06 Rubicon P0456 evap code

[AndyG]

Who has dealt with this ? My purge solenoid is closed with engine off, no line leaks , replaced fuel cap with a Stant.

I can't find what is triggering this code, runs great.


Your Pal,
AndyG

 

[Chris]

Usually it's one of the following:

• Loose or damaged gas cap
• Leaking or disconnected EVAP hose
• Faulty purge volume control valve
• Faulty canister vent control valve
• Charcoal canister leak
• Leaking fuel tank

This is a perfect time for a smoke test. Run some smoke through the system and see where it leaks out. Often times these leaks are hard to find, and the smoke test is a great way to find said leak.

 

[John Scoggins]

Small EVAP leaks are sometimes a pain the butt to find. Before I got a cheap smoker from Amazon I found my first leak by blowing in the EVAP system from the rubber hose under the drivers footwell toward the tank. To do this (or to smoke that line for that matter) you have to plug the vent line from the Charcoal Canister, then remove the rubber line from the engine side (check that line, it might be the leak) and blow. Had a friend pluging the charcoal canister vent and he heard the leak, it turned out to be a very small rotted spot in one of the canister hoses.
Since then I have used my smoker to find a few others as they have cropped up.

 

[Rubicon John]

I would do as suggested and smoke test the system if possible. If you can’t find a leak, it’s quite possible the leak detection pump is going bad. I speak from experience on non Mopar vehicles, but I’ve seen many pumps over the years cause leak codes to be set.

The purpose of the pump is to activate itself and measure the amount of amperage it takes to pressurize the fuel system. If the pump requires a low amount of amperage and runs for a long time (below a given threshold), then it tells the PCM that there is a leak in the evap system.

If the pump begins to go bad, it can send the PCM erroneous readings indicating a leak that isn’t actually there. Start with the smoke test of course.

 

[AndyG]

I would do as suggested and smoke test the system if possible. If you can’t find a leak, it’s quite possible the leak detection pump is going bad. I speak from experience on non Mopar vehicles, but I’ve seen many pumps over the years cause leak codes to be set.

The purpose of the pump is to activate itself and measure the amount of amperage it takes to pressurize the fuel system. If the pump requires a low amount of amperage and runs for a long time (below a given threshold), then it tells the PCM that there is a leak in the evap system.

If the pump begins to go bad, it can send the PCM erroneous readings indicating a leak that isn’t actually there. Start with the smoke test of course.

Where is the actual pump?

 

[AndyG]

Usually it's one of the following:

• Loose or damaged gas cap
• Leaking or disconnected EVAP hose
• Faulty purge volume control valve
• Faulty canister vent control valve
• Charcoal canister leak
• Leaking fuel tank

This is a perfect time for a smoke test. Run some smoke through the system and see where it leaks out. Often times these leaks are hard to find, and the smoke test is a great way to find said leak.

I'm making me a pump (I think ) or getting allow cost one ..it's gotta be minor or several real small...

I clamped one line , and that helped it go waaay longer without a code, then I hair sprayed the connections to seal them ... Will smoke test if she codes again....

 

[Rubicon John]

Where is the actual pump?

If I’m not mistaken, it’s in the fender well behind the passengers side tail light. I had to move the carbon canister assembly out of the way when I installed my tail lights, and it’s typically mounted with the canister.

There’s a corrugated type hose running to the fuel tank from there too. I wouldn’t be surprised if it were prone to getting brittle.

 

[Bigfoot-NM]

I am dealing with it right now as well. I've replaced the gas cap twice now. I've smoke tested it on three separate occasions and cannot find a leak. I have checked and rechecked the evap lines all the way back from the engine to the fuel tank and up to the evap canister more times than I can remember.

Just a couple of other things to note on this. The system won't run the evap pressure test unless the fuel tank is between 3/4 and 1/4 full. I can reset the P0456 code on mine and the only time it comes on is when the tank gets below 1/2 tank, closer to 1/4 tank.

Just this past weekend, I replaced the Leak Detection Pump. Not driving the Jeep much because of In Place orders for Covid so it may be a while before I actually know if this fixed it or not.

The evap canister and leak detection pump are located in the rear passenger wheel well behind the tire. If you still have the plastic wheel well liners installed, you will have to remove it. Then there is a metal plate partially covering the evap canister that has two bolts and one nut. There is also one bolt on the bottom of the evap canister housing you have to loosen to get the canister assembly out. And one plastic line coming from the gas tank. Not sure what size tires you are running, but it's best to remove the left rear tire to access all of this.

Keep us posted.

 

[KCsTJ]

I purchased a hand transfer pump from HF. It's made for use with fluids but I stuck a lit cigar in one end and it became a smoke machine, for about $12.00.
Here's a pic

, I used this to find a vacuum leak, also can be used to find purge leaks

 

[John Scoggins]

The one piece that cannot be tested UNLESS you activate the Leak Detection Pump is the vent valve in the pump. I have attached the EVAP section of the manual for reference.

The purpose of the pump is to activate itself and measure the amount of amperage it takes to pressurize the fuel system.

On the TJ's the pump is a vacuum operated diaphragm pump with a reed switch on the diaphragm. The system uses the reed switch on the diaphragm and time (along with a spring on the back side of the diaphragm) to determine if there are any leaks. The Leak Detection Pump does us an electrical solenoid to operate the diaphragm but that will give a different code if the solenoid is bad.

 

[Rubicon John]

On the TJ's the pump is a vacuum operated diaphragm pump with a reed switch on the diaphragm. The system uses the reed switch on the diaphragm and time (along with a spring on the back side of the diaphragm) to determine if there are any leaks. The Leak Detection Pump does us an electrical solenoid to operate the diaphragm but that will give a different code if the solenoid is bad.

Interesting, I did not realize it operated differently than the pumps I have familiarity with. I’d certainly think the reed switch could fail or be making poor contact to cause an erroneous leak code but that’s just a theory.

I also wonder if the diaphragm could develop a tear and fail a leak test that way.

 

[AndyG]

Thank you... a very pervasive view like you guys have done was exactly what I was after... Great job

 

[AndyG]

I purchased a hand transfer pump from HF. It's made for use with fluids but I stuck a lit cigar in one end and it became a smoke machine, for about $12.00.
Here's a picView attachment 149536, I used this to find a vacuum leak, also can be used to find purge leaks

I think I saw something like that at a party one time....

 

[John Scoggins]

Interesting, I did not realize it operated differently than the pumps I have familiarity with. I’d certainly think the reed switch could fail or be making poor contact to cause an erroneous leak code but that’s just a theory.

I also wonder if the diaphragm could develop a tear and fail a leak test that way.

Those seem like a real possibility,

A tear in the diaphragm will probably set a LDP code since it will not be able to pump

 

[XtremeJoe]

I am dealing with it right now as well. I've replaced the gas cap twice now. I've smoke tested it on three separate occasions and cannot find a leak. I have checked and rechecked the evap lines all the way back from the engine to the fuel tank and up to the evap canister more times than I can remember.

Just a couple of other things to note on this. The system won't run the evap pressure test unless the fuel tank is between 3/4 and 1/4 full. I can reset the P0456 code on mine and the only time it comes on is when the tank gets below 1/2 tank, closer to 1/4 tank.

Just this past weekend, I replaced the Leak Detection Pump. Not driving the Jeep much because of In Place orders for Covid so it may be a while before I actually know if this fixed it or not.

The evap canister and leak detection pump are located in the rear passenger wheel well behind the tire. If you still have the plastic wheel well liners installed, you will have to remove it. Then there is a metal plate partially covering the evap canister that has two bolts and one nut. There is also one bolt on the bottom of the evap canister housing you have to loosen to get the canister assembly out. And one plastic line coming from the gas tank. Not sure what size tires you are running, but it's best to remove the left rear tire to access all of this.

Keep us posted.

Did you end up getting this solved. I just popped the code and ran a smoke test, but no leaks, so wondering if its the pump?

 

[Sgt Jarhead]

Did you end up getting this solved. I just popped the code and ran a smoke test, but no leaks, so wondering if its the pump?

I’ve searched the internet regarding the same code for my 06’ and my leak ended up being in a very different area. The leak came from a soft line that connects to the hard line beside the fuel tank under the rear driver side tire behind the plastic rear well. I couldn’t see any smoke though could hear an air leak coming from the area. I moved the soft line partially and that’s when the smoke started coming out between the connection. I ended up cleaning the hardline and taking a ring worm clamp to both lines and the code hasn’t come back since.

Just thought I’d throw this in here for another place to look.

 

[Bigfoot-NM]

Did you end up getting this solved. I just popped the code and ran a smoke test, but no leaks, so wondering if its the pump?

In my case it was the leak detection pump. Everything has been working fine since I replaced it.

 

[Undercover]

I’m replacing the canister and the leak detection pump and that thing under the hood. I’ll be dammed if this doesn’t fix that f-ing P0456 code. Replaced the fuel pump already which was the only smoke the smoke machine produced according to the folks at the garage who did the first diagnosis. Got the code to stay off for a while and now it’s back. Good on this thread for convincing me to due the pump. I’ll report back once the code clears and doesn’t return.