Bought a 2007 SE with about 16,000 miles. When I back up slowly, I hear a few clicks and then a squeal, similar to really worn brakes. This happens only in reverse and WITHOUT my foot on the brake. Dealer says this is the brake sensor's early warning that indicates I need new pads. They claim with more wear, it would happen in drive as well. Is this true? Seems a bit early for brakes and is a stange way to warn of wear on the pads. Their "suggestion" is new pads, a sensor, and re-surface rotors. Don't really trust them.

Any thoughts?

Brake material is very easy to see . Also easy to tell if it is gone and in need of changing. 16,000 miles is very low mileage to need new brake pads but I don't know how you drive. I have 60,000 miles on my Xterra and 6 years of driving it in the city and I went through my first set. I bought new rotors and brake pads and it was cheaper than what the dealership would have charged me. If you don't trust one dealership try another . My local Nissan dealership is terrible so I drive 60 miles to another one and get much better service.

On many cars there is a "sensor" which is simply a piece of metal that will rub the outer rim of the rotor and vibrate to make noise when the brake pads get low. I am pretty sure this is what your mechanic is referring to. I agree that 16,000 miles is low and if it is only one set of pads that is worn out, you may have a caliper that is sticking. I would take of the wheel and check the thickness of the pads on the brakes. Inspect both sides to see if they seem to be wearing even. If not, I would say you have a caliper that is sticking and needs repair or to be replaced.