I'm flying a Sling2 with a 912iS Sport Engine. First flight Nov 2019, currently at 254 hours on engine.

For the last 2 months I've been trying to figure out a Lane A flashing light when I bring my throttle to idle in the landing pattern. My Garmin 3X FADEC information shows it as a Lane A Status: Advisory, and Cylinder 1 EGT Sensor Fault and Cylinder 4 EGT Sensor Fault. I can watch the engine monitor page on landing (and also memory logs) and all 4 EGT show around 1300-1400 until I pull back to idle and then I can see EGT1 and EGT4 decrease to the 500-700 range. After the Lane A light starts to flash the EGT1 & EGT4 temps start to rise (throttle still at idle), and in 15-20 seconds they are back up to where they should be. An interesting observation is that if I leave Lane A flashing and bring the rpm up back to cruise for a while and then once again bring the throttle back to idle all 4 EGT stay where they should (1300-1400).

My engine seems to be operating great, so my 1st assumption was that I had a couple of bad EGT probes. So I switched probe 1 with probe 2 and also installed a new probe on cylinder 4. No change in the problem, EGT1 & EGT4 failure.

I've reseated the Lane A connector to the fuse box, including using dielectric grease on the connector, and again no change in the problem.

I now started to think that maybe there is something going on with the engine where what I'm seeing on the engine monitor is correct and something is causing the exhaust temps to fall (even as I don't detect any engine problem). So I installed new spark plugs and on cylinder 1 & cylinder 4 I trimmed off 1/4" of the spark plug wires and reattached the original caps. Again, no change in the problem.

I don't see how it could be a coil as I understand that cylinders 1 & 2 share coils and cylinders 3 & 4 share coils. My problem is with cylinders 1 & 4.

- I can't reproduce on the ground.

- FYI, my idle is set to 25% so around 1900 rpm on the ground and 2600 rpm in the pattern

- What is shared between cylinder 1 and cylinder 4? There must be something common as these 2 cylinders started to fail around the same time 2 months ago.

- How does the engine operate differently when Lane A is flashing?

Thanks for any and all advise.


  • Re: EGT Sensor Fault

    by » one year ago

    Bill Asked: (The other Bill !)
    How does the engine operate differently when Lane A is flashing?

    You have the question backward.
    You should be asking, "When the Lane A lamp flashes, What in the engine is operating differently.

    The Garmin is recording the Effect of the Fault (Cold EGTs) not the Cause of the Fault (???).

    When the Lane A lamp illuminated, Lane B took control of the failed system, restoring the engine to normal operation.
    When the Lane Light Flashed, it saw a fault and logged the fault to the ECU Error files.
    Connect the BUDS Software to the engine and interrogate the ECU Fault File.
    Then you will know what the true cause is instead of blindly replacing good parts and guessing at the problem.

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

    Thank you said by: RotaxOwner Admin, Bill Hall, Joe

  • Re: EGT Sensor Fault

    by » one year ago

    I have a similar problem with my RV-12iS.  It has a Rotax 912iS engine with about 75 hours.  I can create an EGT 3 Sensor Fault by flying at night and reducing throttle to Idle.  I then begin a descent, simulating engine out failure. 

    Watching the EGT gauges, I can see EGT 3 cool down slower than the others, and it remains quite a bit hotter, by maybe 200-300 deg.  Lane A comes on Flashing; look at Engine Faults, see: LANE A SENSOR EGT 3.

    I believe the problem is a result of the LOCATION of EGT 3 sensor on my engine.  It is buried toward the rear of the engine and is close to the oil canister and surrounded by hoses.

    The result is EGT 3 is reading correctly, but a higher temperature because the exhaust is higher.  Cycling Lane A status turns off the flashing LED, engine runs fine.

    This does not happen under identical circumstances during the day when OAT is higher.

  • Re: EGT Sensor Fault

    by » one year ago

    The EGT Sensor is measuring the Temp of the Exhaust Gases 5cm from the Exhaust valve in the middle of the gas flow.
    It is NOT measuring the temperature of the metal of the Exhaust pipe.
    If the Fault says  " LANE A SENSOR EGT 3",  I would tend to believe it is a Sensor Fault.
    Swap the Sensor with that of another cylinder and see if the fault moves.

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

  • Re: EGT Sensor Fault

    by » 12 months ago

    Problem fixed :)

    Finally received a dongle so I could read the BUDS error logs (the dongle was on back-order for 4+ months). It showed multiple injector errors on lane A cylinders 1 & 4. So I replaced fuel injectors 1 & 4 and the problem has gone away. I notice that the engine now also starts better and runs smoother when I do a lane check with lane B turned off. FYI it wasn't that hard to replace the injectors... took about 1-1/2 hours start to finish.

    I'm surprised that I had to replace 2 injectors after only 280 hours on the engine. I run only premium mogas. I also see that other people seem to have the same problem needing injector replacements. Has anyone successfully used fuel injector cleaners in their fuel system?

    Thank you said by: RotaxOwner Admin

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