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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22154
Experience:  BEng hons Mech engineering, in auto industry 22 years
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intermittant fault in central locking system of my 3 Series

Customer Question

intermittant fault in central locking system of my 3 Series 1999. Sometimes it works ok and when it does'nt I unlock drivers door with key but other three doors remain locked. Is the fault in the drivers door? What do you think please.
Submitted: 4 years ago.
Category: Car
Expert:  Matt replied 4 years ago.
Hello

1st thing to do is replace the battery in the key fob

and if that doesn't help then I'd try resetting the ECU by disconnecting the battery cables and clamping them together for 10 mins. Remove both battery leads from the battery then use a nut and bolt or G-clamp to hold both battery lead terminals together.

This discharges any capacitors / memory within the ECU and around the car so ensures all memory settings are wiped clear - back to the factory default.

This will reset all the systems on the car and you may need the radio security code to get it going again, and ensure that the keys are in your hand when you re-connect the battery as the car may lock and turn on the alarm