Hello and thank you for using Just answer! I'm Billy and i will assist you with this. Feel free to ask if you need any further info.
When the engine management system detects a fault, it will trigger the warning light.
Subsequently, it will store fault codes in system memory.
These fault codes can be retrieved using a scan tool. These should identify the faulty component(S) or wiring.
Sometimes, you get a "ghost fault", meaning fautl codes stored and warning light on, for no apparent reason........and in this case, resetting the system, and erasing the fault code, will turn the light off...........no repair is necessary.
To find out, if you have this case......or another, you may remove battery negative cable for a few minutes, as this should erase the codes and reset the systems............be aware that this will also reset the trip meter, the clock, and the radio code........so you will need radio code upon refitting, if radio is equiped with antitheft.
Having reset (using scan tool, or battery removal), if the light gets back on, and stays on, then there is a problem........and the next step would be retrieving the fault code and proceed accordingly (as the code will identify the culprit).
Thank you for trusting JA and myself.......get back to me if further info is needed.....positive feedback and bonuses appreciated...http://www.justanswer.com/car/expert-billy/