Why is the Engine Light ON?
If the light comes ON and stays ON, the On-Board Diagnostic (OBD) system has detected a problem. The OBD system monitors the vehicle's performance and regulates engine speed (RPM), fuel mixture, and ignition timing.
Engine Light common causes:
Loose or damage gas cap: The gas cap is used to hold and maintain pressure in the gas tank. A loose or damaged gas cap will cause gasoline fumes to escape the gas tank into the atmosphere. Re-tightening or replacing the gas cap will fix the problem.
Damage catalytic converter: The catalytic converter helps convert harmful exhaust gas into an environmentally friendly gas. Deterioration of the catalytic converter will trigger the engine light. Replacing the catalytic converter will fix the problem. If the catalytic converter is not damaged, using high octane gas for a couple of weeks may repair the problem.
Damage Oxygen (O2) Sensor(s): The oxygen sensors measure the amount of unburned oxygen exhausted by the engine. Replacing the oxygen sensor will fix the problem.
Engine Light other common causes:
How to read engine codes
An OBDII scanner is the best alternative to read codes, although some manufacturers have instructions on how to read the code using the engine warning light, using an OBDII scanner is more accurate.
How to clear or erase engine light
After the problem is fixed, the engine light can be cleared with an OBDII scanner or by disconnecting the car battery for more than 30 minutes.