GM Service Manual Online
For 1990-2009 cars only

Power Seat Inoperative Without 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

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Seat Adjuster Switch B+

1

1

--

--

Front Vertical Motor Down Control

3

3

--

--

Front Vertical Motor Up Control

3

3

--

--

Horizontal Motor Forward Control

2

2

--

--

Horizontal Motor Rearward Control

2

2

--

--

Rear Vertical Motor Down Control

4

4

--

--

Rear Vertical Motor Up Control

4

4

--

--

Seat Adjuster Switch Ground

--

1

--

--

1. Power seat inoperative

2. Seat horizontal motor is inoperative

3. Seat front vertical motor is inoperative

4. Seat rear vertical motor is inoperative

Circuit/System Description

Battery voltage is supplied at all times to the driver and passenger seat adjuster switches through the PWR SEATS MSM 30 A circuit breaker located in the I/P fuse block. When a seat adjuster switch is in an inactive state, the switch contacts are closed to the switch ground circuit.

All power seat adjuster 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 operate 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 adjuster switches for the seat directional motors listed below in both directions. The seat should move in the commanded directions.

    • Seat horizontal motor
    • Seat front vertical motor
    • Seat rear vertical motor
If all power seat functions are inoperative, refer to the Seat Adjuster Switch Circuit Test.
If one 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 seat adjuster switch.
  2. Test for less than 1 Ω between the ground circuit terminal H and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
    Ignition ON, 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 seat adjuster switch.

Seat Adjuster Motor Circuit Test

  1. Ignition OFF, disconnect the harness connector at the seat adjuster motor assembly.
  2. Connect a test lamp between the appropriate control circuits listed below:
  3. • Seat horizontal motor terminal A and terminal B
    • Seat front vertical motor terminal C and terminal D
    • Seat rear vertical motor terminal E and terminal F
  4. 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.
  5. 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 seat adjuster switch.
  6. If all circuits test normal, replace the seat adjuster motor assembly.

Component Testing

Seat Adjuster Switch

  1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
  2. Test for infinite resistance between the B+ terminal E and the switch terminals listed below with the switch in the open position:
  3. • Front vertical upward switch terminal B
    • Front vertical downward switch terminal D
    • Rear vertical upward switch terminal A
    • Rear vertical downward switch terminal G
    • Horizontal forward switch terminal C
    • Horizontal rearward switch terminal F
    If not the specified value, replace the seat adjuster switch.
  4. Test for less than 1 Ω between the B+ terminal E and the switch terminals listed below with the appropriate switch in the closed position:
  5. • Front vertical upward switch terminal B
    • Front vertical downward switch terminal D
    • Rear vertical upward switch terminal A
    • Rear vertical downward switch terminal G
    • Horizontal forward switch terminal C
    • Horizontal rearward switch terminal F
    If greater than the specified range, replace the seat adjuster switch.
  6. Test for less than 1 Ω between the ground terminal H and the switch terminals listed below with the switch in the open position.
  7. • Front vertical upward switch terminal B
    • Front vertical downward switch terminal D
    • Rear vertical upward switch terminal A
    • Rear vertical downward switch terminal G
    • Horizontal forward switch terminal C
    • Horizontal rearward switch terminal F
    If greater than the specified range, replace the seat adjuster switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Seat Adjuster Motor Replacement
    •  Power Seat Switch Replacement

Power Seat Inoperative 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

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Memory Seat Module B+ Terminal B11 X2

B1420

B1420

--

--

Memory Seat Module B+ Terminal A X1

2

2

--

--

Seat Adjuster Switch B+

B1420

1

--

--

Power Seat Front Vertical Up Switch Signal

B1420

1

B1735, B1740, B1745, B1750, B1755, B1760

--

Power Seat Front Vertical Down Switch Signal

B1420

1

B1735, B1740, B1745, B1750, B1755, B1760

--

Power Seat Horizontal Rearward Switch Signal

B1420

1

B1735, B1740, B1745, B1750, B1755, B1760

--

Power Seat Horizontal Forward Switch Signal

B1420

1

B1735, B1740, B1745, B1750, B1755, B1760

--

Power Seat Rear Vertical Up Switch Signal

B1420

1

B1735, B1740, B1745, B1750, B1755, B1760

--

Power Seat Rear Vertical Down Switch Signal

B1420

1

B1735, B1740, B1745, B1750, B1755, B1760

--

Driver Seat Front Vertical Motor Down Control

B1336

1

--

--

Driver Seat Front Vertical Motor Up Control

B1336

1

--

--

Driver Seat Rear Vertical Motor Down Control

B1336

1

--

--

Driver Seat Rear Vertical Motor Up Control

B1336

1

--

--

Driver Seat Horizontal Motor Forward Control

B1336

1

--

--

Driver Seat Horizontal Motor Rearward Control

B1336

1

--

--

Memory Seat Module Ground

--

2

--

--

  1. The power seat is inoperative
  2. The scan tool does not communicate with the memory seat module

Circuit/System Description

Battery positive voltage is supplied at all times to the seat adjuster switch, memory seat adjuster switch, and memory seat module (MSM) from the TILT/TELE SW/MEM SEAT MOD 10A fuse located in the Body Control Module (BCM) fuse block. When a seat adjustment switch is pressed, battery voltage is applied through the switch contacts and the appropriate switch signal circuit to the MSM. The MSM then commands the selected seat motor to move in response to the switch signal.

All motors are reversible. For example, when the seat switch is operated to moved the entire seat forward, battery positive voltage is applied through the horizontal forward switch contacts and the power seat horizontal forward switch signal circuit to the MSM. In response to this signal, the MSM applies battery positive voltage through the driver seat horizontal motor forward control circuit to the horizontal motor. The MSM supplies ground to the motor through the driver seat horizontal motor rearward control circuit. 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 other seat motors are also powered this way.

Diagnostic Aids

The memory seat module is also referred to as the Driver Position Module in certain scan tool menus.

Reference Information

Schematic Reference

Driver 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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Ignition ON, observe the scan tool Driver Position Module seat switch parameters while pressing the appropriate seat switch. The reading should change between Inactive and Active.
  2. If the reading does not change between the specified values, refer to the Seat Adjuster Switch Circuit Test.
  3. If all seat switch inputs to the MSM function normal, refer to the Seat Motor Control Circuit Test

Circuit/System Testing

Seat Adjuster Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the driver seat adjuster switch.
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal E and ground.
  3. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify all scan tool Driver Position Module power seat switch parameters are Inactive.
  5. If not the specified value, test the appropriate signal circuit listed below for a short to voltage. If the circuit tests normal, replace the MSM.
    • Front vertical up switch terminal B
    • Front vertical down switch terminal D
    • Horizontal forward switch terminal C
    • Horizontal rearward switch terminal F
    • Rear vertical up switch terminal A
    • Rear vertical down switch terminal G
  6. Install a 3 A fused jumper wire between the B+ circuit terminal E and the appropriate switch signal circuit terminal listed below. Verify the appropriate scan tool seat switch parameter is Active.
  7. • Front vertical up switch terminal B
    • Front vertical down switch terminal D
    • Horizontal forward switch terminal C
    • Horizontal rearward switch terminal F
    • Rear vertical up switch terminal A
    • Rear vertical down switch terminal G
    If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
  8. If all circuits test normal, test or replace the driver seat adjuster switch.

Seat Adjuster Motor Circuit Test

  1. Ignition OFF, disconnect the X1 harness connector at the seat adjuster motor assembly.
  2. Connect a test lamp between the appropriate control circuit terminals listed below:
  3. • Seat horizontal motor terminal A and terminal  B
    • Seat front vertical motor terminal C and terminal D
    • Seat rear vertical motor terminal E and terminal F
  4. Ignition ON, command the appropriate seat motor in the Up/Down or Forward/Rearward directions with a scan tool. The test lamp should turn ON when commanding the up and down or forward and rearward states.
  5. If the test lamp remains OFF during either of the commands, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal, replace the MSM.
  6. If all circuits test normal, test or replace the seat adjuster motor.

Component Testing

Seat Adjuster Switch

  1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
  2. Test for infinite resistance between the B+ terminal E and the switch terminals listed below with the switch in the open position.
  3. • Front vertical up switch terminal B
    • Front vertical down switch terminal D
    • Horizontal forward switch terminal C
    • Horizontal rearward switch terminal F
    • Rear vertical up switch terminal A
    • Rear vertical down switch terminal G
    If not the specified value, replace the seat adjuster switch.
  4. Test for less than 1 Ω between the B+ terminal E and the switch terminals listed below with the appropriate switch in the closed position.
  5. • Front vertical up switch terminal B
    • Front vertical down switch terminal D
    • Horizontal forward switch terminal C
    • Horizontal rearward switch terminal F
    • Rear vertical up switch terminal A
    • Rear vertical down switch terminal G
    If greater than the specified range, replace the seat adjuster switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Seat Adjuster Motor Replacement
    •  Power Seat Switch Replacement
    •  Control Module References for MSM replacement, setup, and programming