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Evap System Large Leak Detected. In this guide, you will learn about P0455 common causes, diagnosis, and repair procedures. 

Table of Contents

System gross leak evaporative emissions (often associated with P0440 code).

P0455 indicates a large leak in the vapor recovery system.


  • Check engine light
  • Possible gasoline smell around the filler or tank area
  • Decrease in MPG


  • Missing/broken fuel cap - You forgot to tighten or place the gas cap back on. 
  • Missing/broken fuel cap seal - The rubber seal on the gas cap can get damaged over time. 
  • Leaks in hoses on the breather system - hoses tend to dry-rot and crack over time.
  • Leak in filler neck hose - The hose from the fuel tank to the fuel gas cap can get damaged. 
  • Plugged fuel tank purge valve - Purge valve can fail and may need to be replaced. 
  • Fuel tank leak - The fuel tank may be damaged due to rust or accident. If you notice gasoline on the ground, have your vehicle repaired immediately. 
  • Fuel tank accessories(such as the fuel level sender) gasket can be leaking.

Vehicles with charcoal filters in the evaporative emissions system need to have the filter inspected for cracks, damage, and leaks.

Even though the code says, it’s a large leak, in reality, the leak could be as small as a pinhole.

Common Repairs

bad gas cap fault code
  • Replacement of the fuel cap.
  • Replacement of the fuel tank filler neck
  • Repair/replacement of hoses associated with the EVAP system.


diagnose p0455 fault code

Troubleshooting fault code P0455 can be very challenging. If the problem is not the gas cap, you should seek the help of a certified auto mechanic. In most cases, finding fuel system leaks is not an easy process a car owner can perform at home. 

If you do not see any signs of leaks, you can use a scan tool and reset the engine codes. Take the vehicle for a test drive and see if the code reappears.

If the code does reappear and there are no signs of leaks, then there may be a sensor or sensor wiring that is setting the CEL.

Follow OEM recommended troubleshooting to repair any electrical problems. If the issue is still unresolved, then take it to a licensed shop to conduct a smoke test to detect leaks too small to be seen.

The P0455 code will not affect the vehicle's drivability; however, excessive fuel consumption can be seen depending on where the fault is. That is why it is important to have the CEL diagnosed and repaired as soon as possible.