the check engine light usually means that a code has been stored in the ECU for the engine. the code corresponds to a particular system in the engine that has failed. for example, if a o2 sensor went bad, the ECU would store a code dealing with the o2 sensor or its subsystem. now, to get the code, you should be able to goto autozone and have them read the code for you. they have a code scanner that reads the code from the ECU.