2008 Outback check engine keeps repeating for fuel cap?

I bought a 2008 Outback w/150k miles on it last fall and maybe about April when I was supposed to go in for emissions testing the Check Engine light came on and Cruise control light started blinking. The dealer said it was the fuel cap, so I ordered a new one, but that trouble code keeps repeating every time the tank drops to about half full. I finally got to stay off long enough to do the emissions test before the end of May.

But it has since come on again. I ordered an OBDLink LX, so I could check it myself and same thing, fuel cap. I made sure the cap was tight, cleared the code and the diagnostics does not show any pending code for that yet.

What could cause that fuel cap trouble code to keep triggering if I always make sure that the cap is on tight and seems to happen when the tank is down to half full? Could it be a bad sensor and where would that be located?

Update:

If it happens again I will have to get the actual code. Both the dealer multiple times before and OBDLink software for the Bluetooth OBD II reader mentioned fuel cap. Although, I don't know how it could detect that vs. evaporative system leak. I did have a minor accident in November 2015 that shifted my front bumper about an inch to the right hitting a left turner on a rainy night, but the codes did not start happening until April 2016.

3 Answers

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  • Joe
    Lv 7
    4 years ago

    What numerical code are you getting?

    There are a whole series of evaporative emissions self-tests that the car runs. The leak tests either report codes for a "small leak" or a "large leak", either of which could be the fuel cap (or a leak elsewhere).

    BUT: With some Subarus, there's another test that is only run when the tank is half-full, or less. I'll bet that's the test that your car is failing. On my 2001 Forester, it produces a code P1443. This has nothing to do with the gas cap.

  • Mr.357
    Lv 7
    4 years ago

    I have NEVER seen a code for a bad fuel cap. Mostly they are for leaking pressure in the fuel system. Most probably you are getting a P0440 code that means there is a vapor leak in the fuel system, not just a bad gas cap or a loose gas cap. Any of the hose or steel line connections could be leaking.

  • Nomadd
    Lv 7
    4 years ago

    A leak anywhere in the tank or vapor recovery system can cause it.

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