The Ebay PDC sensors are garbage. The VEMO? ones that are about 1/2 the price of the OEM work reasonably well but not as good as the originals. If you use IMPA or DIS you can get a live reading from the different sensors and see how they measure up for yourself.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)