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Q: Check Engine Light is on - code P0455

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My car had check engine light on and it was code P0455. I had the fuel pressure regulator and the purge valve replaced. I also replaced the fuel cap three times. Two days after the repairs the engine light came back. Now that it has been nearly a month after the repairs, the engine light turned off by itself as I was driving in the highway. My question is does it take time for the car computer to detect the new replaced parts? Is the problem still there even if the light is off or was there no problem with my car after all? I checked under the car many times, there is no fuel smell, no damaged hoses or fuel line, the canister is in great condition. By the way, one day as I was in a red light, the car RPM went down and the car turned off, but restarted with no problem. Does this has anything to do with code P0455.

My car has 82212 miles.
My car has an automatic transmission.

A: Hello. P0455 is the trouble code for a larg...

Hello. P0455 is the trouble code for a large leak detected by the evaporative emissions control system. The computer will set off this code if it detects a large leak in the evaporative emissions (EVAP) system. The EVAP emissions system is an emission system found on most modern vehicles. It’s purpose is to reduce the vehicle’s fuel vapor emissions by collecting them for ingestion by the engine. The system uses a serious of sensors and valves to monitor, collect, and purge the fuel vapors, reducing overall emissions levels.

In regards to time having to pass for the computer to detect repairs, yes, in some cases the vehicle will have to be driven for a few cycles before the computer detects that the issue is gone. If the repairs were made and the light has turned off on it’s own, then it is likely that the issues are resolved. If they were not, the light would not turn off or would come on again. In regards to your stalling issue, in most cases an EVAP code will not cause stalling. Usually, stalling is caused by a fuel or engine management issue.

If the stalling persists, I would have a professional technician, such as one from YourMechanic, come to your location to determine why the car is stalling and make any repairs necessary to get your car back in working order.

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