620i coil problems

[jsalvat]

I have a 620i and this the fourth set of coils I have replaced I have a tech manual and keep getting error codes 51 & 52 replaced coils with new ones will still not start in the past after changing coils it would start again but not this time any one have same trouble I am thinking of replacing control unit . any ideas would be welcome !

JIM

[jsalvat]

well looks like I fixed the problem myself by taking one of the coils off to test with an ohm meter to see if they were defective tested ok re installed tried to start and it:Ysnd: started
must not have a good connection