Theory Of Operation
WARNING: This page is about a different car, the 2014 Dodge Journey. However, it is still accessible from the selected car via links, so may be relevant.
The objective of the Idle "Speed Rationality" is to monitor the ability to achieve and maintain a steady idle condition. The Engine Speed Error is calculated by comparing the difference between the Idle Set Speed from the Engine Speed and filtering the result. If engine speed does not come within a calibrated threshold of target idle speed, a timer is started. If the timer reaches its maximum threshold without the idle set speed returning inside of its calibrated threshold, a soft failure is generated.