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.