Power Seat Malfunction
Power Seat Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The power seat is controlled through the seat adjuster switch. Battery voltage is supplied at all times to the seat adjuster switch through a 20 A circuit breaker located in the instrument panel 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 recline forward switch is pressed to move the seat back support forward, battery voltage is applied through the switch contacts and the seat recline motor forward control circuit to the motor. The motor is grounded through the recline motor rearward switch contacts and the recline motor rearward control circuit to the motor. The motor runs in order to drive the seat back support forward until the switch is released. Moving the seat back support rearward works similarly to moving the seat back 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 Driver Seat Schematics
* Passenger Seat Schematics Passenger Seat Schematics
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Power Seats System Description and Operation Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Circuit/System Verification
Operate the seat switches for the appropriate seat directional motors listed below in both directions. The seat should move in the commanded directions.
* M50 Front Vertical Motor
* M55 Rear Vertical Motor
* M56 Recline Motor
If the power seat is inoperative in all directions, refer to the 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
Seat Adjuster Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the appropriate S64 Seat Adjuster Switch.
2. Test for less than 5 omhs between the ground circuit terminal 5 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 1 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:
* M50 Seat Front Vertical Motor
* M55 Seat Rear Vertical Motor
* M56 Seat Recline Motor
2. Connect a test lamp between control circuit terminal 1 and control circuit terminal 5.
3. Ignition ON, command the 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 tests normal, test or replace the seat motor.
Component Testing
Seat Adjuster Switch Test
1. Ignition OFF, disconnect the harness connector at the appropriate S64 Seat Adjuster Switch.
2. Test for infinite resistance between the B+ terminal 1 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 omhs 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 S64 Seat Adjuster Switch.
4. Test for less than 1 omhs between the ground terminal 5 and each control terminal with the switch in the open position.
• If greater than the specified range, replace the S64 Seat Adjuster Switch.
Seat Motors
1. Ignition OFF, disconnect the harness connector at the appropriate seat motor listed below:
* M50 Seat Front Vertical Motor
* M55 Seat Rear Vertical Motor
* M56 Seat 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 operate in the appropriate UP or FORWARD direction.
• If the motor does not perform as specified, replace the seat motor.
3. Reverse the jumper wires. The seat motor should operate in the appropriate DOWN or REARWARD direction.
• If the motor does not perform as specified, replace the seat motor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Power Seat Switch Replacement (Right Seat) Power Seat Switch Replacement (Right Seat)Power Seat Switch Replacement (Left Seat) Power Seat Switch Replacement (Left Seat)
* Front Seat Adjuster Replacement Front Seat Adjuster Replacement