DTC P1631 Theft Deterrent Start Enable Signal Not Correct. Buick GL7 (Export) 2000

For 1990-2009 cars

### Circuit Description

The powertrain control module (PCM) controls the fuel injector operation and the starter operation based on a vehicle theft deterrent (VTD) password from the theft deterrent module. When the ignition is first turned ON, the theft deterrent module sends a programmed theft deterrent password to the PCM. The PCM acknowledges the password and responds to the VTD module that normal fuel injector and starter operation will continue. If the PCM detects an incorrect password due to a theft deterrent system failure or an attempted vehicle theft, DTC 1631 will set. The engine will not crank as long as the condition is present. Refer to Diagnostic System Check - Theft Deterrent and Vehicle Theft Deterrent (VTD) Operation in Theft Deterrent.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

• | The PCM detects an incorrect password from the VTD system.

• | The condition is present for less than 1 second.

### Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC clears after 40 malfunction free warm-up cycles.

• | The PCM receives a clear code command from the scan tool.

### Diagnostic Aids

DTC P1631 indicates that the vehicle theft deterrent password the PCM has learned does not agree with the password being received from the theft deterrent system. This condition can occur if an incorrect key is used when attempting to start the vehicle or if the VTD module has been replaced and the PCM Password Learn function has not been enabled. If the VTD module has been replaced, the password must be relearned.

#### DTC P1631 Incorrect Theft Deterrent Start Enable Signal

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Perform the password learn procedure. Refer to Diagnostic System Check - Body Control System in Body Control System. Can the password learn procedure be performed successfully? | -- | System OK | Go to Diagnostic System Check - Theft Deterrent in Theft Deterrent