When it comes to the subject of readiness monitors, there’s a fine line between the simplicity and complexity of it. To start with, one of the many jobs of the PCM or ECM in a vehicle is to monitor all of the emission related systems, store data that can be referenced when any given system is not working properly, and naturally store a trouble code if a problem is detected.
Due to the importance of vehicle emission systems, these monitors are in place as a proactive means of checking them. Instead of waiting for an indication that a system is not working as efficiently as it should, they are a way for the control unit to initiate a self-check to look at or “monitor” their operation. They are basically the “micro-manager” of the automotive PCM.
There are two different types of monitors, continuous and non-continuous. Continuous monitors are checking systems that allow for immediate results, in other words they perform the check so quickly that they will indicate “ready” or “complete” on your scan tool at all times. If a problem occurs, the control unit will recognize it right away and potentially store a trouble code.
Non-continuous monitors are named as they are because they need a number of different conditions to be met before they are considered complete.