P0441 - Evaporative Emission Control System Incorrect Purge Flow
P0455 - Evaporative Emission Control System Leak Detected (gross leak)
When the gas in the tank warms up, it expands, and years ago was just vented out to the atmosphere. Now the fuel supply systems are sealed and the fumes are collected and stored in a charcoal canister. When the engine is running and certain conditions are met, the Engine Computer opens the "purge" valve, then those stored fumes are drawn out of the canister to be burned in the engine. With that extra fuel going into the engine, the computer expects to see a corresponding change in the exhaust gas that leaves the engine. There can also be other strategies it uses to verify those fumes are flowing from the canister. In this case the computer isn't seeing the results it expects to see when it opens the purge valve. That would make sense because the second code indicates that circuit is shorted.
There's about a 50 percent chance the solenoid that opens the valve is shorted, but before we spend your money on parts, we have to check the wiring and connector terminals for problems. I don't know what boot your mechanic is referring to, but that is not the type of thing that can be monitored by the Engine Computer. The computer can only detect electrical things, meaning the results that show up and are detected by sensors as a result of those other things. In the case of a fuel vapor hose that has developed a leak, that would allow fumes to escape, so there is a way to detect that, set a diagnostic fault code, and since it adversely affects emissions, it turns on the Check Engine light. The fault codes are for a "small leak detected", or "gross leak detected". Since those codes haven't been set, don't worry about that system yet.
Where this can become confusing is when a problem is detected, as happened here, the computer knows some of the other tests it runs can't be expected to give the proper results, so it suspends those tests. Once repairs are made, the suspended tests resume, and if another problem is detected, that is when the next fault code will be set, and the Check Engine light turns right back on again. This is frustrating for mechanics because they have to start the diagnosis all over again, and tell you more parts or services are needed, (we really hate having to do that), and it's frustrating for car owners because you incorrectly think the problem wasn't diagnosed correctly or repaired properly. Most of this frustration can be avoided by having the problem corrected as soon as possible. When people wait many months, that leaves a lot of time for another problem to develop that may or may not be related.
Saturday, October 19th, 2019 AT 8:40 PM