A friend and I are ferrying a 912iS powered Kitfox halfway across the country.  We flew the first two legs today: 3 hours, a half-hour break, then 2 hours.

On both legs, the Lane B light illuminated during cruise, after about an hour of flight.  On the second leg, the Lane B light was shortly followed by an “ENGINE ECU” alert on the Garmin G3X.

During the first leg, both fuel pumps were operated continuously and during the second, only the #1 pump was running.  Both legs were flown at wide open throttle.

In neither case was there any obvious change in engine performance.  No roughness, no loss of power, nothing.  The G3X monitors both voltage regulators; both were steady at 13.8V.  Oil temperature and oil pressure are continuously in the green.  Coolant temperature is probably a little low, at 160°F, but we were operating with OAT as low as -14°F and the cabin heater running the entire time.

This is a recent production engine (less than 2 years old) with probably under 100 hours total time.  The engine is equipped with an Airmaster constant speed prop.  Climb setting is ~5,450rpm and cruise setting is ~5,250rpm.

Neither of us has very much Rotax experience and we don’t have a BUDS dongle.  Any help diagnosing these symptoms would be appreciated.  If diagnosis isn’t possible, we would appreciate reassurance that an engine failure is not imminent.


  • Re: Lane B Light + “Engine ECU”

    by » 4 months ago

    A flashing lane light generally means a minor fault, whereas a steady light means a major fault in that lane.  If a lane light is on steady, you should consider that lane non-functional, which effectively leaves you with one working set of injectors and spark plugs. That’s kind of like flying with one bad mag on a standard engine. If the light is on steady, the Rotax recommendation would be to land as soon as possible.

    Without the BUDS dongle and computer this will be hard to diagnose unless you just get lucky and find a bad connection somewhere.  You can get more detail on the error code from the G3X directly, but you have to do it while the ECU is in fault because the G3X will only display active faults.  And, unfortunately, to see the fault code you have to reboot the G3X PFD into Config mode, which will put the second display (if so equipped) into config mode also.  This is too risky to do in flight, so you would effectively have to get the fault to happen on the ground and do the check before cycling the lanes (which may reset the fault).  The link below will direct you to a video showing how to enter Config mode on the G3X and check the fault code. 

    That said, it would be much easier to have it checked with the BUDS software, which will read all faults stored on the Rotax ECU.  


    Thank you said by: Eric Page

  • Re: Lane B Light + “Engine ECU”

    by » 4 months ago

    As you saw, the engine will run 100% fine even with multiple errors.
    That is the beauty of the redundancy built into the 912is and 915is engines

    Possession, or at least Access to a BUDS Dongle is not an option for a 912is owner.
    Because the engine faults with no symptoms other than a Lane Lamp, you can't tell what the problem was without one.
    A Level-3 dongle is highly recommended.

    WOT is not recommended. I know you were under the 5500 rpm limit but a little backing off wouldn't hurt.

    Your 5450 setting with the throttle pulled to lower the Map below 25" would be better than the 5200 setting.
    Of course, if you were above 5000' and 25" was not reachable then WOT would be fine.

    If the Lane Lamp is only Flashing and Not Solid, and it can be reset by power cycling the ECU Lane; Fly On!
    But get it checked out when you get to your destination.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

    Thank you said by: Drew Broussard, Eric Page

  • Re: Lane B Light + “Engine ECU”

    by » 4 months ago

    Thanks very much, guys.  I appreciate the quick overnight replies!

    I should have mentioned that our departure airport was above 5,000 feet and our cruise altitudes were not below 7,500 feet due to terrain (we started in the western Rockies), so WOT didn’t exceed 25” MAP.

  • Re: Lane B Light + “Engine ECU”

    by » 4 months ago

    Quick follow-up on this issue.  The symptoms continued unchanged on a subsequent flight and on the ground the engine died when the Lane A switch was turned off.  The aircraft has been hangared awaiting attention from someone with a BUDS dongle and the ferry crew has returned home.  If I learn more, I'll update this thread.

    Thank you said by: Bill Hertzel

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