Circuit Description
The engine control module (ECM) controls the starter operation based on 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 theft deterrent password to the ECM. The ECM acknowledges the password and responds to the BCM that normal starter operation will continue. If the ECM detects an incorrect password, a theft deterrent system failure, or an attempted vehicle theft, DTC 1631 will set. The engine will not start as long as the condition is present.
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 ON.
Conditions for Setting the DTC
| • | The ECM detects an incorrect password from the VTD system. |
| • | The condition is present for less than 1 second. |
Action Taken When the DTC Sets
| • | The ECM will not illuminate the malfunction indicator lamp (MIL). |
| • | The ECM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data. |
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
DTC P1631 indicates that the vehicle theft deterrent password that the ECM has learned does not agree with the password received from the VTD system. This condition can occur if an incorrect key is used when attempting to start the vehicle, or if the BCM has been replaced and the ECM Password Learn function has not been enabled. If the BCM has been replaced, the password must be relearned.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Perform the Password Learn Procedure. Refer to Programming Theft Deterrent System Components . Did you complete the procedure? | System OK | -- |
