When you're driving if a constant clicking/rattling annoying noise starts, try pushing DOWN on the passenger seat next to you. If the noise stops, then it's one (or more) of the seat's bottom rail floor mounting bolts. Sometimes they work loose in their mounting holes and rattle against the metal. I tightened up the loose one I found on my 2010 base Fit and presto, no more clicking or rattling noise!

(A clue: If you or someone else is sitting on the passenger seat while traveling this noise will usually disappear then also, as the rail bolts are then getting downward pressure!)

 

There;s a TSB for the 2010s on this. The bolts need to be tightened to a higher torque setting.