Warning light

Check engine light came on after getting gas

Check the fuel cap first. On many cars, a cap that’s loose, missing or not clicked shut can turn on a steady check engine light. Expect the light to stay on for a few drives after you fix it.

Sources checked November 5, 2026 · Independent technician review pending · Report an error

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This guide is for a steady light. If the light is flashing or the engine is shaking, ease off and pull over safely. A loose cap doesn’t cause that.

Check the cap once you’re parked

Turn the engine off. Remove the cap and look at the rubber seal for cracks, tears or grit. Put it back and turn it until it clicks. Nissan’s Sentra guide says to turn it clockwise until you hear a single click. If the cap hisses as you loosen it, wait for the hissing to stop before taking it off. Ford gives the same warning, because the fuel system can be under pressure.

On a capless filler, open the fuel door and check that the inner flap has closed. Ford’s guidance for its Check Fuel Fill Inlet message is to clear visible debris by inserting the fuel nozzle or the supplied funnel.

Why the light stays on for now

The car has to run its fuel vapor leak test again before it turns the light off, and that test only runs under certain conditions. Nissan’s 2018 Sentra manual says the light should go off after a few driving trips if the cap was the only problem. If it doesn’t, have the car inspected.

You don’t need to clear the code. Leaving it alone lets you see whether the car agrees the problem is fixed.

What applies to most cars, and what depends on yours

Most gasoline cars sold in the US test the fuel vapor system for leaks, and a fuel cap that doesn’t seal is a common reason for that test to fail. That much applies broadly.

The details depend on the vehicle. How many trips the light takes to go off, whether a separate cap message appears, and how you dismiss it all vary. A 2022 Ram 2500 or 3500 has you tighten the cap and press the right arrow button to clear the message. Nissan says its LOOSE FUEL CAP message may take a few trips to appear in the first place. Some cars have no message at all. Your owner’s manual has the version that applies to you.

If you ran the tank empty

Running out of fuel can also turn on the light on some cars. Nissan’s 2018 Sentra manual lists it next to a loose cap, and tells owners to keep at least 3 gallons in the tank while the light clears. That figure is for that car, so check your own manual.

If the light doesn’t go off

Get the code read. A cap-related light usually sets an evaporative emissions (EVAP) leak code such as P0455, P0442 or P0456. Nissan’s bulletin for those three codes starts with the fuel cap and then moves on to the rest of the vapor system.

If the scan shows a misfire, fuel-trim or sensor code, the fill-up was probably a coincidence. Look up that code instead.

If you need a new cap

Buy one made for your vehicle. A cap that fits loosely or seals poorly can keep the light coming back. Bring the old cap or the year, make and model to the parts counter.