For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+, Lumbar Adjuster Switch | 1, 2 | 2 | -- | --
Lumbar Horizontal Motor Rearward Control | 2 | 2 | -- | --
Lumbar Horizontal Motor Forward Control | 2 | 2 | -- | --
Ground - Lumbar Adjuster Switch | -- | 2 | -- | --

1. Power seats inoperative
2. Lumbar support inoperative

### Circuit/System Description

The power lumbar system is controlled through the lumbar adjuster switch. Battery voltage is supplied to the lumbar adjuster switches through the PWR/SEAT 40A fuse for the driver seat and the HTD/SEAT 20A fuse for the passenger seat that are located in the underhood fuse block. While the lumbar switch is in an inactive state the switch contacts are closed to the lumbar 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

• | Passenger Seat Schematics

#### Connector End View Reference

Lumbar Support Description and Operation

#### Description and Operation

Power Seats System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the lumbar adjuster switch.
2. Test for less than 5 ohms between the ground circuit terminal A and ground.

⇒ | 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 B+ circuit terminal H 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 harness connector at the lumbar adjuster switch and disconnect the harness connector at the lumbar motor.
5. Connect a test lamp between control terminal A and control circuit terminal B.
6. Ignition ON, command the lumbar motor Forward and Rearward using the lumbar adjuster switch. The test lamp should turn ON when commanding the forward and rearward 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 replace the lumbar motor.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the lumbar adjuster switch.
2. Test for infinite resistance between the B+ terminal H and the switch terminals listed below with the switch in the open position:

• | Lumbar horizontal forward switch terminal F

• | Lumbar horizontal rearward switch terminal G

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

3. Test for less than 1 ohm between the B+ terminal H and the switch terminals listed below with the appropriate switch in the closed position:

• | Lumbar horizontal forward switch terminal F

• | Lumbar horizontal rearward switch terminal G

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

4. Test for less than 1 ohm between the ground terminal A and the switch terminals listed below with the switch in the open position.

• | Lumbar horizontal forward switch terminal F

• | Lumbar horizontal rearward switch terminal G

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Lumbar Switch Replacement

• | Front Seat Lumbar Support Replacement