This is something quite fancy on a '21 as the PGM needs to know what gear the bikes in.
On an '18 and '28 it's just a wire, I snipped mine off on the race bike
If that's the case it's of use if you're doing a tidy job on a race bike and don't need a GPS.
Unplug the neutral wire on a stock carded '28 and it won't run in gear (will it Tom?).
It looks the same for a normal loom and PGMIII'd '21 (as the neutral wire goes back to the PGM), on an '18 it just means the neutral light stays on.
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