detected value reading means for reading said detected ion current value, held in said hold means, immediately before starting {HEAD ~ electrical energization} of {TAIL ~ said ignition coil}; and 
of
detected value reading means for reading said detected ion current value , held in said hold means , immediately before starting { HEAD ~ electrical energization } of { TAIL ~ said ignition coil } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH