Error code p0456?????

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Cadillac XTS Forum Discussion, Error code p0456????? in Current Cadillac Vehicle Discussion; My 2014 XTS was giving me the P0171 error code. I was told that I was in need of an ...
  1. #1
    twanlo456 is offline Cadillac Owners Member
    Automobile(s): '14 XTS Luxury AWD
    Join Date
    May 2018
    Washington, D.C.

    Error code p0456?????

    My 2014 XTS was giving me the P0171 error code. I was told that I was in need of an Mass Flow Sensor. I changed the sensor with a OEM AC Delco sensor. Check engine light remains, now I’m getting code P0456 (EVAP) issues I guess. Can anyone provide in hits or tips to fix this situation? Thanks in advance for any and all replies!

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
    Join Date
    Feb 2006
    MD Eastern Shore, Kent Island

    Re: Error code p0456?????

    Take out a multi-year subscription to - it's the online version of the GM/Cadillac service manuals for your car. When you open the home page there's a menu on the left side. At the top is "Diagnostic Trouble Codes". Scroll down to your problem code, click it, and it opens a system description, problems, and diagnostic trees.

    P 0171 is a lean mixture, left bank. Usually a vacuum leak, not the MAF. Diagnose the problem instead of throwing parts at it.

    P 0456 is a small EVAP leak - gas cap, fill pipe, tank hosing, charcoal canister, EVAP purge solenoid, EVAP test port (capped with a green valve cap) - near the throttlebody, black plastic pipe.

    EVAP stores fuel tank vapor from expansion and burns it during highway steady speed running.

  4. #3
    Ken4 is offline Cadillac Owners Member
    Automobile(s): 2016 XTS platinum
    Join Date
    Mar 2019
    Eastern Tennessee, USA.

    Re: Error code p0456?????

    I had a small EVAP leak that came and went on another GM car that I had. Turned out to be the tank seal for the fuel tank and sending unit. They used a machine that makes some kind of smoke to find the leak. They told me that this seal is the problem a lot when it is not the obvious.

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