My 2007 r56 just had a new head put on and now it has no spark and cranks but won’t start. Using a snap on scan tool it will read all the codes but can not communicate with the engine. The codes I do get are. C310, a0b3 and a0c1

 

check the connections to the DME and check the ground wire on the valve cover. Lastly, check the relays next to the DME.

 

Ground wire like MINITOBE mentioned, also check that ground wire on the passenger side motor mount bracket.