PO455 Code

Discussion in 'LS, LT, LTZ' started by Kody, Mar 25, 2019.

  1. Kody

    Kody Junior Member

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    So my engine light is on and when I connected my scanner it gave me this code;

    PO455 - Evaporative Emissions System Leak Detected (large leak).

    There are no other indications of a problem and when I clear it the code comes back in a day or two. Anyone else have this problem and know what could be causing it?

    Any help would be appreciated.
     
  2. Shaggy

    Shaggy Administrator Staff Member

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    Get it worked our or still having issues?
     
  3. greggn

    greggn Junior Member

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    Loose or defective gas cap.
     
  4. Dennis Schiller

    Dennis Schiller Junior Member

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    OP may have moved on...
    My 2006 has had the code for 5 years now.
    Been to more than one garage and I try to figure it out every spring.

    I'm convinced now it is the ECM.

    Gas cap is first thing to check.
    Then my preferred order of testing is this.
    Remove the two solenoid valves and bench test.
    Remove the pressure sensor and bench test.
    Re install if working properly.
    Key on, engine NOT running
    Energize the vent valve with external 9-12VDC source to close the system off .
    Use OBD scanner to see if system pressure creeps up (due to gas vapor pressure).

    If it does not creep up, there is a leak, use soapy water in spray bottle to locate
    (Should lower gas tank to check top connections)
    A smoke test may help.

    If it creeps up and holds steady, there is no leak and a smoke test will not help.

    In NJ this single code will not prevent passing State Inspection as long as it is cleared before attempting to drive through inspection station.
     
    Last edited: Apr 24, 2019

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