hi guys, I recently scoped a cop 3 wire design coil, I was connected to the power feed using my amp clamp on channel A and connected to coil control using test leads on channel B, (luckily I used attenuator - you will see why) I was under the impression that the transistor for the coil was internal to the cop and the ecm produces a 0-5v approximately turn on signal to activate and start ignition, dwell time dependant on ecm,the coil having a ground, 12v feed and a signal, well please find attached a copy of the waveform, as you can see the signal wire is not a 5v turn on control via the ecm but actually as I see it the primary coil ground, this proven by seeing a primary ignition waveform, I will attach the diagram of the circuit and waveform, any input on this design would be great.
As seen in this wiring diagram which is from a Citroen 1.6 litre engine code ( EP6CDTX ), it's clear, that the primary ignition system are turned on and off inside the ECU and not at the ignition coil (COP).
You used the attenuator on the picoscope which seen hindseided was wisely done if you dont know circuit in details.
Thanks for both your replies guys, it appears it actually is quite common, I just haven't personally ever come across this before and was a little surprised, another circuit design to add to the memory bank!