Spark Plug Switching Control
WARNING: This page is about a different car, the 1985 Nissan Stanza. However, it is still accessible from the selected car via links, so may be relevant.
The spark plug switching control system is designed to change the ignition system from 2-plug to 1-plug ignition during heavy load driving in order to reduce engine noise. The system also functions to advance ignition timing by a specified value during 1-plug ignition.