Parking Sensors Fixed!

[chrisalis1]

Quick resume´.  Went through every post and I was feeling the same frustration as most posters were having with the problem of their parking sensors not working! "Listen for clicking", "bad connection", "control box u/s"...I went through all suggestions.   I was getting intermittent failure of my reverse sensors on my 2005 E46 touring. Place car in reverse and long beep for several seconds. All the sensors clicked when I put my ear against them. (If you put a screwdriver tip on them and the handle against your ear it can help if surrounding area is a little noisy. Acts like a stethoscope) I noticed that when my sensors were in the sun they failed. Ok so I bought four new aftermarket sensors off of the net. Put the new ones in and zilch....nothin! Not even a long beep now!  Time for a rest to clear my head. I then had a bit of a eureka moment as for some reason I remembered reading somewhere that a lot of aftermarket dealers were required to stipulate that these aftermarket jobbies only worked in the centre positions and not on the two far corners or end positions of the bumper or bumper insert in my case. They were forced to stipulate this after many disgruntled purchasers were returning the sensors as faulty even though they were all giving out good healthy clicks. Ok, so my old genuine BMW sensors were out of the car now so if I tested them somehow could I possibly have two good ones to put back in the two corner positions? I used a multimetre 200 ohm setting and placed one probe on the centre pin holding the sensor with centre pin closest to me and the other probe to the top right pin. I had a reading of 42 ohms for three of them and only 32 for the other which I gathered was the faulty one. I replaced the two new sensors at left and right ends that I had just put in, with the old BMW sensors with the 42 ohm readings leaving the two new aftermarket sensors in the middle and hey presto the parking sensors came back to life once again. Aftermarket sensors in a lot of cases will simply not work unless they are positioned in the centre. BMW ones will all work on the two outside positions. If you ever discover a faulty outside sensor and they are the real McCoy, then move one of the central position sensors to the outside and replace the centre with an aftermarket if you need to save a bit of dosh. The BMW parking control system will simply not recognise an outside sensor unless it is a genuine one. Well I've got two spare centre position sensors now for spares!

[Davcbar]

Just had a very similar experience. Only with old BMW PDC sensors in position 1 and 4 will my PCD work on my 2002 320i touring. The PDC has been out of order for six months since I changed all four sensors for new from Autodoc. Had to resort to buying an Autophix 5900 scanner to find out what was going on. This gave no fault codes but revealed only the center sensors were providing a distance signal. Sensors 1 and 4 were stuck on 255 centimeters. Only when I put in two old BMW sensors in position 1 and 4 did the system fully work again. How long this fix will last I'll wait and see.