For 1990-2009 cars

### 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.

### DTC Descriptors

DTC B1735 01: Seat Front Up Switch Circuit Short to Battery
DTC B1740 01: Seat Front Down Switch Circuit Short to Battery
DTC B1745 01: Seat Rear Up Switch Circuit Short to Battery
DTC B1750 01: Seat Rear Down Switch Circuit Short to Battery
DTC B1755 01: Seat Assembly Forward Switch Circuit Short to Battery
DTC B1760 01: Seat Assembly Rearward Switch Circuit Short to Battery
DTC B1815 01: Seat Recline Forward Switch Circuit Short to Battery
DTC B1820 01: Seat Recline Rearward Switch Circuit Short to Battery

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Front Vertical Up Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Front Vertical Down Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Rear Vertical Up Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Rear Vertical Down Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Horizontal Forward Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Horizontal Rearward Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | --
Recline Forward Switch Signal | 2 | 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 | --
1. Power seat inoperative 2. Scan Tool Does Not Communicate with Low Speed GMLAN Device

### Circuit Description

When the power seat switches are pressed, they send a 12 V signal through the switch signal circuits to the memory seat module (MSM). The MSM then commands the driver seat motors to move in response to the switch signals.

### Conditions for Running the DTC

The MSM must be powered.

### Conditions for Setting the DTC

• | If a seat switch circuit is active in one direction and the switch for the opposite direction is pressed, this DTC will set.

• | A short to voltage on a switch signal circuit.

### Action Taken When the DTC Sets

• | A motor output driven in response to a switch considered failed is deactivated for both directions.

• | All memory recall commands are ignored.

• | The MSM will respond to any other switch signal that has not set a DTC.

### Conditions for Clearing the DTC

• | A current DTC will transition to history 3 seconds after the fault is no longer present and the ignition is cycled OFF then back to ACC or RUN.

• | The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.

### Reference Information

#### Schematic Reference

Driver Seat Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

• | Power Seats System 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

Ignition ON, observe the scan tool Memory Seat Module seat switch parameters while pressing the appropriate seat directional switches. The reading should change between Inactive and Active.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
2. Ignition ON, verify the scan tool seat switch parameters listed below are Inactive:

• | Front Vertical Upward Switch

• | Front Vertical Downward Switch

• | Rear Vertical Upward Switch

• | Rear Vertical Downward Switch

• | Horizontal Forward Switch

• | Horizontal Rearward Switch

• | Recline Forward Switch

• | Recline Rearward Switch

⇒ | 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 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

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

### Component Testing

1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
2. Test for infinite resistance between the B+ terminal E and each signal terminal listed below and 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 Ω between the B+ terminal E and each signal terminal listed below and with the appropriate 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 seat adjuster 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