There are various ways the Check Engine light will act depending on the severity of the problem. The most serious is when it is flashing. That is very rare and means stop the engine right now before serious damage occurs to the catalytic converter. It is overheating due to excessive unburned fuel entering the exhaust system.
Anytime the Check Engine light turns on while driving, there will be a diagnostic fault code stored in the Engine Computer. Having that code read is the place to start. It will indicate the circuit or system with the problem, not necessarily the defective part. Many auto parts stores will read those codes for free. Don't put that off too long. If the problem doesn't act up again in the time you start the engine 50 times, the code(s) will erase automatically and that valuable information will be lost. Disconnecting the battery or running it dead will also cause the codes to erase.
Thursday, January 20th, 2011 AT 5:24 AM