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po456 evap small leak 2011 Ram

Discussion in 'Repairs, Maintenance, Help' started by mopar56, Feb 4, 2016.

  1. mopar56

    mopar56 Active Member

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    this code was just thrown on my way home tonight, Scanner says evap, small leak?, any common places to look?, I did a quick little search and possible causes are loose or faulty gas cap, well it wasn't loose, or cracked hose at evap canister, seems unlikely as we live in a moist climate so it wouldn't dry out, anyway has anyone experienced this on there Ram, it has the 5.7 Hemi with 85km's on it
     
  2. Int

    Int Active Member

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    It was a corroded filler tube on my Intrepid. A mechanic warned me about that well in advance so I knew what to expect when I got p0455, p0456, etc. A leak by the fuel tank would probably show on the driveway.
     
  3. AllanC

    AllanC Well-Known Member

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    Before randomly throwing parts at the problem, I would seal the fuel cap on the vehicle. Make sure you have about 3/4 tank full of fuel. Make sure fuel cap is properly tightened. Take a heavy, 1 quart or 2 quart vinyl bag used for food storage and place it over the fuel cap. Seal the bag to the exposed filler neck with several wraps of duct tape. Drive the vehicle for several days. If the check engine lamp turns off then the fuel cap had a small leak and your vinyl bag installation effectively sealed the filler neck. If the check engine lamps remains illuminated, then you know the fuel cap is not the issue and you have not spent money needlessly trying to solve the problem.

    If the check engine lamp is still glowing with code P0456 present in the PCM (powertrain control module), check the hoses going to the evaporative canister. They should be tight and not brittle / split at the connecting points.

    I believe the vapor canister has an evaporative system monitor (ESM) attached to it. The ESM has a plastic tube that plugs into a grommet on the vapor canister along with an electrical connector. The ESM has internal weights which require it to be oriented correctly so gravity effects its operation properly. You can remove the ESM from the canister, make sure the attaching grommet is clean and still pliable with no splits or cracks. Apply a thin film of RTV sealant to the grommet and reattach the ESM to the canister. If there was a small leak at the grommet, the RTV sealant should fix that situation. Drive the vehicle for a few days and determine if the check engine lamp and code P0456 disappear.

    If P0456 code is still present and the check engine lamp still illuminated, it is possible that the contact points in the internal switch in the ESM are corroded or have carbon which is preventing a closed circuit. This internal switch must close and pass a small electrical current within a specified time frame as part of the emissions test. At this point the ESM would need to be replaced.
     
  4. ImperialCrown

    Level III Supporter

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    It only takes a pinhole (.010"/.25 mm) to set a small leak code. Small leaks can be more difficult to find than medium or large leaks which may be actually visible and more obvious.
    The rubber evap hoses, particularly at the ends can crack, shrink and dry rot after a number of years. It has nothing to do with ambient moisture. A 5 year old truck shouldn't have bad hoses yet as rubber quality has improved, but bad batches can get through once in a while. Hydrocarbon vapors can deteriorate rubber over time. The plastic vapor lines usually stay good unless they have been hit or damaged.
    Hydrocarbon fumes can also harm some RTVs. If you do seal with RTV, use a grade that can stand up to fuel (hydrocarbons).
    The Caliber threw a P0456 once and it turned out to be the filler tube end where the gas cap rubber seal seated against. The sealing surface was rough from gas nozzle bumping and surface rust. Light sanding and a smear of grease on the rim of the filler tube end fixed the cap-to-tube seal and the light has stayed out.
    At the dealer, we have the 'smoke machine' which fills the evaporative system with a cool vegetable oil smoke laced with a florescent dye that leaves behind a residue and the glow shows up under a black (UV) light. It injects the smoke at low pressure to fill the system. We use the smoke test after a visual inspection is inconclusive.
    The PCM tests the 'closed' evaporative system integrity with the NVLD (natural vacuum leak detection) switch or ESIM (evaporative system intefrity module). There is no more active LDP (leak detection pump).
    NVLD is nice and simple as it uses the natural warming and cooling (expansion and contraction) of the vapors in the closed system to actuate a detector switch. If there is a leak or the system is somehow venting, then a pressure change will never happen to trip the switch and a fault code will set.
    The switch itself can fail, but any leaks must be ruled out first.
     
  5. chuzz

    chuzz Well-Known Member

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    Try just cleaning the cap and filler neck and the area around it. Check the gasket or O-ring seal on the cap too. Make sure it's not cracked or torn. And make sure when you put the gas cap back on, that you hear it click a couple of times. That way, you KNOW it's tight.
     
  6. 1999 White C5 Coupe

    1999 White C5 Coupe Well-Known Member

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    I had this code with my 2003 Dodge Durango 5.9 4x4 (some time ago...). I checked all the vacuum lines although at the time, the vehicle was not that old (purchased new). I found a vacuum line with a crack / split at the end where it attached to a metal nipple on the throttle body. There was some slack in the line, so I cut off the end about one-inch and reattached the line. After several drive cycles, the light turn off.

    I suspect the heat from the engine dryed-out the vacuum line rubber, although the vehicle was only about 4-5 years old then (and not very high mileage).

    Some time later, I received the same code and replaced the EVAP vacuum solenoid (also mounted in the engine compartment). That eliminated the code again.

    Check all visible vacuum lines where they attach to a connector or vacuum source, especially in the engine compartment. If all are okay - I'd bet the gas cap seal is defective. If you replace it - don't go aftermarket but buy a replacement from your dealer. Good luck.
     
  7. chargermike

    chargermike Active Member

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    I went thru this on my 06 ram. Replaced gas cap. I checked and replaced hoses. Replaced purge valve. Each time I thought it was fixed only for the light to reappear. I did notice a strong small of gas at times near the fuel tank. My fuel pump module was cracked and after I replaced it.. No more light. May not be your issue but I thought I would mention it.
     
  8. mopar56

    mopar56 Active Member

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    OK, guys well all good ideas, I was working today and it was poring rain as well so this weekend I will go do some investigation, unfortunately for me it seems many different things can cause this problem so I will need to dig into it, my sons Neon had a similar problem and it turned out to be a split hose at the evap canister, so I will start with the obvious and check the gas cap, ( I like the plastic bag trick ), and I will take a good look at all the connectors, hoses, lines, and fuel module, I will let you know what I find, one more question in the mean time, I tried to erase the code with my scanner but it said " cant erase" anyone run into this?
     
  9. mopar56

    mopar56 Active Member

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    well I crawled around under the truck nothing really stands out, I here a slight whistle from the evap area on top of the tank but that may just be the fuel pump I here?, hard to tell from lying on my back, all lines and hoses seem soft and none have any cracks, same story under the hood, I removed the fuel cap which didnt take a lot of effort, maybe it wasn't tight?, I cleaned the o-ring and mating surface and tightened the cap and erased the code with my scanner, I drove about 25kms no light yet, hopefully it stays off
     
    ImperialCrown likes this.

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