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 and overview of each diagnostic category.

### DTC Descriptor

DTC P1629: Theft Deterrent Fuel Enable Signal Not Received

### Circuit/System Description

The theft deterrent module (TDM) sends the fuel enable password to the engine control module (ECM) via the serial data circuit. If the password sent by the TDM equals the password stored in the ECM, the ECM will allow vehicle starting.

### Conditions for Running the DTC

• | Ignition is in the RUN position.

• | The ECM is not in learn mode.

### Conditions for Setting the DTC

The ECM does not receive the fuel enable password from the TDM within 2 seconds.

### Action Taken When the DTC Sets

The security indicator will illuminate.

### Conditions for Clearing the DTC

• | A current DTC P1629 will be cleared when a fuel enable signal is received.

• | A history DTC will be cleared after 40 malfunction-free ignition cycles or when a scan tool is used to clear DTCs.

### Diagnostic Aids

DTC P1629 is an indicator that the fuel enable signal was not received within the required 2 second window. This does not necessarily indicate a fault is present with the TDM or ECM. Factors such as a long engine crank, a delay in the serial data communication, or B-codes set in the TDM will cause DTC P1629 to set. This DTC should not be used as a fault indicator, but rather as a symptom to assist in the diagnosis of these other systems.

### Reference Information

#### Schematic Reference

Immobilizer Schematics

#### Connector End View Reference

Immobilizer Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions