Lumbar Support Inoperative (w/o Memory A45)

Lumbar Support Inoperative (w/o Memory A45)

Circuit/System Description

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 MSM/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.


Reference Information
Schematic Reference

Driver Seat Schematics (Driver Seat Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Lumbar Support Description and Operation (w/o Memory - A45) (Lumbar Support Description and Operation (w/o Memory - A45))Lumbar Support Description and Operation (with Memory - A45) (Lumbar Support Description and Operation (with Memory - A45))
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)



Circuit/System Testing

1. Disconnect the harness connector at the lumbar adjuster switch.
2. Test for less than 1 ohm of resistance between the ground circuit terminal C and ground.

• If greater than 1 ohm, 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.
5. Disconnect the harness connector at the lumbar motor assembly.
6. Connect a test lamp between control circuit terminal 1 and control circuit terminal 2.
7. Press the lumbar switch in the Forward and Rearward directions. The test lamp should turn ON, when the switch is pressed in the Forward and Rearward directions.

• If the test lamp remains OFF 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.

8. If the circuits test normal replace the lumbar motor assembly.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Front Seat Lumbar Control Switch Replacement (Front Seat Lumbar Control Switch Replacement)