Nissan and Infinity have had transponder key immobilizer systems since 1999. The 1999 to 2004 systems
are typically structured around the engine control module (ECM) and immobilizer control (Immo) units directly
communicating with each other over a dedicated single communication wire. Some 2004 and forward systems are body
control module (BCM) to Immo control unitbased. We will focus on the ECM-based systems in this article, and cover
the BCM-based systems in a future article.