I am a Ford tech...as such when I have seen P0606 on Ford products it is generally caused by RF (radio Frequency) interference. The most common cause for this that I have seen is a faulty coil although I have repaired this by replacing the alternator in a few vehicles as well. You could try swapping the coils with another vehicle to eliminate that and just unplug the alternator(power cable included) and drive to see if the problem still exists.
As I said my experience is with Ford products and this may not apply but who knows
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