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
Power seat without memory is controlled through the seat adjuster switch. Battery voltage is supplied at all times to the seat adjuster switch through 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.
Diagnostic Aids
The seat recline motor includes an inhibit switch that is external to the motor. The purpose of the switch is to keep the internal recliner gears from being damaged when it is in operation. The inhibit switch is pigtailed off the motor and is serviced only as part of the recline motor as an assembly. The switch contacts are closed when the seat back is in the upright locked position and open when the seat back is manually dumped forward by the easy-entry mechanism. When the inhibit switch contacts are open, the seat recline function will be inoperative.
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 - Primary
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
2-Way Power Seat
Note: The seat back cushion must be in the upright locked position before performing this test. Failure to do so may result in a misdiagnosis of the recline motor.
1. Verify the M56 seat recline motor operates when pressing the seat recline switch in both directions.
• If the seat recline motor does not operate
Refer to Circuit/System Testing - Seat Recline Motor Circuit Test.
• If the seat recline motor operates
2. All OK.
8-Way Power Seat
Note: The seat back cushion must be in the upright locked position before performing this test. Failure to do so may result in a misdiagnosis of the recline motor.
1. Verify the appropriate driver or passenger seat directional motors listed below operate while pressing the seat switches in both directions.
* M51 seat horizontal motor
* M50 seat front vertical motor
* M55 seat rear vertical motor
* M56 seat recline motor
• If all seat motors do not operate
Refer to the Circuit/System Testing - Seat Adjuster Switch Circuit Test.
• If 1 or more seat motors operate but not all
Refer to Circuit/System Testing - Seat Motor Circuit Test.
• If all seat motors operate
2. All OK.
Circuit/System Testing
Seat Recline Motor Circuit Test
1. Ignition OFF, disconnect the harness connector at the appropriate S64 seat adjuster switch.
2. Test for less than 5 ohms between the ground circuit terminal B and ground.
• If 5♦ohms or greater
1. Ignition OFF.
2. Test for less than 2♦ohms in the ground circuit end to end.
• If 2♦ohms or greater, repair the open/high resistance in the circuit.
• If less than 2♦ohms, repair the open/high resistance in the ground connection.
• If less than 5♦ohms
3. Ignition ON.
4. Verify that a test lamp illuminates between the B+ circuit terminal B and ground.
• If the test lamp does not illuminate
1. Ignition OFF
2. Test for less than 2♦ohms in the B+ circuit end to end.
• If 2♦ohms or greater, repair the open/high resistance in the circuit.
• If less than 2♦ohms, verify the circuit breaker is not open and there is voltage at the circuit breaker.
• If the test lamp illuminates
5. Ignition OFF, connect the harness connector at the S64 seat adjuster switch and disconnect the harness connector at the M56 seat recline motor.
6. Connect a test lamp between control circuit terminal 1 and control circuit terminal 5, ignition ON.
7. Verify the test lamp turns illuminates when commanding the M56 seat recline motor Forward and Rearward using the seat adjuster switch.
• If the test lamp does not illuminate during either of the commands
1. Ignition OFF, disconnect the harness connector at the S64♦seat adjuster switch.
2. Test for less than 2♦ohms in each control circuit end to end.
• If 2♦ohms or greater, repair the open/high resistance in the circuit.
• If less than 2♦ohms, test or replace the S64♦seat adjuster switch
• If the test lamp illuminates during each of the commands
8. Test or replace the M56 seat recline motor.
Seat Adjuster Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the S64 seat adjuster switch.
2. Test for less than 5 ohms between the ground circuit terminal B and ground.
• If 5♦ohms or greater
1. Ignition OFF.
2. Test for less than 2♦ohms in the ground circuit end to end.
• If 2♦ohms or greater, repair the open/high resistance in the circuit.
• If less than 2♦ohms, repair the open/high resistance in the ground connection.
• If less than 5♦ohms
3. Ignition ON.
4. Verify that a test lamp illuminates between the B+ circuit terminal E and ground.
• If the test lamp does not illuminate
1. Ignition OFF
2. Test for less than 2♦ohms in the B+ circuit end to end.
• If 2♦ohms or greater, repair the open/high resistance in the circuit.
• If less than 2♦ohms, verify the circuit breaker is not open and there is voltage at the circuit breaker.
• If the test lamp illuminates
5. 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 seat horizontal motor
* 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, ignition ON.
3. Verify the test lamp illuminates when commanding the seat motor Up and Down or Forward and Rearward using the seat adjuster switch.
• If the test lamp does not illuminate during either of the commands
1. Ignition OFF, disconnect the harness connector at the S64♦seat adjuster switch.
2. Test for less than 2♦ohms in each control circuit end to end.
• If 2♦ohms or greater, repair the open/high resistance in the circuit.
• If less than 2♦ohms, test or replace the S64♦seat adjuster switch
• If the test lamp illuminates during each of the commands
4. Test or replace the seat motor.
Component Testing
Seat Adjuster Switch Test
1. Ignition OFF, disconnect the harness connector at the S64 seat adjuster switch.
2. Test for infinite resistance between the B+ terminal and each control terminal with the switch in the open position.
• If less than infinite resistance
Replace the S64 seat adjuster switch.
• If infinite resistance
3. Test for less than 2♦ohms between the B+ terminal and each control terminal with the appropriate switch in the closed position.
• If 2♦ohms or greater
Replace the S64 seat adjuster switch.
• If less than 2♦ohms
4. Test for less than 2♦ohms between the ground terminal and each control terminal with the switch in the open position.
• If 2♦ohms or greater
Replace the S64 seat adjuster switch.
• If less than 2♦ohms
5. All OK.
Seat Motor
1. Ignition OFF, disconnect the harness connector at the appropriate seat motor listed below:
* M50♦front vertical motor
* M55♦rear vertical motor
* M51♦horizontal 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.
3. 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 motor does not perform the FORWARD/ REARWARD/ UP/ DOWN function
Replace the motor.
• If the motor performs the FORWARD/ REARWARD/ UP/ DOWN function
4. Reverse the jumper wires; the motor should perform FORWARD/ REARWARD/ UP/ DOWN function.
• If the motor does not perform the FORWARD/ REARWARD/ UP/ DOWN function
Replace the motor.
• If the motor performs the FORWARD/ REARWARD/ UP/ DOWN function
5. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
Driver or Passenger Seat Adjuster Switch Replacement (with Manual Height Adjuster) Driver or Passenger Seat Adjuster Switch Replacement (with Manual Height Adjuster)Driver or Passenger Seat Adjuster Switch Replacement (with Power Height Adjuster) Driver or Passenger Seat Adjuster Switch Replacement (with Power Height Adjuster)