Romeo might be right, I recently had a similar problem on my e46, and it was the GM5 module. I sent it off to be repaired, and it fixed all of the key fob unlock/central unlock button/fuel door unlock issues that I had been having.

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2007 BMW X5 4.8i - Sport Package, Wife's Car

2001 BMW 325i - My Car.

2005 Ford Excursion Limited 4x4, 6.0 Powerstroke Diesel. My first "grown up" car.