Buick Regal: Power Seat Malfunction (Driver Seat with Memory A45)

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

1. All power seat motors are inoperative
2. The seat front vertical motor is inoperative
3. The seat horizontal motor is inoperative
4. The seat rear vertical motor is inoperative
5. The seat recline motor is inoperative

Circuit/System Description

Battery voltage is supplied at all times to the seat memory control module through a 5 A fuse located in the underhood fuse block. This voltage is used by the module for logic power. Battery positive voltage is also supplied at all times to the seat memory control module through a 30 A fuse also located in the underhood fuse block. This voltage is connected to a power rail internal to the seat memory control module and is used to drive all driver power seat motors. Each seat motor is controlled by the seat memory control module by applying power and ground through the control circuits to the motor.

All motors are reversible. For example, when the seat switch is operated to move the entire seat forward, the switch signal circuit from the seat memory control module is pulled low indicating the entire seat forward command. In response to this signal, the seat memory control module applies battery voltage through the driver seat horizontal motor forward control circuit and ground through the driver seat horizontal motor rearward control circuit to the motor. The motor runs 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 the opposite circuits causing the motor to run in the opposite direction. All driver power seat motors are powered this way.

Reference Information

Schematic Reference

Driver Seat Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Memory Seats Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

1. Ignition ON.

2. Verify the scan tool seat switch parameters listed below change between Inactive and Forward/Rearward or Up/Down when pressing the appropriate switch.

• Driver Seat Horizontal Switch
• Driver Seat Cushion Front Vertical Switch
• Driver Seat Cushion Rear Vertical Switch
• Driver Seat Back Switch
• If any parameter does not change

Refer to Circuit/System Testing - Seat Adjuster Switch Circuit Test

• Go to next step: If all parameters change

3. Verify the seat directional motors listed below operate when pressing the appropriate seat switches in both directions.

• M50D Seat Front Vertical Motor - Driver
• M55D Seat Rear Vertical Motor - Driver
• M51D Seat Horizontal Motor - Driver
• M56D Seat Recline Motor - Driver
• If any seat motor does not operate

Refer to Circuit/System Testing - Seat Motor Control Circuit Test.

• Go to next step: If all seat motors operate

4. All OK.

Circuit/System Testing

Seat Adjuster Switch Circuit Test

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S64D Seat Adjuster Switch - Driver. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal E and ground.

• If 10 Ω or greater

1. Ignition Off.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Install a 3 A fused jumper wire between the ground circuit terminal E and the appropriate signal circuit terminal listed below, ignition ON.

• Front vertical up switch terminal A
• Front vertical down switch terminal K
• Rear vertical up switch terminal F
• Rear vertical down switch terminal J
• Horizontal forward switch terminal D
• Horizontal rearward switch terminal C
• Recline forward switch terminal H
• Recline rearward switch terminal G

4. Verify the appropriate scan tool seat switch parameter is Forward/Rearward or UP/Down.

• If not Forward/Rearward or UP/Down

1. Ignition OFF, disconnect the X5 harness connector at the K40D Seat Memory Control Module - Driver, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Ignition OFF.
4. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40D Seat Memory Control Module - Driver.

• Go to next step: If Forward/Rearward or UP/Down

5. Test or replace the S64D Seat Adjuster Switch - Driver.

Seat Motor Control Circuit Test

1. Ignition OFF, disconnect the X2 harness connector at the K40D Seat Memory Control Module - Driver.

2. Test for less than 10 Ω between ground circuit terminal 5 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition OFF, disconnect the X1 harness connector at the K40D Seat Memory Control Module - Driver, ignition ON.

4. Verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.

• If the test lamp does not illuminate.

1. Ignition OFF, remove the test lamp.
2. Test for infinite resistance between the B+ circuit and ground.
   • If less than infinite resistance, repair the shot to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.

• Go to next step: If the test lamp illuminates.

5. Ignition OFF, connect the X1 and X2 harness connectors at the K40D Seat Memory Control Module - Driver and disconnect the harness connector at the appropriate seat motor listed below:

• M50D Seat Front Vertical Motor - Driver
• M55D Seat Rear Vertical Motor - Driver
• M51D Seat Horizontal Motor - Driver
• M56D Seat Recline Motor - Driver

6. Connect a test lamp between control circuit terminal 1 and control circuit terminal 3, ignition ON.

NOTE: Once a seat motor is commanded On using the scan tool, the seat function may not work using the seat adjuster switch until you back out of the scan tool Control Functions menu.

7. Verify the test lamp turns ON when commanding the seat motor in the Up/Down or Forward/Rearward states with a scan tool.

• If the test lamp remains OFF during either of the commands

1. Ignition OFF, disconnect the X3 harness connector at the K40D Seat Memory Control Module - Driver.
2. Test for infinite resistance between each control circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in each control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40D Seat Memory Control Module - Driver.

• Go to next step: If the test lamp turns ON during each of the commands

8. Test or replace the seat motor.

Component Testing

Seat Adjuster Switch Test

1. Ignition OFF, disconnect the harness connector at the S64D Seat Adjuster Switch - Driver.

2. Test for infinite resistance between the ground terminal E and each signal terminal with the switch in the open position.

• If less than infinite resistance

Replace the S64D Seat Adjuster Switch - Driver.

• Go to next step: If infinite resistance

3. Test for less than 2 Ω between the ground terminal E and each signal terminal with the appropriate switch in the closed position.

• If 2 Ω or greater

Replace the S64D Seat Adjuster Switch - Driver.

• Go to next step: If less than 2 Ω

4. All OK.

Seat Motor

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

• M50D Seat Front Vertical Motor - Driver
• M55D Seat Rear Vertical Motor - Driver
• M51D Seat Horizontal Motor - Driver
• M56D Seat Recline Motor - Driver

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 3 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 seat motor.

• Go to next step: 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 seat motor.

• Go to next step: If the motor performs the FORWARD/ REARWARD/ UP/ DOWN function

5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Driver or Passenger Seat Adjuster Switch Replacement
• Front Seat Tilt Adjuster Actuator Replacement
• Driver or Passenger Seat Vertical Adjuster Actuator Replacement
• Driver or Passenger Seat Recliner Actuator Replacement (Except GS) or Driver or Passenger Seat Recliner Actuator Replacement (GS)
• Control Module References for K40D Seat Memory Control Module - Driver replacement, programming and setup

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