There is a diagnostic fault code in memory. If this was an intermittent problem, restarting the engine would restore normal operation but if the problem that was detected is relatively serious, the check engine light will still turn on any time the engine is running. That is the second most serious type of code, but that does not necessarily mean the problem was serious. The check engine light turns on when the fault code relates to something that could adversely affect emissions. When those problems act up, the light will be on.
It is when the problem is intermittent or a one-time thing that those fault codes become extremely valuable. If the problem is the least severe, the light will go off while you are driving when the problem stops acting up. If it is a little more severe, the light will turn on when the problem occurs, and if the problem clears up, the light will stay on until you turn the ignition switch off and restart the engine.
The most serious problems are when the check engine light is flashing. That means too much unburned fuel is going into the exhaust system where it will overheat and damage the catalytic converter. You should stop the engine right away to prevent that.
The people at many auto parts stores will read the fault codes for you for free. Be sure to record the code numbers. We can look up the descriptions here.
Tuesday, July 5th, 2016 AT 9:58 PM