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C O P

posted May 31, 2016 07:40:41 by CyrusKiur
Hey,I have nissan b15 and the pcm doesn't control ignation coil number 3.the coil has 3 wires,one for power 12 volt,second ground and third control wire from pcm.the pcm sends 4 volt on control wire.wen i unplug the coil connetor i see 4 volts on control wire,wen plugged in 1.3 volts.according to Paul danner,says wen u get voltage on control wire u pull down the voltage and u get the sparks.if zero volt on control wire pull up.now y pcm is pulling down the 4 volts wen connector plugged in?and no sparks?
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10 replies
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IvanKibuka-Kiguli said May 31, 2016 10:54:22
Perhaps because the coil is shorting the control wire? What do you find on the control wires of the known good coils?
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CyrusKiur said May 31, 2016 12:05:29
No shorted coil,have replaced them all.socket uplugged 4.48 volts plugged in 1.38 volts.
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Chris said May 31, 2016 14:38:18
Can you scope the signal wire and see if it's moving up or down in voltage. I'd think there wouldn't be any voltage on the signal wire until it was time to fire the coil. Unless it's a pull down circuit but you'd have no voltage on the signal wire unplugged. Coil current ramp may help too
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IvanKibuka-Kiguli said May 31, 2016 14:47:19
If ever there are cases when a DSO makes life much easier, this is one of them. I agree with Chris's advice. If scoping at coil shows no signal, repeat at PCM to confirm or eliminate a broken signal wire/bad PCM. Paul, is this a scenario where one needs to be careful attempting a by-pass test by creating a signal using a test light? Can cook the driver?
[Last edited May 31, 2016 14:55:01]
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CyrusKiur said May 31, 2016 16:49:08
Have scoped and no control at all on the control wire.i think paul danner says to test the control wire socket plugged in not unpluged.socket plugged in i should see 4 volt on control wire(pull down curcuit)0 volt socket pluged in(pull up circuit)right?I think the problem is pcm,have checked the control wire from another same car and no volt at all socket unpluged/plugged in.I think pcm chip that controls coil is shorted.
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CyrusKiur said May 31, 2016 16:54:58
Hope the pcm is sending fake volts on control wire the chip that controls coil is shorted.I can see some black spot on the chip.but still i nid more information abt how to test coil and how to know whether is pull up or pull down.should check voltage on control wire socket plugged in or unpluged?
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Dylan said May 31, 2016 17:36:49
Hope the pcm is sending fake volts on control wire the chip that controls coil is shorted.I can see some black spot on the chip


You mean you opened the PCM?
Belgium, Europe
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CyrusKiur said May 31, 2016 18:03:30
Ofcourse,it simple to open
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Dylan said May 31, 2016 20:56:18
But is it simple to fix ;-)
Belgium, Europe
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CyrusKiur said Jun 01, 2016 07:08:20
Have to replace the pcm
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