N997CZ — CAN Bus Rewire: Fixing the Basics Before Chasing Vibration

After the ADAHRS vibration analysis across the first five flights, Garmin’s guidance was unambiguous: fix the CAN bus first, then work the vibration problem. The data showed sustained % deviation throughout every flight — but some of those readings may have been contaminated by CAN bus dropouts rather than pure vibration. You can’t separate the two until the bus is clean.

So before touching the prop balance or the ADAHRS mounts, we pulled the old harness and rewired the entire CAN bus from scratch with the correct 120Ω controlled-impedance spec wire.

Before and After: Every Node on the Bus

The CAN bus in N997CZ runs as a daisy chain from the PFD1 terminator through thirteen avionics boxes to the roll servo terminator at the far end. The measurements below are the wire lengths between adjacent nodes — not the lengths attributable to any single box.

What’s Next

With the CAN bus now on spec wire and properly sized, the next flights will establish a clean baseline. If the % deviation drops significantly, that confirms the old wiring was a major contributor. Whatever remains after that points squarely at vibration — and the prop balance, SB 2144 GSU assessment, and mount evaluation are queued up to address it.