ground terminal 2 and each control terminal with the switch in the open position.

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

Lumbar Motor

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

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

2. Install a 30 A fused jumper wire between control terminal 1 and 12 V. Momentarily install a jumper wire between control terminal 2 and ground. The lumbar motor should operate in the FORWARD direction.

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

3. Reverse the jumper wires. The lumbar motor should operate in the REARWARD direction.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.