P0455 Evaporative Emission System Leak Detected (Gross Leak/No Flow)
Are you experiencing poor gas mileage along with the P0455 code? Unfortunately, you might have an issue with the EVAP system.
So the P0455 code stands for Evaporative Emission System Leak Detecteted. This code will be set when you have a large leak in the EVAP system. In some situations, you could have a vapor blockage in the EVAP system, which the ECM could interpret as a leak.
So what’s the EVAP system? Well, the purpose of the EVAP system is to store fuel vapors created in the fuel tank and transfer them into the combustion chamber through the intake manifold where they get burned off in the process.
Now, let’s go over the potential components in the EVAP system that can trigger the P0455 code.
Common causes
Fuel cap
One common cause of the P0455 code is a faulty fuel cap. If the fuel cap is damaged or has a torn gasket, it won't create a proper seal. This creates a gap for the fuel vapors to escape, leading to a leak in the system. Also, always make sure you hear at least 3 clicks when closing the gas cap. If you don’t close it properly, this can trigger the P0455 code, as well.
Fuel Tank Filler Neck
The second cause for the P0455 code is a faulty fuel tank filler neck. If it’s corroded, damaged, or cracked, fuel vapor can escape and cause a leak in the system.
Stuck-open purge valve
The third potential cause for the P0455 code is a stuck-open purge valve. The purge valve opens when the ECM commands it to transfer fuel vapors from the charcoal canister into the engine for combustion. Under normal operating conditions, the purge valve remains closed and only opens during the purging process as directed by the ECM. If the purge valve gets stuck open when it should be closed, it creates a constant vacuum in the EVAP system, leading to the P0455 code.
In some situations, I’ve also seen a stuck-closed purge valve that can cause this code.
Charcoal Canister
The fourth cause for the P0455 code is a bad charcoal canister. If it is damaged or has any large cracks in it, fuel vapors can escape, creating a leak in the EVAP system.
Fuel tank pressure sensor
The next possible cause for the P0455 code is a malfunctioning fuel tank pressure sensor. The purpose of this sensor is to monitor the pressure in the fuel tank and send this information to the ECM. If the fuel tank pressure sensor is faulty, it can send false readings of the pressure to the ECM, making it believe that there’s a leak in the system. The car’s computer will then turn on the check engine light and set the P0455 code.
Evap hoses
Another cause of the P0455 code is defective EVAP hoses. If any hoses have cracks or get damaged, it can cause a large leak. Also, sometimes one of these hoses can become loose, which will cause a leak, as well.
EVAP canister vent valve
The next thing on our list is an EVAP canister vent valve. This component is supposed to be open during normal operation and closed when the ECM tests for leaks. If the canister vent valve remains open during testing, the ECM will interpret this as a large leak, and trigger the P0455 code.
Fuel tank
Another component that can cause a P0455 code is a damaged fuel tank. This isn’t very common, but it’s still possible.
Engine control module
The last component that can trigger the code is a bad engine control module. However, this should always be your last option. I recommend testing all the other parts first, before blaming the ECM for the P0455 code.
One of the best ways to find a leak in the EVAP system is to use a smoke machine.
