[kiwi29]

Just the other day I had an error code that sent a CEL on active, I scanned the code with an OBD2 reset/scan tool and it said code P0440. When I looked it up in the manual, it said malfunction with the evaporate emissions system. My question is what could that be? Is it major or could it have been a gas cap malfunction? I was able to reset the code and erase it and it never reappeared. (Its been about 1 week) I just wanted to make sure that nothing was wrong with it. Any help will be greatly appreciated!

[josephbet01]

There's an electric pump that pressure tests the system for leaks whenever the car "wakes up". You may hear it cycle quickly when you open the door first thing in the morning.

I believe I posted a pic of this pump at one point. It's located inside the passenger side rear wheel well under the plastic shield. Its called a DTML Pump. Worth about $100 and takes about an hour start to finish. Easy job.

http://www.e90post.com/forums/showthread.php?t=260065


If its not a loose gas cap this would be my bet.

[kiwi29]

Originally Posted by josephbet01

There's an electric pump that pressure tests the system for leaks whenever the car "wakes up". You may hear it cycle quickly when you open the door first thing in the morning.

I believe I posted a pic of this pump at one point. It's located inside the passenger side rear wheel well under the plastic shield. Its called a DTML Pump. Worth about $100 and takes about an hour start to finish. Easy job.

http://www.e90post.com/forums/showthread.php?t=260065


If its not a loose gas cap this would be my bet.

Thank you, but do you think that this would send an emissions code?

[josephbet01]

If it fails? Of course. There are a few threads here where people have seen them fail. It throws a check engine light.

[1QuikWS6]

Sometimes that code is thrown for the simple fact that the gas cap has not been put back on correctly as you surmised.

Take off cap, put back on and give it a couple 'clicks' see if the problem goes away. It could also be that the cap is bad & needs replaced.

I always start with the least expensive/involved items on the diagnostic tree before moving on to the more $$

[kiwi29]

Originally Posted by josephbet01

If it fails? Of course. There are a few threads here where people have seen them fail. It throws a check engine light.

That's actually pretty weird though? But thanks, ill look into it this weekend

Originally Posted by 1QuikWS6

Sometimes that code is thrown for the simple fact that the gas cap has not been put back on correctly as you surmised.

Take off cap, put back on and give it a couple 'clicks' see if the problem goes away. It could also be that the cap is bad & needs replaced.

I always start with the least expensive/involved items on the diagnostic tree before moving on to the more $$

I think it was the gas cap? But the thing is, I filled up the tank about 5 days prior to the problem and haven't touched it since? any clue why it'd go off? Do our gas caps untighted themselves ?! O.o

[pinoye90]

I had the same problem and ppl kept saying its the gas cap but when I replaced it the light when back on after 10min of driving. Then after researching more I found out it was the vapor sensor which is common to going out on bmw's. I did a DIY on this forum on how to replace it. Cost can be about 200+ at the dealer to diagnose. I'm pretty sure that's what's throwing the code.