Code P0456 02 Dodge Dakota

i had code 0456- small evap leak detected- on 02 4.7 dakota. i replaced the fuel cap with after market stant and check engine light came on after about a week. i had a scan done and it showed no problems detected. so they cleared the code for me. about 4 days later. the check engine light came on again- still no trouble codes detected. has anyone else run into this problem? im still driving with the check engine light on, because i don't know what else to do. any help would be gratfully welcomed.

That makes no sense. The light is on for a reason. Are you saying that when the scan is done, it turns up no codes now? Who is doing the scan for you?

check the posts that i put up earlier in the forum in response to the problems with TWL's truck. Do a good visual inspection of all the vaccum lines in the evap circuit, especially around the back of the cylinder head etc and towards the fuel tank

Might aslo be a software update available that addresses erroneous po456 codes on some years of dakota's

Every OBDII vehicle has two sides to the computer. The OBDII side and the manufacturer specific side. It is very likley and possible for a code to set in the manufacturer specific side and not in the OBDII side of the computer. If using a scan tool that only pulls data from the golbal OBDII side of the PCM, then you may be missing manufacturer specific codes.

Thanks to all who have offered advice on my p0456 problem. I am going to start by getting a mopar gas cap from my dealer, but every dealership around my area has these on back order, so I will have to wait a week. While im at the dealership I am going to try to have an understanding that if the new cap is not the problem, then I do have two tsb's I can quote -18-016-02a--18-002-03 that proves this is a pre-existing problem ..apparantly this is a "phantom"code problem if the cap is not at fault. I dont feel I should have to pay for this , so I might have a fight on my hands. since Tennessee is an emission testing state, I have until July to solve this before going to the testing center. Once again thanks for the great posts. I am learning a lot.

Not really a phantom problem, just a very common problem as seen by the fact that the gas cap is back ordered, like I said in other posts check all the vaccum lines you can access, very common for the ones under the truck to crack, get ripped off etc, especially off roading.

Keep me updated please

Jeff

I went to dealer and got a new Mopar gas cap and they cleared the check engine light for me. The light came back on again 2 days later. I showed the service writer and tech the 2 tsb's on trouble code 0456. They said I needed a smoke test to track this leak down. I have looked and inspected all the hoses I could find,but I did not see any cracks or cuts on anything. There are some hoses that go behind or beneath some things I can't move. If the cannister is clogged, how do you test it? I know these smoke machines are expensive. How much should I expect to pay to have this smoke test done? THANKS!!

I personally have never seen a clogged cannister on a dakota while working at the dealer, now that being said anything is possible I guess?
If you know how to use the smoke machine then it can tell you if the cannister is clogged by looking at flow through the components of the system, I still say you probably have a cracked hose that yuou can't see but you could also have a valve, pump issue etc. There's also TSB's fro some dakota's that address erroneous dtcs for evap leaks meaning the code is being set under certain conditions but the system is still sealled and functioning as it should. It essentially reprograms the PCM to be less sensitive, they'd have to run the software # in your PCM to see if the flash is appplicable, Lastly with the dealer scan tool these codes are relatively easy to fix because the factory scanner will actuate all components in the evap system plus run a test after any repairs have been done to check the sealing capacity of the system, so if your truck is failling the monitor that frequently then it should be easy to find the leak. If your dealer doesn't have a working smoke machine then find another dealer because they probably don't know what they're doing anyway.
At the dealer I work at we normally charge 2 hrs diag time to find any leaks or failled components in the system and additional time to repair the system depending on what it is. Small hoses leaks etc we normally don't charge to repair unless there's things to remove for access because we often have to repair the hose prior to running the systems test with the scanner. Very rarely do I have to use the smoke machine to find the leaks in these systems because you begin to learn the common places to look. That being said I do find that using the factory scan tool to run the systems test saves me alot of time because I can verify right after the reapir whether or not it's gonna leak agin. Finally overfilling your gas tank will cause this code to keep reoccuring because the cannister will become flooded. When the nozzle clicks off it's full!

Anyway sorry about the wordy response, call your dealer for a quote for some diag time if you fell your at that point and keep me postted, like i said I work on these alot so if there's anything I can do to help feel free

Cheers and Good luck

Jeff