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
--- | --- | --- | --- | ---
Seat Adjuster Switch B+ | 1 | 1 | -- | --
Front Vertical Motor Down Control | 1 | 1 | -- | --
Front Vertical Motor Up Control | 1 | 1 | -- | --
Horizontal Motor Forward Control | 1 | 1 | -- | --
Horizontal Motor Rearward Control | 1 | 1 | -- | --
Rear Vertical Motor Down Control | 1 | 1 | -- | --
Rear Vertical Motor Up Control | 1 | 1 | -- | --
Recline Motor Forward Control | 1 | 1 | -- | --
Recline Motor Rearward Control | 1 | 1 | -- | --
Seat Adjuster Switch Ground | -- | 1 | -- | --
1. Power seat inoperative

### Circuit/System Description

Power seat without memory is completely controlled through the seat adjuster switch. Battery voltage is supplied at all times to the seat adjuster switch through the CB2 25 A circuit breaker located in the I/P fuse block. When the seat adjuster switches are in an inactive state, the switch contacts are closed to the switch ground circuit.

All seat motors are reversible. For example, when the seat horizontal forward switch is pressed to move the entire seat forward, battery voltage is applied through the switch contacts and the seat horizontal motor forward control circuit to the motor. The motor is grounded through the horizontal motor rearward switch contacts and the horizontal motor rearward control circuit to the motor. The motor runs in order to drive the entire seat forward until the switch is released. Moving the entire seat rearward works similarly to moving the entire seat forward, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction. All seat motors are powered this way.

### Reference Information

#### Schematic Reference

• | Driver Seat Schematics

• | Passenger Seat Schematics

#### Connector End View Reference

Component Connector End Views

#### 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 Verification

Operate the seat switches for the seat directional motors listed below in both directions. The seat should move in the commanded directions.

• | M51 Horizontal Motor

• | M50 Front Vertical Motor

• | M55 Rear Vertical Motor

• | M56 Recline Motor

⇒ | If the power seat is inoperative in all directions, refer to the S64 Seat Adjuster Switch Circuit Test.

⇒ | If 1 or more of the seat adjuster motors operate, refer to the Seat Adjuster Motor Circuit Test.

### Circuit/System Testing

#### S64 Seat Adjuster Switch Circuit Test

1. Disconnect the harness connector at the S64 seat adjuster switch.
2. Test for less than 5 Ω between the ground circuit terminal B and ground.

⇒ | 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 E and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, test or replace the S64 seat adjuster switch.

#### Seat Adjuster Motor Circuit Test

1. Ignition OFF, disconnect the harness connector at the appropriate seat motor listed below:

• | M51 horizontal motor

• | M50 front vertical motor

• | M55 rear vertical motor

• | M56 recline motor

2. Connect a test lamp between control circuit terminal 1 and control circuit terminal 5.
3. Ignition ON, command the appropriate seat motor Up and Down or Forward and Rearward using the seat adjuster switch. The test lamp should turn ON when commanding the up and down or 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 S64 seat adjuster switch.

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

### Component Testing

#### Seat Adjuster Switch

1. Ignition OFF, disconnect the harness connector at the S64 seat adjuster switch.
2. Test for infinite resistance between the B+ terminal E and each control terminal with the switch in the open position.

⇒ | If not the specified value, replace the S64 seat adjuster switch.

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

⇒ | If greater than the specified range, replace the S64 seat adjuster switch.

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

⇒ | If greater than the specified range, replace the S64 seat adjuster switch.

#### Seat Motor

1. Ignition OFF, disconnect the harness connector at the appropriate seat motor listed below:

• | M51 horizontal motor

• | M50 front vertical motor

• | M55 rear vertical motor

• | M56 recline motor

Note: When performing the following tests, make sure that the seat 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 5 and ground. The seat motor should momentarily perform the appropriate FORWARD/REARWARD/UP/DOWN function.

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

3. Reverse the polarity of jumper wires. The a seat motor should perform in the opposite direction.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.