abnormal cop 3 wire circuit design

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colley390
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Posts: 2
Joined: Thu Aug 03, 2017 12:18 pm

abnormal cop 3 wire circuit design

Post by colley390 » Wed Dec 27, 2017 11:58 pm

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.

pin 1 - coil control
pin 2 - coil ground
pin 3 - 12v
Attachments
cop control wire and current ramp.png
cop control and current ramp

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Tronic
TwoWaves
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Posts: 88
Joined: Fri Oct 23, 2015 2:43 pm
Location: Sweden

Re: abnormal cop 3 wire circuit design

Post by Tronic » Fri Dec 29, 2017 1:07 am

Hi colley390!

Have a look at attached file with a 3 wire COP from a BMW E46 as an example. Did also put some text on how it works.

Regards

Bjorn
Attachments
BMW COP Picoauto.JPG

KimAndersen
TwoWaves
TwoWaves
Posts: 206
Joined: Fri Nov 30, 2012 2:53 pm
Location: Denmark

Re: abnormal cop 3 wire circuit design

Post by KimAndersen » Fri Dec 29, 2017 12:01 pm

Hi

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.
CITROEN_EP6CDTX_16L_COP_SYSTEM.jpg
CITROEN EP6CDTX 1.6L IGNITION SYSTEM
Regards
Kim :wink:

colley390
Newbie
Posts: 2
Joined: Thu Aug 03, 2017 12:18 pm

Re: abnormal cop 3 wire circuit design

Post by colley390 » Fri Dec 29, 2017 8:38 pm

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!

kind regards ryan :wink:

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