Chosen Solution
I have a 1999 Corolla, 226,000, 1.8L automatic. Check engine light came on recently indicating p0441 & through a second OBD reading (I was curious) at a different store indicated p0441 AND p0446. I bought a new gas cap as I suspect it was overdue (could smell gas). Suggested replacement for the p0441 code from one auto discount chain said likely solution is “replace Vacuum Switching Valve (VSV). I recently replaced my front end brakes (drums, rotors, calipers) and purchased 2 new tires - seemed reasonable (yet big ticket item) and fit my cars replacement timeline for these repairs. I intend to change out PCV valve as it’s probably overdue too. My question is how can I, if possible, begin to trouble-shoot this issue on my own? The car is going into the mechanics (reliable) in about a week. My concern is that this possible fix (via the mechanic) could be pricey (charcoal canister, etc.). Also, I don’t fill up the tank (about 3/4) due to leak when filled to tippy top. My mechanic is aware of this and has said 3/4 tank (max) is fine. I suspect that this may be the definite beginning of the end for this car. If those codes had popped up prior to my brakes having been replaced, I think I would have nixed the whole thing and junked the car. Any feedback would be much appreciated. Thanks.
Based on your full description, I believe your check engine codes are directly related to the gas leak that occurs when filling the tank. There is a leak somewhere in the gas tank towards the top or something connected to it that when addressed will likely solve the issue. The fuel tank is supposed to be pressurized which is why we start with a faulty gas cap as it is the easiest and cheapest to change. If the leak is bad enough that gas can come out or you smell gas, then there is no way the tank can maintain proper pressure. Code P0441 means the EVAP system is not able to do its job in preventing fuel vapors to escape into the atmosphere. There may be other issues compounding, but as long as the vehicle runs okay, I would only address the gas leak and then address the engine codes one by one at a later date.
