Can Bus, which is negative wire?

[tinpusher]

I'm installing a Garmin Montana and purchased the 3 wire connector which attaches to the spare Can Bus outlet next to battery. It wasn't tough to find out which is positive but the remaining 2 wires both complete the circuit. Can I use either one as negative/ground? There are no markings on the connector or wires.
2010 F800GS

[PegasusJockey]

1) positive
2) rpm pickup
3) negative
If memory serves

[Slappyhamguy]

I'm installing a Garmin Montana and purchased the 3 wire connector which attaches to the spare Can Bus outlet next to battery. It wasn't tough to find out which is positive but the remaining 2 wires both complete the circuit. Can I use either one as negative/ground? There are no markings on the connector or wires.
2010 F800GS

Where did you pick up the 3 wire connector?