What 3 things and in order can I DIY for p0456. Hard start after fueling every time and irregular idle when stopping at lights. P0456 and no other indicator lamps coming on. Didn't replace gas cap.

  • Welcome to Motor Vehicle Maintenance & Repair! What is the year/make/model/engine of the vehicle in question? Mar 15 at 20:03
  • Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
    – Community Bot
    Mar 16 at 18:15

1 Answer 1


Code P0456 refers to a small emissions system leak. It is usually caused by driver error like running the engine while refueling. A poorly tightened gas cap could trigger it along with other codes as well.

Other worse case scenarios possibilities: Cracked hoses around purge or control valves. Defective charcoal canister. One thing I discovered that overfilling the gas tank can destroy the charcoal canister because of liquid fuel instead of fuel vapor entering- stop at the first click. Electrical issues with purge or control valves. Defective fuel tank caused by rust hole forming.

Change fuel cap if seal or the check valve is damaged.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .