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Impala code P0455

Discussion in 'Non-Mopar Tech Support' started by Scrounge, Oct 9, 2017.

  1. Scrounge

    Scrounge Well-Known Member

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    2008 Impala, 3.5 V6. The CEL was on this morning, and the OBDII reader determined that it was from a P0455 code, meaning the Evap system has a leak. I bought gas over the weekend, so it's possible that I didn't tighten the cap properly. After doing so, the light remains on. Are there any common problem areas with this model that I should check? I don't smell any gas fumes. Also, would this be considered an emissions problem that the dealer has to correct for free? The car is now 9 years old (maybe 10, depending on when in the model year it was produced), but has only 56K miles.
     
  2. valiant67

    valiant67 Rich Corinthian Leather
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    The light won't necessarily go out as soon as the problem is fixed. If the problem is indeed fixed, it will go out after a certain number of drive cycles. Or, you can clear it (if the scan tool has that function) and see if it comes back.

    The federal emission warranty is 80k miles or 8 years so it's not covered.
     
  3. AllanC

    AllanC Well-Known Member

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    Here is a general schematic that shows the components GM uses for evaporative emission control on its vehicles. When the engine is running and at operating temperature, fuel level between 15% and 85% the ECM (engine control module) commands the purge solenoid OPEN and the canister vent solenoid CLOSED. Vacuum is applied to the evaporative system. Then the purge solenoid closes and the vacuum level is monitored as reported by the pressure sensor on the tank. If the vacuum is not maintained for a certain length of time, then code P0455 - large leak, is set. This test is performed multiple times before setting the code.
    Vapor System Schematic.gif
    If the situation is corrected it takes several drive cycles under the proper operating conditions of engine operating temperature and fuel level for the test to be run and clear the code. A trouble area is the canister vent solenoid. When it is commanded closed it can leak and cause the system to lose vacuum and fail the large evap leak: P0455 code.

    First thing to check is the mating service where the fuel cap meets the filler tube. If this vehicle is exposed to a lot of road salt, the metal surface that mates to the fuel cap can become corroded / rusted and form an imperfect sealing surface. Use sandpaper to clean and make sure it is smooth.

    Watch this Y T video on solving P0455 diagnostic code. Note that attention is called to inspection of the filler tube. Road salt can cause rust and pinhole leaks.


    View: https://www.youtube.com/watch?v=RwdgwRQZP7I
     
  4. Scrounge

    Scrounge Well-Known Member

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    Thanks for the feedback. I cleared it with the scan tool, and it didn't come on when I started the engine, but I've not driven it since then, so don't know if it will stay off.

    I usually don't drive the Impala more than twice per month, so vacuum not being maintained might be an issue. But the CEL stayed off when I drove it on Saturday. Though the car came from Michigan, it was garaged, and I don't see much oxidation.

    Interesting video. They don't make these easy to repair!
     
  5. Scrounge

    Scrounge Well-Known Member

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    After a short drive, the light stayed off. Hopefully, I just didn't put the gas cap on right.
     

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