Today's cars and trucks use many sensor, switches, solenoids, and other electrical components to control or monitor every aspect of the engine.From controlling the fuel and ignition systems, to monitoring the emissions. A problem in any of these systems, or subsystems, can cause the check engine light to come on.
The first step in diagnosis of the check engine light is to get the engine computer, called the PCM or ECM scanned for codes. Any time this warning comes on, a code is stored in the computer memory along with many data parameters that were present at the time of the fault.
A simple code reader that can be purchased at any automotive supplier can retrieve these codes. Many of the large national parts store chains will scan the system at no charge. The code will give an indication as to what system has / had a problem. The more expensive scanners will also show live data, and allow further diagnosis by being able to control parts of a particular system.
Flashing Engine Light
A flashing check engine light is an indication that there is an engine misfire that is severe enough to cause damage to the catalytic converter. This problem needs to looked at by a mechanic right away. A bad catalytic converter is very expensive to fix. From the factory, they can cost as much as $1300 parts and labor. The cheaper parts that can be purchased at many of the local repairs shops or national chains are just that, cheap. We have seen many times a customer with an engine light related to the converter has one of these cheaper parts installed, and the light comes back on. They do not want to hear that they need a new converter because the one they bought is not efficient enough, so the warning came back on the dash. You DO get what you pay for in auto repair.