OBD-II systems are designed to alert drivers when something in the engine or emission control system begins to deteriorate or fail. When the OBD-II system determines that a problem exists a code is stored in the computer memory. The computer may illuminate a dashboard light indicating “Service Engine Soon” or “Check Engine.”
This light informs the driver that there is an emission-related engine problem. If the light is on, there is a real problem relating to emission control that needs to be fixed. If the light is flashing the driver needs to take the car to a repair technician as soon as possible.