The PCM/ECU pulses both sides, one is for cylinders 1+4, the other is for 2+3, if you look on the old coil pack, where the damage is will be the side that isn't pulsing. What happens is the high KV that should be sent to the spark plug back-tracks to the PCM and blows the internal circuitry. Both the sensors you mention send signals to the PCM which uses them accordingly.