Why is my chevy cruze 2015 check engine light on?

If the "check engine" light is illuminated in the Chevy Cruze it is usually related to an emissions leak. You may notice the smell of gas and a reduction in fuel economy. Check for a loose gas cap. When tightened, the light will go off. Other causes include a faulty fuel tank pressure relief valve. If the Cruze recently had its oil changed, a loose oil filter, filler cap or poorly inserted dipstick can trigger the warning. Also starting and stopping excessively can stress the catalytic converter. Try driving at highway speeds for 15-20 minutes to clear the CEL. If none of this works, consider the warning is indicating there's an issue with the transmission, O2 sensors or spark plugs and get a technician to use and OBDII scanner to diagnose the problem.