For 1990-2009 cars

## Power Seat Malfunction 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 1 X4 | 2 | 2 | -- | --
Memory Seat Module B+ Terminal 5 X4 | B2425 0D, B2430 0D, 1, 3 | B2425 0D, B2430 0D, 1, 3 | -- | --
Front Vertical Up Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Front Vertical Down Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Rear Vertical Up Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Rear Vertical Down Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Horizontal Forward Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Horizontal Rearward Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Recline Forward Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Recline Rearward Switch Signal | B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02 | 1 | -- | --
Driver Seat Front Vertical Motor Down Control | B3920 02 | 1 | B3920 01 | B3920 00
Driver Seat Front Vertical Motor Up Control | B3920 02 | 1 | B3920 01 | B3920 00
Driver Seat Horizontal Motor Forward Control | B3920 02 | 1 | B3920 01 | B3920 00
Driver Seat Horizontal Motor Rearward Control | B3920 02 | 1 | B3920 01 | B3920 00
Driver Seat Rear Vertical Motor Down Control | B3920 02 | 1 | B3920 01 | B3920 00
Driver Seat Rear Vertical Motor Up Control | B3920 02 | 1 | B3920 01 | B3920 00
Driver Seat Recline Motor Forward Control | B3920 02 | 1 | B3920 01 | B3920 00
Driver Seat Recline Motor Rearward Control | B3920 02 | 1 | B3920 01 | B3920 00
Ground - K40 Memory Seat Module Terminal 3 X4 | -- | -- | -- | --
Ground - K40 Memory Seat Module Terminal 6 X4 | -- | -- | -- | --
Ground - Splice J354 | -- | 2 | -- | --
1. Power seat and memory functions inoperative 2. Scan Tool Does Not Communicate with Low Speed GMLAN Device 3. Heated seats are inoperative

### Circuit/System Description

Battery voltage is supplied at all times to the memory seat module from the F19DA 5 A fuse located in the I/P fuse block. This voltage is used by the memory seat module for logic power. Battery positive voltage is also supplied at all times to the memory seat module from the F13DA 25A fuse. This voltage is connected to a power rail internal to the memory seat module and is used to drive the power seat motors, lumbar motors, and seat heater elements on vehicles equipped with heated seats. Each seat and lumbar adjuster motor is controlled by the memory seat module through 2 motor control circuits. The memory seat module connects all motor control circuits on the power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.5 volts. The memory seat module checks to see if the reference voltage is shorted to ground or battery before enabling any of the seat motors.

All motors are reversible. For example, when the seat switch is operated to move the entire seat forward, battery positive voltage is applied through the switch contacts and the power seat horizontal forward switch signal circuit to the memory seat module. In response to this signal, the memory seat 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.

### Reference Information

#### Schematic Reference

Driver Seat Schematics

#### Connector End View Reference

Component Connector End Views

#### 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, observe the scan tool K40 Memory Seat Module seat switch parameters listed below while pressing the appropriate seat adjuster switch. The reading should change between Inactive and Forward/Rearward or Up/Down.

• | Driver Seat Horizontal Switch

• | Driver Seat Cushion Front Vertical Switch

• | Driver Seat Cushion Rear Vertical Switch

• | Driver Seat Back Switch

⇒ | If the reading does not change between the specified values, refer to the Seat Adjuster Switch Circuit Test.

2. If all seat switch inputs to the K40 memory seat module 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 S64D seat adjuster switch.
2. Test for less than 1 Ω between the ground circuit terminal E and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that the scan tool K40 Memory Seat Module seat switch parameters listed below are Inactive.

• | Driver Seat Horizontal Switch

• | Driver Seat Cushion Front Vertical Switch

• | Driver Seat Cushion Rear Vertical Switch

• | Driver Seat Back Switch

⇒ | If not the specified value, test the appropriate signal circuit listed below for a short to ground. If the circuit tests normal, replace the K40 memory seat module.

• | Front vertical upward switch terminal A (LHD)

• | Front vertical upward switch terminal K (RHD)

• | Front vertical downward switch terminal K (LHD)

• | Front vertical downward switch terminal A (RHD)

• | Rear vertical upward switch terminal F (LHD)

• | Rear vertical upward switch terminal J (RHD)

• | Rear vertical downward switch terminal J (LHD)

• | Rear vertical downward switch terminal F (RHD)

• | Horizontal forward switch terminal D

• | Horizontal rearward switch terminal C

• | Recline forward switch terminal H

• | Recline rearward switch terminal G

4. Install a 3 A fused jumper wire between the ground circuit terminal E and the appropriate signal circuit terminal listed below. Verify the appropriate scan tool seat switch parameter is Forward/Rearward or Up/Down.

• | Front vertical upward switch terminal A (LHD)

• | Front vertical upward switch terminal K (RHD)

• | Front vertical downward switch terminal K (LHD)

• | Front vertical downward switch terminal A (RHD)

• | Rear vertical upward switch terminal F (LHD)

• | Rear vertical upward switch terminal J (RHD)

• | Rear vertical downward switch terminal J (LHD)

• | Rear vertical downward switch terminal F (RHD)

• | Horizontal forward switch terminal D

• | Horizontal rearward switch terminal C

• | Recline forward switch terminal H

• | Recline rearward switch terminal G

⇒ | If not the specified value, test the signal circuit for a short to voltage an open/high resistance. If the circuit tests normal, replace the K40 memory seat module.

5. If all circuits test normal, test or replace the S64D seat adjuster switch.

#### Seat Motor Control Circuit Test

1. Disconnect the X4 harness connector at the K40 memory seat module.
2. Verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.

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

3. Connect the X4 harness connector at the K40 memory seat module and 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

4. Connect a test lamp between control circuit terminal 1 and control circuit terminal 5.
5. Ignition ON, command the 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.

⇒ | If the test lamp remains OFF during either of the commands, test the control circuits for an open/high resistance. If the circuits test normal, replace the K40 memory seat module.

6. 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 S64D seat adjuster switch.
2. Test for infinite resistance between the ground terminal E and each signal terminal listed below with the switch in the open position.

• | Front vertical upward switch terminal A (LHD)

• | Front vertical upward switch terminal K (RHD)

• | Front vertical downward switch terminal K (LHD)

• | Front vertical downward switch terminal A (RHD)

• | Rear vertical upward switch terminal F (LHD)

• | Rear vertical upward switch terminal J (RHD)

• | Rear vertical downward switch terminal J (LHD)

• | Rear vertical downward switch terminal F (RHD)

• | Horizontal forward switch terminal D

• | Horizontal rearward switch terminal C

• | Recline forward switch terminal H

• | Recline rearward switch terminal G

⇒ | If not the specified value, replace the S64D seat adjuster switch.

3. Test for less than 1 Ω between the ground terminal E and each signal terminal listed below with the switch in the closed position.

• | Front vertical upward switch terminal A (LHD)

• | Front vertical upward switch terminal K (RHD)

• | Front vertical downward switch terminal K (LHD)

• | Front vertical downward switch terminal A (RHD)

• | Rear vertical upward switch terminal F (LHD)

• | Rear vertical upward switch terminal J (RHD)

• | Rear vertical downward switch terminal J (LHD)

• | Rear vertical downward switch terminal F (RHD)

• | Horizontal forward switch terminal D

• | Horizontal rearward switch terminal C

• | Recline forward switch terminal H

• | Recline rearward switch terminal G

⇒ | If greater than the specified range, replace the S64D seat adjuster switch.

#### 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. 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.

• | Front Seat Adjuster Switch Replacement

• | Front Seat Adjuster Motor Replacement

• | Front Seat Recliner Actuator Motor Replacement

• | Control Module References for memory seat module replacement, setup, and programming

## Power Seat Malfunction 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 | 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 from the appropriate F13UA, F12DA, or F13DA 25 A fuse located in the X51A I/P 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 switches for the seat directional motors listed below in both directions. The seat should move in the commanded direction.

• | M51D Horizontal Motor

• | M50D Front Vertical Motor

• | M55D Rear Vertical Motor

• | M56D 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. Ignition OFF, disconnect the harness connector at the appropriate S64 seat adjuster switch.
2. Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground:

• | Terminal B (AG1, AG2)

• | Terminal A (AG5)

• | Terminal C (AG5)

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the appropriate B+ circuit listed below and ground:

• | Terminal E (AG1, AG2)

• | Terminal D (AG5)

⇒ | 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 front vertical motor

• | M55 rear vertical motor

• | M51 horizontal motor

• | M56 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 test normal, 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 B+ terminal and each control terminal the with the switch in the open position.

⇒ | If less than the specified value, replace the S64 seat adjuster switch.

3. Test for less than 1 Ω between the B+ terminal and each control terminal with the 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 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:

• | 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. 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.

• | Front Seat Adjuster Switch Replacement

• | Front Seat Adjuster Motor Replacement

• | Front Seat Recliner Actuator Motor Replacement