# 2009 750i misfires and code CD9304 Please Help



## POleary (Feb 18, 2021)

Hi, i have a 2009 750i with misfires, changed spark plugs and coils. still had misfires on # 1,3,4,5. changed injectors still have misfires mostly on #1 cylinder. also after changing injectors i have code CD9304, BSD (Bit-Serial Data Interface) bus communications fault Permanent, code will not clear but no other codes.changed #1 injector again but still have the same problem. Please Help


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## Bmwaudivwdude (Dec 25, 2009)

The screws on the fuel injector/ignition coil harness are ground screws. If you don't use the right ones or mix them up, or if you crank the car without them being in you, will get the BSD code. Check the screws! There is a TSB on it. SI B12 24 14 dated November 2012

Note Misfires on one bank influence the other bank opposite the one cylinder misfiring. Make sure you calibrate the fuel injectors using ISTA D or a professional scan tool. If you don't have a scan tool go to a shop and pay them to do it. Also, sometimes new coils are bad too! I have had this drive me crazy only to find out the new coil is bad. Hope this helps!!!


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