Welcome to the forum
Sounds like the pex line is vibrating. There should be a panel that you can remove to access the pump, it may have screws holding it or you may have to remove a panel in the front storage compartment.
Once you’ve gained access you can determine a course of action. Maybe a couple of zip ties, or maybe some pipe wrap. There is access to the pump, just gotta find it.
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2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.