2002 Taco throwing code PO440

Taco Man

Taco Man

Well-Known Member
Hi again everyone! The check engine light came on on my 2002 base model Taco 2.4l this morning on my way to work. When I got home I connected my scanner to the diagnostic port and pulled up the codes, the only code it threw was PO440 for the evap emissions system. I'm thinking it might be a bad gas cap. My question is is there a way I can test the gas cap? I know most shops have a gas cap tester that pressure test them. Maybe I can have my mechanic test it. Should I just buy a new one and put it on then clear the codes and see if the check engine light comes on again?
 
Taco Man said:
Hi again everyone! The check engine light came on on my 2002 base model Taco 2.4l this morning on my way to work. When I got home I connected my scanner to the diagnostic port and pulled up the codes, the only code it threw was PO440 for the evap emissions system. I'm thinking it might be a bad gas cap. My question is is there a way I can test the gas cap? I know most shops have a gas cap tester that pressure test them. Maybe I can have my mechanic test it. Should I just buy a new one and put it on then clear the codes and see if the check engine light comes on again?
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Just an update folks I just now went ahead and replaced the gas cap and deleted the codes. I'll drive it the next few days and see if the check engine light illuminates again. I will update y'all in a few days one way or the other. Hopefully this fixes the problem.
 
Hey folks just wanna update y'all! I've been driving the truck since Sunday and I've been checking the readiness status everyday since, it keeps showing one not ready. Of course the one not ready appears to be the evap system! Ugh! Will continue to update the next couple days or so.
 
Well I plugged in the scanner a little bit ago and it's still showing one not ready for the evap monitor. I read on the internet somewhere that the fuel tank has to be between 1/4 and 3/4 full for the ecu to test the evap system. Well it had a 1/2 tank of gas in it and I drove it to the gas station and filled it up Sunday because I generally don't like to let it drop below a 1/2 tank before I fill up because of the cost of gas these days. If I had known that I would've held off a day or so before I filled up. Oh well lesson learned I guess!
 
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Yippee! I just now plugged in the scanner and all monitors are showing ready! FINALLY!!! Lol! So folks any time you get a PO440 code check your gas cap! I read on the internet that this particular code is often accompanied by another code however one Toyota Tacoma site I looked at said if it's the only code present a faulty or leaking gas cap is one of the most common causes. They also mentioned the purge solenoid and charcoal canister as a possible cause as well but could be any one of many problems. In my case PO440 was the only code present which is why I decided to go ahead and replace the gas cap, it's nearly 20 years old and has 142,9xx miles on it and a new one is only 10-15 bucks!

Here in Texas you can pass inspection with one not ready however I wanted to verify the problem was fixed. Here it has to pass inspection within 90 days before getting your registration sticker which mine expires in February so I have a little time. Anyway I just wanted to update y'all and pass this information on to people, it may help someone else in the future.
 
Just as a general rule when you get a general evap code the first thing to check is the gas cap, very inexpensive to replace and if that doesn't work you're not out that much. If that doesn't fix it the best thing to do is go to a garage and get a smoke test done, looking for any leaks. I got an EVAP code on my old F150 because a squirrel had chewed a hole in the line than ran from the top of the tank to the vent tube. Took me forever to find it but less than $5 to fix.
 
TacoTruck2019 said:
Just as a general rule when you get a general evap code the first thing to check is the gas cap, very inexpensive to replace and if that doesn't work you're not out that much. If that doesn't fix it the best thing to do is go to a garage and get a smoke test done, looking for any leaks. I got an EVAP code on my old F150 because a squirrel had chewed a hole in the line than ran from the top of the tank to the vent tube. Took me forever to find it but less than $5 to fix.
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Yup! I've learned that myself! I decided to go ahead and replace the gas cap because the truck is damn near 20 years old and it had the original gas cap. I knew a new one is only about 10-15 bucks so it was worth going ahead and replacing it and see what happens. After doing that and clearing the codes problem fixed!
 
Just wanna add something to what I said before. It's always best to check the simplest things first, then move to the more complicated things. I've learned the simplest things can trigger a code and illuminate the check engine light.
 
I know it's been close to a month since I originally posted this thread however I would like to add something. I noticed every time I fill up the new gas cap is really tight coming off! I have to apply quite a bit more pressure to unscrew it, not like a freaking gorilla or anything but just takes a bit more pressure!
 
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