Theory Of Operation
WARNING: This page is about a different car, the 2010 Dodge Charger and 2010 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.
The objective of the Idle Speed Rationality monitor is to evaluate the ability of the idle speed control system to achieve and maintain a steady idle, by monitoring engine RPM during idle. If engine RPM is not within a calibrated dead band of target idle speed, a timer is started. If the timer reaches a maximum threshold without any sign of the RPM trending towards control, a fault is generated.