CEL for EVAP

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Just curious on this because i've heard this so many times and i think its the #1 seller of gas caps.

Say you have a CEL for evap, how often has the actual fix be a gas cap? I hear it all the time when i'm in the parts store or from non-car friends.



Honestly, about 2 out of 15 times i've looked at a car has it been actual gas cap. And of those 2 times, it literally was user error. Owners did not fully tighten the gas cap or somehow cross threaded it. The other times i want to say, about 10 were evap purge valve or solenoids. And lastly were just vac or fuel lines. Maybe it just my luck and what i've seen.

BTW, i really hate those type of CEL because the DIY like myself doesn't have a need for a smoke machine or a scanner that can activate the evap sensors.
 
It's the cheapest fix before bringing it in to a competent mechanic for a diagnosis. If you check out Eric's diagnostic videos on his SMA Youtube channel he doesn't just throw on a gas cap for a P0456 or other evap code. It's watching videos like that makes me want to step up my game in diagnosing issues and not just throw parts and hopefully the code stays away after clearing the codes.
 
I'm dealing with a P0442 code right now on our Mazda 5. Replaced the gas cap first because it was only $8, so why not try it? It was not the gas cap.
 
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On My Ram 1500, found out that the P0465 was happening because I would pump in more gas after the pump kicked off. I stopped doing that after seeing that solution on the Ram Forum and now no more clearing codes.
 
Originally Posted By: bowlofturtle

Say you have a CEL for evap, how often has the actual fix be a gas cap?


Almost never. In 15 years and hundreds and hundreds of fixing evap leaks, only once have I seen a bad gas cap.
 
Originally Posted By: NateDN10
I'm dealing with a P0442 code right now on our Mazda 5. Replaced the gas cap first because it was only $8, so why not try it? It was not the gas cap.


Now you have a spare gas cap . :-(
 
I've had a recurring EVAP code in a Honda that was caused by a bad gas cap. The ratcheting mechanism became weak with age and didn't allow the cap to be properly 'torqued' so to speak.

Never changed the cap, I just squeezed the sides of the cap real tight while reinstalling the cap to bypass the ratchet mechanism. Never had the code again lol.
 
I've had the evap code throw on 3 cars. Once it was the gas cap. The gasket had hardened. Other time it was the cannister. Replaced that and all fixed. Still dealing with the code on the 3rd vehicle. New gas cap didn't fix it.

Going to reset the CEL and see if it stays off.
 
I have a P0452 code pop up about twice a year; always during hot weather. The code clears itself after a few ignition cycles.
 
I've seen rust on the gas cap sealing surface on my Accent. Some sand paper and clear coat fixed that.
 
P0452 on my '01 Silverado turned out to be chewed wiring for the fuel tank pressure sensor.

I already had a spare gas cap, the original, replaced with a lockable one after three years, and that didn't fix it. I was going to change the sensor, and the whole harness came off when I unhooked the plug.
 
Gas caps don't fail as often as hoses, tubes, vacuum lines, purge valves, vent valves, etc.

I still sell a lot because that's what people want to try first. If they ask about CELs, I explain why it may not fix their problem and they generally understand, then come back for a vent valve kit later.

I've done it myself. My truck has a "check fuel cap" light that came on a few years ago. It didn't throw a CEL, just the check cap light, but it was an indicator of a sudden, large EVAP leak. I checked fuel cap, and even replaced fuel cap, but nothing. Finally I looked under the hood, and somehow one of the purge valve lines had come loose. I plugged it back up and the light turned off immediately.
 
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