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 enable password is correct, the ECM enables the starting and fuel delivery systems. When replacing a ECM with a GM SPO replacement part, the new ECM will learn the incoming fuel enable password immediately upon receipt.

This diagnostic procedure supports the following DTC:

DTC P1629 Theft Deterrent Fuel Enable Signal Not Received

The ECM receives an incorrect fuel enable password.

A fault in the serial data line communication between the RCDLR and the ECM will set DTC P1629. The missing information will inhibit the ECM to receive the fuel enable password from the RCDLR. In this case, a U code will be set, and in order to ensure the correct system diagnosis, make sure all U codes must be correct before performing DTC P1629 diagnosis.

The engine control module with an GM SPO replacement part is in operative state so as to learn the password from the CTD control module. If the theft deterrent control module is replaced, the ECM must be placed in password learning mode to relearn a new password. Once learned, the password becomes permanent information that remains in the ECM. The loss of ECM battery or ignition voltage does not affect the programmed password information. Refer to Programming Theft Deterrent System Components.

The following numbers are corresponding to the steps in the diagnostic table.

3. To set this code, the password that the ECM has learned does not agree with the password being received from the theft deterrent control module or the ECM did not received the password from the theft deterrent control module. This condition can occur if the theft deterrent control module has been replaced and the Programming Theft Deterrent System Components procedure has not been performed.

5. If the ECM resets the DTC after the programming theft deterrent system components procedure has been performed, the theft deterrent control module is malfunctioning.