Circuit Description
The engine control module (ECM) initiates engine operation based on the immobilizer password received from the vehicle immobilizer, or vehicle theft deterrent (VTD) control module. The ignition key head contains a transponder that emits a magnetic field. This magnetic field interacts with the magnetic field generated by the coils of the theft deterrent control module creating a voltage. This voltage signal becomes the immobilizer password that is sent to the ECM. If the password is incorrect, or cannot be read by the ECM, DTC P1631 is set.
DTC Descriptors
This diagnostic procedure supports the following DTC:
DTC P1631 Invalid Data Received From Vehicle Immobilizer Control Module
Conditions for Running the DTCs
| • | The ignition is ON and the engine is cranking. |
| • | The DTC P1631 diagnostic runs once per drive cycle. |
Conditions for Setting the DTC
The ECM has received invalid data from the VTD control module
Action Taken When the DTC Sets
| • | The DTC P1631 is stored in the ECM. |
| • | Engine control system functions are disabled and the engine will not start. |
Conditions for Clearing the DTC
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction. |
| • | The scan tool can clear the DTC from the module memory. |
Diagnostic Aids
Attempting to start the vehicle by bypassing the VTD system or by substituting parts without performing the Programming Theft Deterrent System Components procedure will continue to cause a no start condition.
Step | Action | Yes | No |
|---|---|---|---|
1 |
Is DTC P1631 present? | Go to Diagnostic System Check - Theft Deterrent in Theft Deterrent | Go to Intermittent Conditions |
