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Matt
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 23957
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Morning, my BMW 335i key fob stopped working, so changed the

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Morning, my BMW 335i key fob stopped working, so changed the battery, but is just the same

Hello

this sounds like you may have lost re-synchronization between the fob and the car try this procedure:

https://www.youcanic.com/bmw/key-programming-resync-procedure

if this doesn't help then 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

then try running through the procedure again

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