Gas cap and check engine light

Hey all,
2017 Tacoma Sport with 100,000 plus miles. Last month check engine/trac off lights. Went to local auto parts place and had them check the code and it was the gas cap code. Bought a replacement from Amazon, reset code (disconnected battery cable a few minutes) and was good for a few days. Light back on, same code, so the following week went to Toyota and bought a genuine replacement cap. Installed new cap, reset again, all good for a few days, light back on.
What do I need to check in relation to the fuel cap venting? Is there a hose possibly clogged or that I can replace? I could live with just the lights on, but it also disables my cruise control and that’s a pain… LOL….

 

Do you always top off your tank when you fill up?

 

yes, but I don’t force any extra… and never had an issue for almost 100,000 miles…..

 

https://youtu.be/jPiiqcDxDxY?si=RVvW1SDec20TwF4F

 

There is no gas cap code. There are a few evap system leak and/or performance codes. You guessed at a gas cap, and that’s obviously not it. A competent shop will have to smoke test the evap system to find the leak.
I’m assuming you had a P0456?

 

You have an evap system issue…….it’s not the cap

 

Before you completely rule out the gas cap, check out post #61 on this link. Mine looks like the gas cap on the left and no CEL light in 8 years. If the inside of your cap looks like the one on the right that could be throwing the codes.

https://www.tacomaworld.com/threads/locking-gas-cap.750710/page-4

 

Replacement cap was bought directly from the Toyota dealership parts department by me. Looks like the one on the left in the photo…..

 

I didn’t “guess” gas cap, I was told that’s what it was from the guy who checked the codes. He didn’t show me the code but said the number and I cannot recall what he said for sure because I was relieved it wasn’t something else. I don’t have much disposable income, so, since it’s “obvious “ to me there’s something else other than the cap, that’s why I asked what else could I look for or check myself to try and solve this issue.

 

Sorry, whoever scanned the code guessed gas cap. Evap codes require a specific diagnosis procedure, typically involving a smoke machine and tech stream. Without those diag tools it’s really anyone’s guess.

 

My gas cap clicker broke so I bought new cap from eBay, not exactly same as stock. Threw a code after few days. Cleared code and put old cap back on, no issues. So I bought replacement OEM cap and it worked. Might be a bit finicky trying something else. Sorry, I don’t remember the specific code.

 

I've been advised to never top off the gas. There's something that can be contaminated by doing that. Search this forum for that info.

 

It can backfill down into the charcoal canister. I know a ton of people do it but I have no idea what that extra .37 in gas is going to get them. I believe it’s an OCD thing.

 

When you pay cash, it's easier to round up to the next whole dollar.

 

Easy for round numbers; hard when you pay >$100 an hour for a mechanic’s time.

 

Which sort of makes sense and sort of doesn’t. If you go to the store and buy whatever, do you tell the cashier to just round it to the nearest whole dollar? Probably not.

 

Guilty. Totally OCD. I like to pay in round numbers. (Doesn’t help that my truck’s range is smaller than I’d like.)

 

Yeah I get that if you pay cash to have even dollars but man if you mess up the evap system then that $0.43 of extra gas you pump in every fill up just cost you a lot!
I literally stopped doing that years ago and sure don't want to do it to my truck. This is the only vehicle I've ever had since brand new so I'm trying to do my best to care for it correctly. When the pump clicks off I'm good. Besides who pays cash for gas nowadays? Most people get paid by direct deposit and use a debit card or something unless you work a job where you get cash tips.

 

I went in for an emissions test at a place that just does testing. The truck failed. I was told, "go buy a gas cap and come back, it'll pass". He told me it threw some evap code and he sees it frequently when the gas cap is bad. I can't say what he code he saw saw but he nailed it. Bought a cap, passed emission and the problem hasn't come back since, (about 6 years). My point is the cap may not be your issue but it's not like you were way off base, it could have easily been the cap and according to someone who tests these for a living, it often is.

 

The cap is the cheapest, easiest thing to try and is often the issue. Plus usually the customer can install it themselves. So of course it makes sense to try a new cap first and eliminate that.