Just like last time, C1201 - P0441 - P0455 codes returned. I suspected they may, because the gas cap has felt loose for the last couple of months. OEM Toyota gas cap.

As I understand it, the evap system is pressure tested when the 4R sits idle for at least five hours, and then a pressure pump or a vacuum pump is activated for a system test.

I'm wondering if anyone here knows where the pump is located, and what would happen if I disable the pump by disconnecting its electrical supply?

Would my 4R go on with life with an imperfect gas cap, or would I get the mother of all CELs?

hope its your gas cap and i know that does often resolve evap codes.

sorry to hear about this though, i had a 'small evap leak' code on my wrx and without doing a smoke test and even when doing them the evap leaks can be pesky i heard... so much so that i actually sold the car with the evap code as is, to a 15 year old potential or future gangster (technically sold to his 32 year old smokeshow madre). kid got a 2005 wrx, stock car with 90,000 miles for 5 grand. i didnt even try the gas cap i was so over that fn car. got it with 38k miles and in less than a year timing belt broke while driving (seized water pump) and i had to cut a $3 grand check for all new valves.

to your ending question, i was told that a small evap leak is also pesky in a sense it could be 500 things and also more than likely run perfectly fine.

Do you “top off”, when fueling up?

That's a good one, so many people don't know that they trashing charcoal canister by overfilling gas.

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Yeah, and that causes lots of evap issues. Don’t top off!

OEM gas cap is $12 on Amazon. Buy a new one.

In less than 2 years i went through 2 non oem gas caps and 1 toyota gas cap...now im fed up and going to try just replacing the rubber gaskets on the toyota gas caps.

Not sure if it has to do with the cold Chicago climate and the gas cap gaskets drying up?

But this never happened to me while i was in Dallas for 2 years.

2008 w/ 147k

No, I don't top off.

Where did you find the gasket in the cap? I looked and didn't see anything like a rubber o-ring. I did see a sealing surface that appears to be a flat plastic material.

Just buy a new gas cap. I had to a few years ago and bought a Stant replacement cap. You'll never pass smog test if you modify/disable any of the emission systems.

I just looked at my gas cap and it does indeed have an O-ring on the plastic center section just past the threaded portion fitted into a groove, It appears to be the original cap but not sure if it is, I have never replaced it and it looks old.

Sometimes a light coating of grease on the o-ring will help it seal better.

That will also help diagnose the leak, if the cap is sealed then you know to look elsewhere. There was a thread here about failed hoses and connectors over the gas tank. They had rotted away.

I use the same silicone grease that I use on the brake pad pins.