Circuit Description
The body control module (BCM) sends fuel enable password to the powertrain control module (PCM) via the serial data circuit when the ignition is ON and the BCM has read a learned transponder value from the key. The PCM verifies the fuel enable password to the fuel enable password stored in memory. If the fuel enable password is correct, the PCM enables starting and fuel delivery systems. When replacing a PCM with a GM SPO replacement part, the new PCM will learn the incoming fuel enable password immediately upon receipt.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1631 Theft Deterrent Start Enable Signal Not Correct
Conditions for Running the DTC
The ignition is switched to CRANK then to ON.
Conditions for Setting the DTC
The PCM receives an incorrect fuel enable password from the BCM.
Action Taken When the DTC Sets
| • | The vehicle will not start. |
| • | The driver information center (DIC) displays Starting Disabled Due To Theft message. |
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
Conditions for Clearing the MIL/DTC
| • | The PCM clears the current status of the DTC when it receives a valid fuel enable password from the BCM. |
| • | 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
DTC P1631 indicates that the PCM has received an incorrect password from the theft deterrent control module. This condition can occur if an incorrect key is being used when attempting to start the vehicle or if the BCM has been replaced and the PCM password learn function has not been enabled.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Verifies if the condition for setting DTC B2960 is present.
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To set this code, the password that the PCM has learned does not agree with the password being received from the BCM. This condition can occur if the BCM has been replaced and the programming theft deterrent system components procedure has not been performed.
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If the PCM resets the DTC after the programming theft deterrent system components procedure has been performed, the BCM 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 in Vehicle DTC Information |
Is DTC B2960 set as a current code? | Go to DTC B2960 | Go to Step 3 | |
|
Important: If a 10-Minute or 30-Minute Relearn Procedure is performed, all keys not learned at that time will be erased and will not be recognized. Perform the Adding Keys procedure on all keys or instruct the customer how to perform the Adding Keys procedure. Refer to Adding Keys . Perform the Programming Theft Deterrent System Components procedure. Refer to Programming Theft Deterrent System Components . Is the procedure complete? | Go to Step 4 | -- | |
4 |
Does the DTC reset? | Go to Step 5 | System OK |
|
Important: If a 10-Minute or 30-Minute Relearn Procedure is performed, all keys not learned at that time will be erased and will not be recognized. Perform the Adding Keys procedure on all keys or instruct the customer how to perform the Adding Keys procedure. Refer to Adding Keys . Replace the body control module (BCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | -- | |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
