DTC P1629 for Cadillac STS 2009

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 P1629: Theft Deterrent Fuel Enable Signal Not Received

The theft deterrent module (TDM) sends the start enable password to the engine control module (ECM) via the serial data circuit. If the start enable password is not received by the ECM in a specified amount of time, the ECM will disable vehicle starting.

Conditions for Running the DTC

•	Ignition is in the ACCESSORY or RUN position.

•	The ECM is not in learn mode.

Conditions for Setting the DTC

The ECM does not receive the start enable password from the TDM within the required amount of time.

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 start enable password 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 start enable password was not received within the required time. 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

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