When the Check Engine Light is illuminated, the vehicle may perform normally or it may experience issues such as poor acceleration, a rough idle, stalling, and/or poor fuel economy. In some cases, the vehicle may misfire and the Check Engine Light may flash on and off. Whenever the Check Engine Light comes on, it is important to have a Check Engine Light Diagnosis.
A Check Engine Light Diagnosis involves special computer system scan tools, fuel pressure and electronic testing equipment, specialized technician training, and even licensing in many states. Merely retrieving a code and trying a part, without a Check Engine Light Diagnosis, will do little to repair the problem and may even damage expensive emission control system components.
The purpose of this article is to provide an outline for some of the essential steps involved in performing an Check Engine Light Diagnosis. This guide can be used—by you and the shop—to track the progress as the mechanics perform the test.