Circuit Description
The powertrain control module (PCM) controls fuel injector and starter operation based upon a vehicle theft deterrent (VTD) password from the vehicle body control module (BCM). When the ignition is first turned on, the BCM sends a programmed VTD password to the PCM. The PCM acknowledges the password and responds to the BCM that normal fuel injector and starter operation are to continue. If the PCM detects an incorrect password due to VTD system failure or attempted vehicle theft, DTC 1631 is set. The engine does not start or crank as long as the condition is present.
Conditions for Setting the DTC
| • | The PCM is detecting an incorrect vehicle theft deterrent password from the VTD system. |
| • | The conditions is present for less than 1 second. |
Action Taken When the DTC Sets
| • | The PCM stores the conditions which were present when the DTC set as Fail Records data only. |
| • | The PCM disables the fuel injectors. |
Conditions for Clearing the MIL/DTC
| • | A history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
DTC P1631 indicates that the VTD password that the PCM has learned does not agree with the password being received from the VTD system. This condition may occur if an incorrect key is being used when attempting to start the vehicle or if the BCM is replaced and the PCM's password learn function is not enabled. If the BCM is replaced, the password must be relearned.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic System Check? | -- | ||
2 | Perform the password learn procedure. Can the password learn procedure be performed successfully? | -- | System OK | Go to Diagnostic System Check - Theft Deterrent in Theft Deterrent |
