Hi MARRANT. Welcome to the forum. You don't want diagnostic fault codes to set, they indicate a problem that was detected. What your mechanic is referring to is the "readiness monitors". Those are a series of self tests the Engine Computer runs when the proper conditions are met. Your mechanic should be able to give you more specific requirements, but basically the conditions relate to length of time driving at a steady highway speed after the engine has reached normal operating temperature, there must be some speed changes, possibly including a burst of increased acceleration and / or coasting. Chrysler calls this a "global good trip" but I don't remember much more than that. I seem to recall two completed global good trips are required, meaning two separate drive cycles in a row, with the engine cooling down in between, and none of the tests will run if there is a diagnostic fault code stored in the Engine Computer. Most, but not all fault codes result in the Check Engine light being turned on.
There are also different methods of testing tail pipe emissions in different parts of the country. You might be able to request the typical tests with a gas analyzer probe stuffed up the tail pipe. This is necessary on older cars that don't have the self-test capabilities built in. The readiness monitors are considered a shortcut to the testing procedures. When they see that the self-tests have run and passed, they know there is no need for them to repeat the tests manually.
Sunday, October 3rd, 2010 AT 2:57 AM