Diagnostics Doctor
Your electrical queries answered.
My 2005 BMW E53 X5 3.0 diesel sport auto with the M57N engine has a full BMW service history and nearly 42,000 miles on the clock. The other day when parking, I got a continuous beep when reverse was selected. Before this happened, I had been driving on a very uneven road surface, which could have dislodged something. It has been suggested that this is a sign of a faulty sensor and to listen to each one to check if they are clicking – the idea being that the one not clicking is at fault. The problem is they are all clicking. Do you have any other way to find the fault? Paul Finnegan A continuous tone indicates a fault within the parking sensor system and is often due to a failed sensor. However, the faulty sensor is not necessarily at the rear, even though the problem occurs when in reverse.
If you’ve not already done so, check the front sensors while reverse is selected, using the same method you have used for the rear – with the ignition on, the engine not running and reverse gear selected. Listen for a clicking from each sensor. If this check shows all front sensors to be clicking, then further investigation will be needed. Using a Bmw-compatible scan tool would enable full diagnosis of the system and would be the easiest method, but it’s possible to make a few checks using a multimeter.
The sensors will have three wires: one is live, one is earth and the third goes to the control unit. Using a multimeter, you can check for a 12V feed to the sensor and for the continuity of the earth. You should also inspect the connections to the PDC module, which is located behind the battery.