What we can see here is the front brakes on an M3. The brake pads had been replaced by another garage but they had not replaced the brake pad wear sensors. The sensors are designed to short circuit when the brake pads are nearly worn out which causes the onboard servicing computer to alert the driver to this fact so he or she can arrange to have the pads replaced before they wear out completely and the car becomes unsafe. This is a system common to a lot of cars, not just BMW’s, but the BMW system takes things a little further in that the BMW wear sensor is actually a “Two stage” device. When the first stage activates the driver is alerted that the brakes will need doing soon. once the second stage is activated the driver is then informed that the brakes need doing as soon as possible. The garage that has replaced these brake pads has clearly not known that the BMW wear sensor is unique and has tried to fool the system by removing the sensors and adding a cheap plastic electrical connector to the wiring to cause a short circuit and in the process has damaged the insulation on the cars wiring loom. Needless to say the warning on the dashboard didn’t go away. Of course we were able to replace the sensors, repair the damaged wiring & reset the service computer properly but this was all extra expense for the customer who had already paid for the brake pads to be replaced and quite rightly expected the job to be done properly. We see this sort of thing all too often but we think that this particular job really does show that you get what you pay for.
The pictures on the left show the “Doctored” wiring loom and the missing sensor. The pictures on the right show how it should look.