Lane A Red, Lane B Flashing Red

While I did loan my BUDS Dongle to Ray, I'm afraid I have not been much help to him in solving this problem.  Does anyone know what kind of wiring or sensor problem would only show up when both lanes are active? The AATP sensor is on Lane A, and the Oil Pressure Sensor is on Lane B. Either lane works fine with only one lane turned on. Once both lanes are turned on, both the AATP sensor and Oil Pressure Sensor show faults. That would indicate to me that each of these sensors is working fine, and something else is at play. 

We have verified the reference voltage (5 VDC) is correct at each sensor. We get an actual reading of 4.95 VDC, but close enough. And we have verified that this voltage does not change when one or both lanes are turned on. We have also tested continuity through the harness to each of the two sensors in question. It also appears that the readings are correct on both the Oil Pressure and Outside Air Temp and Pressure gauges, even when in fault. 

A wiring problem seems unlikely, since the plane operated for almost 40 hours without this problem. It's also a strange coincidence that these two sensors look to be on the same I/O positions on the two ECU lanes. In other words, they are both in the 15th sensor position down the list when looking at the BUDS Screen. I'm beginning to think this may be an ECU problem.   

Update:

After 4+ months messing around with the Rotax service center (CA/Utah) they have finally asked for the ECU and FUSE Box to be sent to them for testing. ($400.00 US with insurance! OUCH!!)

Perhaps I will get somewhere with this problem.

It looks like the ECU is toast. 

Latest update: This saga is not over yet.

In my previous post I had sent the ECU to the Nearest Rotax service center where it was plugged in and tested. The info I received back was it was showing to be defective in his opinion.  The Rotax guy didn't have a serviceable ECU to send out so he got the Midwest Service Center involved. A week later I received the loaner ECU and installed it into the aircraft where it promptly failed exactly as my original ECU had. I had also received a loaner Oil Pressure sensor from Wisconsin because they said they had seen similar failures caused by the OPs. I plugged it in and there was no improvement. 

At this point I had checked every possible item I could think of checking. Both sensors had been changed out, the ECU had been changed out, the fuse box had been sent to Rotax service and checked. The wiring harness had been rung out for shorts, opens, and all grounds had been checked and verified. Grasping at straws and at the recommendations of the nearest Service Center I purchased an Engine Wiring Harness and installed it. Another $2 GRAND DOWN AND NO FIX. 

At this point I had over $5,000. invested in this problem, Changed out every conceivable component that could possibly cause this problem and no solution. I gave up and decided to pull the wings and haul the beast to the Rotax repair center In Petaluma 100 + miles away. When they were able to get on this they started from scratch, Pulled the error codes that showed OPs and AATPs failures (specifically the PRESSURE side), the same as I had found.

The easiest, first thing, to change is the AATPs (Ambient Air Temperature and Pressure sensor), I had to purchase one for $330+ when I changed it back in December!  They didn't have a new one in stock to change out, but they did have several aircraft they could borrow one from. When they changed the AATPs the failures went away! They then put my AATPs into their airplane and it immediately showed OPS and AATPS faults!

Who would ever guess the first part I bought to fix this problem, 7 months ago, would have the exact same failure that caused the original problem. What are the chances a modern electronic part sealed in the original factory packaging would be defective in the same manner. This sensor has two different circuits, one for temperature and one for pressure, The defective circuit in both is the pressure sensor, the temp. circuit of both still works! What are the odds?

Hopefully, when I can get the airplane home and reassembled with the Second new AATPs, just received, this Saga will be put to bed for good!

I was in contact with Ray over the last few months as he worked through this problem. The most notable thing about this was that the fault would only show up with both lanes on. The AATP sensor is on Lane A, and the oil pressure sender is on Lane B. With BUDS connected, when either lane was on by itself there were no faults.  However, when both lanes were turned on both lanes went into fault, with errors showing in both the OPS and AATP sensors. Of course the first action would be to replace those sensors, which was done.  However, once done, those items were checked off of the troubleshooting list (at $330 each it’s hard to motivate yourself to try replacing them again). Thanks for sharing your experience Ray.