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 continue 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 request.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1631 Theft Deterrent Fuel Enable Signal Not Correct
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The ECM receives an incorrect password from the RCDLR.
Action Taken When the DTC Sets
| • | The vehicle will not start. |
| • | The instrument panel cluster (IPC) will illuminate the SECURITY indicator. |
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
A GM SPO replacement ECM is in a functional state to learn the password from the RCDLR. If the RCDLR is replaced, the ECM must be placed in password learning mode to relearn the 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 .
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Important: You must diagnose any Bxxxx DTCs prior to diagnosing Pxxx DTCs. Perform the password learn procedure. Refer to Programming Theft Deterrent System Components . Does the DTC reset? | Go to Step 3 | Go to Step 4 |
3 | Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 4 | -- |
4 |
Important: Before clearing DTCs, monitor all DTC status parameters and note any additional DTCs.
Does the engine start and operate normally? | System OK | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
