Engine Harness - Part 4 - Continue with Wiring Investigation

TLDR

• Continued to investigate the ECU issue

Details

Fuses and Power Wires

So continuing the investigation on my ECU issue, I have been in touch with MWPB, and they suggested to check a bunch of things on my harness.

In no particular orders, I checked the following over a few days of work:

• Disconnect the starter relay, and turn the ignition key
  • No change in engine instruments, still all red-x.
• Opened the Rotax fusebox, and checked the fuses
  • 3 fuses were blown!! 35A, and two 7.5A fuses.
• Check the wiring on the connector that supplies power to the Rotax fusebox (ie. RE1 connect)
  • continuity test between pin 1&56, 1&7, 2&6, 2&7. Since 1 is supposed to be power and 5 is ground, I expected 1 & 6 have contunuity and 2&7 have continuity. However my test result was 1&7/2&6 have continuity.
  • Under advice from MWPB, I also tested the load between 1&5 using a incandesent light. It lit up. So there is load between 1 & 5.
  • Also tested voltage between 1 & 5. It shows -12V.

So a lot of signs pointed to that my RE1 1 & 5 were swapped. I swapped them back with the help from MWPB over phone and email. Initally I tried to depin using a special tool MWPB sent me. But I was only able to remove one out of the two pins out of the connector. Eventually I gave up on that and just cut the 2 wires, and reconnected them in the right order using a crimp splice.

Once I did that, I did another test by turning master and EMS BKUP on. On G3X the engine instrument was still blank, but the good news was that the LED lighgts on the fusebox all lit up, and the lane lights looked much more normal. It turned on for 5 seconds then went off. From what I read online this is the expeced behavior for Rtoax ECU start-up.

Blown fuses

Swapping the pins on RE1

Crimped the wires in the correct order

LEDs in the fusebox

However still blank on G3X

No CAN bus for FADEC

BUDS Reader Test

I connected the two maintainence ports on the ECU to my BUDS reader, then turned on the lane switches.

The BUDS software recognised my engine and showed no error. All instruments were ok on my computer.

So I think this means the ECU is working fine. And the problem is CAN wiring.

Tracing CAN wires

I designed a few tests to trace the wires between ECU and G3X, specifically between the 2 HIC connectors and the GEA24 J244 connector.

According to my diagram, the following should be true:

1. GEA J244 Pin 17 white wire(CAN HI), pin 33 white/blue wire (CAN LO).
2. HIC-A #6, HIC-B #8 and GEA J244 #17 should have continuity since they are spliced together according to my wiring diagram (I don’t have SCU)
3. HIC-A #5, HIC-B #7 and GEA J244 #33 should have continuity for the same reason.

I used a multimeter to test these connections. The results were:

1. Appears to be correct
2. No continuity
3. No continuity

So the problem is somewhere between the HIC connectors and the GEA24 connector. I removed the G3X screen from the panel to expose the harness wires, and used a boroscope to look for where the HIC wires and the GEA24 wires spliced together. I found a connector that’s supposed to be a jumper to merge the 6 wires together. I suspect the issue is with the jumper.

G3X removed

The jumper, though it does not look like looping any wires around internally. Next step: take it apart and look inside