1st check by turning on the PDC on and have someone walk close to the ones up front. You could do this by yourself because those sensors are loud...lol

You also should go to the service desk at the dealer and get a print out of all your maints records then you can see what was done or not. In Dec i went to the dealer were the PO bought and took it in for everything and i bought it from that same dealer. I found out a lot of info that i was wondering about.
example: TC went out (no fluid in it) around 30k so they added a new one, h20 pump was replaced 3 month before i bought it and went out while the dealer was trying to sell it, brakes were just down and still have 6mm on them, PS hose was replaced, new tires were bought at 50k, 2 batteries were bought (1 at 30k and another at 50k) and on and on.... Also the PO got hit (little hit but 4 month after buying it, sad) and needed a new rear bump and PDC sensors...and had to bring it back 2 or 3 times after because it would go off when their was nothing close by...

If the PO got the sensors fixed then they should have a 2 year warr. on them. The service guy at my dealership told me that all parts have a 2 year warr. on them...

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2001 X5 3.0i "Dodi"
1993 Range Rover County LWB (71,600 miles) "Bertha"
1991 Range Rover parting out