If an engine light comes up on your dashboard, and after using a scan tool to read the error, it comes up with a P0455 error code, there are some common causes.
The causes will be the same for Ford, Dodge, Chevy, or any foreign and domestic vehicle.
What is a P0455 OBDII Error Code?
A P0455 Code is an “Evap System Large Leak Detected“.
The Evap system is a part of emissions and helps stop vapors in the gas tank escaping into the atmosphere.
A standard Evap system has several components which keep the gas tank sealed and fed fumes back into the engine to be burnt away.
How Is a P0455 Code Fixed?
A P0455 error coed is usually fixed by using a smoke machine that feeds smoke into the Evap system and comes out the leak.
Most mechanic shops will use a smoke machine since it makes the leak much easier to find.
If no smoke machine is available, check all the major components in the Evap system for a leak and replace any suspected bad parts.
Read here for more on smoke machines.
Causes and Fixes of a P0455 OBDII Engine Error Code
- Gas Cap
- Evap Hose Leak
- Vent Valve
- Purge Valve
A bad or loose gas cap will cause a P0455 and is the most common fix.
Often the cap simply was not put back on, but a bad one can also cause this error.
Tighten the cap; if the code comes back, replace it. If the code comes back again, the problem is elsewhere.
A hose that is damaged or old cracked, and leaking can cause a P0455 code.
Most mechanics will use a smoke machine to find an Evap leak since they can be hard to spot.
A smoke machine feeds smoke into the system and will come out of the leaking location.
The hoses can also be examined for damage, but often, finding a leak in the Evap system is difficult without a smoke machine.
The vent valve allows the system to vent when needed.
If the vent valve goes bad and is stuck open it can cause a leak in the system.
The vent valve is usually located on the charcoal canister near the gas tank, but be sure to read the manual for the location on your vehicle.
A bad purge valve can cause a P0455 error code.
The purge valve is located in the engine bay and will have two hoses on it.
A purge valve opens and closes to let the vapors from the gas tank into the engine to be burnt away.
While the vehicle is off, the valve will close, and when the vehicle is running, it will open.
Is it OK to Drive With an P0455 Code?
Yes, it is usually safe to drive with a P0455 Code, but the vehicle may use more gas and not pass an emission test.
If an emission test needs to be done, the problem will need to be fixed, or the vehicle will fail the test.
A P0455 Code will usually not affect the performance of the engine, and the car or truck will continue to operate.
Summary
The above are the most common causes for a P0455 code, but of course, it could be something else.
For example, if a gas tank was somehow damaged, creating a hole can also potentially create the same error.
Wiring can also cause an error with a bad connection giving the computer the wrong results.
Most of the time, it is a bad gas cap, but if after replacing it, the code comes back, a leak or the Evap Canister Vent Valve would be the next likely problem.
A mechanic with a good scan tool and a smoke machine can tell what has gone bad, which usually costs.
If the Vent Valve is easy to get to, it may be worth replacing once the gas cap has been ruled out.
Keep in mind there are other problems that can cause this error, such as wiring with the below options the most common.
Of course, if in doubt, always take your vehicle to a certified mechanic.