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  1. #1
    Sr. Apprentice WI_z71's Avatar
    Join Date
    Nov 2007
    Oak Creek, WI

    Default Check engine code

    Hello all,

    The other morning I turned on the truck and the check engine light stayed on after all of the lights usually turn off. I immediately got out and checked the normal things, oil, tranny...things like that, tightened the gas cap, it still stayed on. So I drove to Autozone and had them read the OBDII code and it came up 42 (i think) which was a small evap leak. I felt the gas cap and it was secured but felt kind of loose, so I bought a gas cap and exchanged it out. Well it has been about 2 days now, and the light still has not gone off...What else could be causing the evap leak??

    It is an 05' Silverado z71 with about 50,000 miles.

    Thanks in advance!

    2005 Chevy Silverado z71.
    - Readylift Leveling kit
    - Cooper Discoverer STT 285/70/17s
    - Line-X over the rail bedliner

  2. #2


    Did they clear the code after reading it? If the cap was the problem, the light will stay on for a while before going out. Have them clear it, and if it comes back on, then you know it wasn't the cap...

    Start there, after that, they should have the OBDII manual, which tells you several different options. If not, I googled mine, and found all kinds of help...

    Hope that helps.

    2007 Silverado LT Z71 4x4 Crew Cab
    Dark Metallic Blue

    Mods to come, just purchased on 10/31/09

    Go Pack Go!

  3. #3


    It's hard to keep all these trouble code procedures straight. If not already cleared, is this one that will self-clear after 50 starts, or will a brief power interruption clear the code?
    Are we having fun, yet?

  4. #4

    Join Date
    Feb 2008
    Red Wing, Minnesota, United States


    the 42 is listed as specific to the carbon canister and small leak, in the engine compartment but it will throw for the gas cap too, the gas cap is actually 41, get a new gas cap , then clear the codes and have no problems, i have been in the clear now for two weeks
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual

  5. #5


    FYI: The California Air Resources Board (the infamous CARB) says carbon canister problems are prolific, so they have added a comprehensive Low Pressure Fuel Evaporative Test to the Smog Test inspection for 1976-95 pre-OBDII vehicles.
    Perhaps, some day there be CARB approved jars to fart in.

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