For 1990-2009 cars

### Circuit 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 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.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1629 Theft Deterrent Fuel Enable Signal Not Received

### Conditions for Running the DTC

• | The ignition is ON.

• | DTC P1629 runs continuously once the above conditions are met for about 5 seconds.

### Conditions for Setting the DTC

The ECM receives an incorrect fuel enable password.

### Actions 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 MIL/DTC

• | The history DTC clears after 5 malfunction-free warm-up cycles.

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

### Diagnostic Aids

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.

### Test Description

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

1. 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.

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

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Theft Deterrent System Schematics Connector End View Reference: Theft Deterrent System Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Perform the Programming Theft Deterrent System Components procedure. Refer to Programming Theft Deterrent System Components. Is the procedure complete? | Go to Step 3 | --
3 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 4

System OK

4 | Replace the remote control door lock receiver (RCDLR). Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | Go to Step 5 | --
5 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK