For 1990-2009 cars

## 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 | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
B+ MSM Terminal 5 X3 | 1 | 1 | 1 | -- | --
B+ MSM Terminal 6 X3 | 2 | 2 | 2 | -- | --
B+ Seat Adjuster Switch | 2 | 1 | 1 | -- | --
Front Vertical Up Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Front Vertical Down Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Horizontal Forward Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Horizontal Rearward Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Rear Vertical Up Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Rear Vertical Down Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Recline Forward Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Recline Rearward Switch Signal | 2 | 1 | -- | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Driver Seat Front Vertical Motor Down Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2355 5A
Driver Seat Front Vertical Motor Up Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2355 5A
Driver Seat Horizontal Motor Forward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2375 5A
Driver Seat Horizontal Motor Rearward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2375 5A
Driver Seat Rear Vertical Motor Down Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2365 5A
Driver Seat Rear Vertical Motor Up Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2365 5A
Driver Seat Recline Motor Forward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B1825 5A
Driver Seat Recline Motor Rearward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B1825 5A
Ground - MSM Terminal 1 X3 | -- | -- | -- | -- | --
Ground - MSM Terminal 4 X3 | -- | -- | -- | -- | --
Ground - Inline X315 Terminal 5 | -- | 2 | 2 | -- | --
1. Power seat and memory functions inoperative 2. Scan Tool Does Not Communicate with Low Speed GMLAN Device

### Circuit/System Description

Battery positive voltage is supplied at all times to the memory seat module (MSM) from the 10A MSM fuse located in the I/P fuse block. This voltage is used by the MSM for logic power and to supply battery reference voltage to the seat and lumbar adjuster switches. Battery positive voltage is also supplied at all times to the MSM from the 25A LT/PWR/SEAT circuit breaker. This voltage is connected to a power rail internal to the MSM 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 MSM through 2 motor control circuits. The MSM 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 MSM checks to see if the reference voltage is shorted to ground or battery before enabling any of the seat, lumbar, or adjustable pedal 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 MSM. In response to this signal, the MSM 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 Memory Seat Module seat switch parameters while pressing the appropriate seat switch. The reading should change between Inactive and Active.

⇒ | 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 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 seat adjuster switch.
2. 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. If the circuit tests normal, replace the MSM.

3. Install a 3A fused jumper wire between the appropriate signal circuit listed below and the B+ circuit terminal E. Verify the scan tool seat switch parameter is Active.

• | Front vertical upward switch terminal A

• | Front vertical downward switch terminal K

• | Rear vertical upward switch terminal F

• | Rear vertical downward switch terminal J

• | 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 an open/high resistance. If the circuit tests normal, replace the MSM.

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

#### Seat Motor Control Circuit Test

1. Ignition OFF, disconnect the X3 harness connector at the MSM.
2. Ignition ON, 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. Ignition OFF, connect the X3 harness connector at the MSM and disconnect the harness connector at the appropriate seat motor.
4. Connect a test lamp between control circuit terminal 1 and control circuit terminal 2.
5. 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.

⇒ | 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 MSM.

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 seat adjuster switch.
2. Test for infinite resistance between each seat direction signal terminal listed below and the B+ terminal E with the switch in the open position.

• | Front vertical upward switch terminal A

• | Front vertical downward switch terminal K

• | Rear vertical upward switch terminal F

• | Rear vertical downward switch terminal J

• | 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 seat adjuster switch.

3. Test for less than 1 ohm between each seat direction signal terminal listed below and the B+ terminal E with the switch in the closed position.

• | Front vertical upward switch terminal A

• | Front vertical downward switch terminal K

• | Rear vertical upward switch terminal F

• | Rear vertical downward switch terminal J

• | 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 adjuster switch switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Power Seat Switch Replacement

• | Control Module References for MSM replacement, setup, and programming

## 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 | 1 | 1 | -- | --
Front Vertical Motor Up Control | 1 | 1 | -- | --
Seat Horizontal Motor Forward Control | 1 | 1 | -- | --
Seat 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 | -- | --
Ground - Seat Adjuster Switch | -- | 1 | -- | --
1. Power seats 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 switches from the LT/PWR/SEAT circuit breaker and the RT/PWR/SEAT circuit breaker that are 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.

### 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 directions.

• | Horizontal Motor

• | Front Vertical Motor

• | Rear Vertical Motor

• | 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

1. Disconnect the harness connector at the seat adjuster switch.
2. Ignition OFF, test for less than 1 ohm between the ground circuit terminal B and ground.

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

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

• | Terminal E (AH5/AAQ)

• | Terminal D (AG1/AG2)

⇒ | 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 appropriate seat motor.
2. Ignition ON, verify that the test lamp illuminates between control circuit terminal 1 and control circuit terminal 2 while pressing the seat switch in both directions.

⇒ | If the test lamp does not illuminate for both directions, 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.

3. 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 seat adjuster switch.
2. Test for infinite resistance between each control terminal and the B+ terminal with the switch in the open position.

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

3. Test for less than 1 ohm between each control terminal and the B+ terminal with the switch in the closed position.

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

4. Test for less than 1 ohm between each control terminal and the ground terminal with the switch in the open position.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Power Seat Switch Replacement

• | Front Seat Recliner Actuator Motor Replacement