No signal to Ignition Coil 4

Hello

Solid Lane B light for the last 5 hours.  Initially it would clear only temporarily for a couple of seconds after turning Lane B master switch off and then on again, and during those few seconds the engine increased rpm by around 100/min.  Now Lane B light doesn't clear even for a few seconds after turning Lane B master switch off and then on again.  Dynon Skyview 'faults' annunciation:- 'Ignition Coil 4".

No spark at all visible at the two plugs that are fed from Ignition Coil 4 when cranking engine over in a dark hangar whereas spark is visible at all other 6 plugs fed from the other three ignition coils.

I replaced ignition coil 4 with a new coil but that didn't fix the problem.

I tested resistance with multimeter of both high tension leads from Coil 4 and both are okay.

I checked spade terminals at Coil 4.  They were clean.  Applied dialectic grease and that didn't fix the problem.

I've come to conclusion that the problem is not the coil or anything 'downstream' of the coil (high tension leads or spark plugs), but the problem is upstream of Ignition coil 4 (ie between the ECU and the coil).  It seems to me there's no signal being sent from Lane B ECU to Ignition Coil 4. 

Is there anything else I can check upstream of Ignition Coil 4 that might be the problem?  Is there a fuse or relay that could be at fault?

Any ideas would be appreciated.

Thanks.

Brad Zanker