Can a loose gas cap cause the MIL to turn on?
Vehicles equipped with “OBD II” complete a series of manufacturer defined diagnostic checks for evaporative gas leaks – including very small leaks. A broken gas cap, or one not completely tightened, can cause MIL illumination. In these cases, the vehicle’s OBD II system is operating as designed as it has detected a fault condition. If you have reason to believe that the gas cap was not completely fastened, simply re-tightened the cap. The vehicle will continue to run its diagnostics. The vehicle will turn off the MIL after several “trips” if the fault condition no longer exists. Otherwise, you should have your vehicle evaluated, or “scanned,” to find the diagnostic fault code that caused the MIL to be illuminated. Continued operation of a vehicle with an illuminated MIL may result in significant damage to vehicle’s emission control system and greater repair costs.
