With my experiences on M cars. Best would be to get rid of it now, back to BMWNA. I did that in South Africa with an E60 M5. The car just either switched off at anytime or refused to start? was brand new, not even run in yet. The engine was perfect, it's the ECU, M-DME & only God knows which computer link just keeps on failing. Once all their investigations were completed (4 weeks) BMW-SA, replaced me with a brand new M5. I was also given a loan 550i at the time for the gross inconvenience. P.S. They never truly found the problem & the M5 was apparently shipped back to Germany, so I was told?

So honestly if your problem persists, insist on your money back or a brand new M.

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1988- M5 E28 Full South African Spec Antracite
2000- 740i E38 Fully Loaded Sorrent Blue
2004- 730d E65 Fully Loaded Titan Silver
2008- 750i E65 Fully Loaded Black
2005- 530d E60 Fully Loaded Deep Green
2009- 330d E90 Sport Pack Fully Loaded T/Silver
2009- X5 3.5d E70 Sport Pack Fully Loaded
Titan Silver