Another Code 31 Problem

[tg2025]

Hey Everyone-

I've had my TJ for about 2 years– '97 4.0 w/ 90k miles on it.

It started throwing code 31 about a year and a half ago. First, replace the purge solenoid and gas cap. CEL went away for about a month. CEL back on, so I then replaced the charcoal canister (Duralast VC120 Vapor Canister) and cleaned out any charcoal from the lines. CEL went away for about a month... then CEL came back. Had Auto Zone do a scan- apparently the purge solenoid had gone bad again. So I replaced it again (PV300 Duralast Purge Valve/Solenoid.) CEL is back!

I've done a visual inspection of all the wiring and tubing and there are no leaks or cracks- on the new canister, I even clamped the hose connections to the aftermarket canister.

I'm about to lose my mind- any ideas? I'm in CA and have a smog inspection coming up so gotta get this fixed! Any and all ideas would be greatly appreciated!

 

[TJ Jim]

Are you referring to p0031?
https://www.engine-codes.com/p0031_jeep.html

 

[tg2025]

Are you referring to p0031?
https://www.engine-codes.com/p0031_jeep.html

Sorry-P0441.

 

[TJ Jim]

Lottsa tubing on top of the gas tank, at least on my 04. Guess I’d start with a smoke test to try and locate a leak in all the plumbing.

 

[macleanflood]

I bought a smoke tester on Amazon for $60.

Double check you solenoid valve is clicking after the engine warms up.

And a pic of how you hooked up the canister might be good...you sure you got all the lines in the right spot?

I recall when I did mine one of the inlets was a touch big...I slipped a 1/2" piece of 1/4" silicone fuel line plus the evap hose to tighten things up.

-Mac

 

[tg2025]

Hey Everyone-

Update:

Took the advice here and brought it to a shop to have them smoke the lines. There is no smoke leaking out, which is good news.

Bad news is that they think it's a power problem. We couldn't find any bad wiring, and there seems to be voltage getting to the solenoid. We replaced the fuse behind the glove box just to be safe, and the next step is to swap the current Durlast purge valve for a mopar one- maybe the Jeep is finicky about the aftermarket product?

I'm crossing my fingers that this does it, but I'll keep the thread updated if the CEL comes back after this!

 

[tg2025]

Update for anyone in the future who might need the info:

Brought it to the shop and after swapping purge selenoid and evap can with OEM parts, the CEL came on and stayed on- even after hard resetting the battery. We triple-checked all wiring, did another smoke test: everything was good. So, without any other options, we ordered a new PCM from Wranglerfix and swapped it. Two months later, and the CEL still hasn't come back on (yet!)! No idea what was happening, but the car passed CA emissions, drives better (I really can't believe how much smoother that computer makes the car drive), and there is better pressure in the lines thanks to the OEM parts.

So, did I spend too much money? Hell yea. Is it fixed and the car better than ever? Hell yea.

Hopefully this helps someone in the future, and thanks to all the commenters in this thread for the help!