2001 Ram 1500 5.9L 4x4

I'm getting a P0455 error (EVAP Emission Control System Leak(Large)). I replaced the gas cap with a new one from Dodge and checked the vac hoses hoses on the passenger side fender. The hoses look OK, from what I can see.

What should I check or replace next?

Thanks,
Mike

 

Mike,

This system is comprised of a EVAP Canister under the driver side door. It's round, it's black and, about 8 inches long and maybe six inches in diameter. There's two lines that run from it. Check the larger boot for cracks or leaks at the canister first. Usually, if there's a leaker, it's due to dry rot on that boot area. The line ends up pulling out from the boot and creates a gross leak.

Upstream from that is a line that runs from that up to what is called the PURGE SOLENOID. This solenoid is actually an electro-mechanical pump that uses a solenoid actuated diaphragm to move the vapors into the charcoal canister.

If that diaphragm has jammed or, has a significant tear, it will leak.

Cheap and dirty test: place one end of a prybar on the body of the purge solenoid while placing the handle up to your ear. If you hear a clicking sound, it's moving at least and, it's not jammed. However, it still may be leaking.

Now, I forgot to tell you where this component is located on the vehicle. It is mounted off the driver side fuel rail in the rear part of the intake. It is black, has two VAC lines coming from it and, has one, two wire connector attached to it at the top.

NOTE: if you remove this component, make sure to NOT FLIP it upside down thus reversing the VAC lines possibly jamming the diaphragm. The CEL will definitely illuminate when this is done by the way.

That makes up the entire EVAP system. So, if there's a leak, it is going to be the lines or, the solenoid assembly or, the EVAP canister under the truck.

Hope that helps.

Oh, one more thing: if all the lines and canister check out fine, the most likely root cause is a leaky solenoid assembly to which, you'll need to obtain a new one as they are not user / field serviceable. To check for leaks at the solenoid level, you can try pulling vac on it to see if it holds or not. If it doesn't, the diaphragm is either stuck open or torn. I believe the ports are labeled too so, you'll see which one to connect VAC too. It's been quite a while since I worked on that system but, if memory serves me correct, I believe you can test it by pulling vac on it.

CM

 

here's some things to check with some pictures.
i've replaced some hoses and cut an inch of the ends of several more, but still haven't solved mine.

https://dodgeforum.com/forum/2nd-gen...-leak-fix.html

 

Thanks, CM! I think you nailed it! There was a split hose at the EVAP canister - the shorter, rear fuel line that pushes on and goes through the frame. Just the end was split, so I trimmed the hose and put it back on.

I was able to see it with a flash light and mirror, too, so I didn't have to remove the canister.

dhvaughan, thanks for the link! The pics were helpful.

 

I disconnected the battery, so the light is off now, but I was reading about the drive cycle. How does that work? If the light is going to come back on, it'll be within a certain number of miles or warm-ups and cool downs? Little confused on this.

 

Not certain if this is a common fix, but it might help!

 

mine always comes back on 2 days after a pcm reset, and its always at the same place, about 3 miles from the house while on the way to work.