E39 Airbag Sensor

Based on the dealerships and their attitudes towards helping their customers, I was determined to solve the problem with the Airbag light remaining on and did some more research on the internet. I found a solution, or part of one at least, again another common fault it seems for the BMW. Due to wear and tear of seats being pushed backwards and forwards eventually causing the sensor to malfunction. During my search on eBay I came across a 'Sensor Bypass' that clicks into the existing sensor housing under the passenger seat.(e.g. below). It also allows the airbags to go off if involved in an accident.

There are different styled sensor bypass units available and I did purchase one prior to the rounded one. This one, with a square box on the end, has two wires connecting the box to the rest of the unit. The box and wires could move and the wires became unsoldered inside the box causing malfunction, personally this type is not recommended as the problem or wire detachment is not always evident and there is no access to repair the solder joint, without damaging the casing.

Note: The all-in-one rounded sealed sensor is the one that worked for me. This type recommended.
Bought the bypass off eBay for £12.55 ( b.l-shop-47) this also allows the bags to go off if there is an accident.

Sometimes one can get away with just replacing the 'Passenger Bypass Air Bag Sensor' by pluging it into the box under the rear passenger seat and the light goes out straight away on the dash and at other times the light doesn't go out. On the latter, an OBD II Scanner is required to tell the onboard computer that the fault has been fixed and now the error can be switched off. This means either taking the Beamer to the Dealership and paying a fortune or by purchasing a cheap OBD II Meter...(see page 11) and do it yourself, much cheaper.

Note: On turn of the ignition switch positions one and two, the airbag light illuminates and goes off after about three seconds, this is normal. On insertion of the bypass, this function should be reinstalled. If this is not immediate, you will require the OBDII to switch off the fault. Be aware, you may need to go for a drive around the block for your ECU to acknowledge the change. In my case, this was not necessary. It does save paying out £480 to the dealership. Mine is working fine now.