For 1990-2009 cars

## DTC P1631 3.6L (LY7)

### 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 Descriptor

DTC P1631: Theft Deterrent Start Enable Signal Not Correct

### Circuit/System Description

The remote control door lock receiver (RCDLR) sends the fuel enable password to the engine control module (ECM) via the serial data circuit. The ECM verifies the fuel enable password received matches the password stored in memory. If the fuel-continue password is correct, the ECM enables the starting and fuel delivery systems. When replacing an ECM with a GM SPO replacement part, the new ECM will learn the incoming fuel enable password immediately upon request.

### Conditions for Running the DTC

• | The ignition is ON.

• | DTC P1631 runs continuously once the above conditions are met for about 5 seconds.

### Conditions for Setting the DTC

The ECM remains in theft deterrent password learn mode.

### Action Taken When the DTC Sets

• | It may be impossible to start the vehicle.

• | The instrument panel cluster (IPC) will illuminate the SECURITY indicator.

• | The ECM will not illuminate the malfunction indicator lamp (MIL).

### Conditions for Clearing the DTC

• | The history DTC clears after 40 malfunction-free warm-up cycles.

• | The DTC can be cleared with the scan tool.

### Reference Information

#### Schematic Reference

Theft Deterrent System Schematics

#### Connector End View Reference

Master Electrical Component List

#### Description and Operation

Content Theft Deterrent (CTD) Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

Use the scan tool to verify that DTC P1631 is not set.

⇒ | If the DTC is set, the password learn procedure is required to perform. If the DTC is set again, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the ECM replacement, set-up, and programming

## DTC P1631 4.6L (LH2)

### 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 Descriptor

DTC P1631: Theft Deterrent Start Enable Signal Not Correct

### Circuit/System Description

The remote control door lock receiver (RCDLR) sends the fuel enable password to the engine control module (ECM) via the serial data circuit. The ECM verifies the fuel enable password received matches the password stored in memory. If the fuel-continue password is correct, the ECM enables the starting and fuel delivery systems. When replacing an ECM with a GM SPO replacement part, the new ECM will learn the incoming fuel enable password immediately upon request.

### Conditions for Running the DTC

• | The ignition is ON.

• | DTC P1631 runs continuously once the above conditions are met for about 5 seconds.

### Conditions for Setting the DTC

The ECM receives an incorrect password from the RCDLR.

### Action Taken When the DTC Sets

• | It may be impossible to start the vehicle.

• | The instrument panel cluster (IPC) will illuminate the SECURITY indicator.

• | The ECM will not illuminate the malfunction indicator lamp (MIL).

### Conditions for Clearing the DTC

• | The history DTC clears after 40 malfunction-free warm-up cycles.

• | The DTC can be cleared with the scan tool.

### Reference Information

#### Schematic Reference

Theft Deterrent System Schematics

#### Connector End View Reference

Master Electrical Component List

#### Description and Operation

Content Theft Deterrent (CTD) Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

Use the scan tool to verify that DTC P1631 is not set.

⇒ | If the DTC is set, the password learn procedure is required to the DTC is set again, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the ECM replacement, set-up, and programming