Citreon C5 P0351 code

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Citreon C5 P0351 code

Postby Liteace » Thu Nov 22, 2012 10:11 pm

Not a major find compared to what you other guys find and post on here but thought I'd put it in as i quite happy with the outcome

Got in a Citroen 2001 C5 2000, 16v (RFN) owner said its been to 2 workshops, 1st workshop fitted a new coil, 2nd workshop said it needed a new coil, owner complained of a hesitation + a yellow lamp flashing up on dash when driving and every now and again at idle depending on how far \ long the car had been driven for, mil (yellow lamp) would go out after stopping & restarting engine. I plugged in diagbox done a scan and got a P0351\2 Ignition Coil A Primary/Secondary Circuit Malfunction,

1st thing was to check compression, change plugs & check "new" coil, Compression was good, plugs fitted didn’t look to old & coil was good. Fitted new plugs & cleared the codes, let it idle for 10 \15 mins, no mil, I gave it a 10 min drive, slight misfire, on come the mil again, same codes appeared, stopped restarted the engine mil off, let it idle while sitting in the car and looking at live data, the data stream was a little slow, I was waiting for the misfire, when it did misfire I got this:


c55.png



Time to get the Pico out.

Chan A, Primary
Chan B, Coil current
Chan C, Coil feed:

as you can see it dont look to bad for an 11 year old car, Zoom in on the green trace and you can see a just under 300mv voltage drop for just over 3ms as the coil is charging.

C5 coil FOgif.gif

C5 coil FO.psdata
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Sitting looking at screen waiting for misfire not a lot happened, I then got a slight misfire, I stopped the scope went back and found this:

C5 fan startinggif.gif

C5 fan starting.psdata
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After waiting and checking I then realised this misfire was happening everytime the cooling fan started, you can see a little difference there, coil feed (chan C) has dropped from 14 volts down to just under 12v, Chan B current has dropped from 8.7 to 6.2 amps, I switched off Chan A & B, slowed everything down and waited for the fan to start again, you can see nearly a 3 volt drop for just under 3 sec's on the coil feed when the cooling fan starts:

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C5 fan.psdata
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Next was to amp clamp the fan feed using the 60amp clamp:

C5 fan amps.psdatagif.gif

C5 fan amps.psdata
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you can see its off the screen, I clamped the feed again with the 600 amp clamp, set on 100-200 amps + Chan C on coil feed:

C5 fan amps3.psdatagif.gif


C5 fan amps3.psdata
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when the fan starts its drawing neary 110 amps, 1st thought was bad fan motor or bad battery, I put a good battery on just incase, I also checked the fan was spinning nice and free with no noise. I plugged in Diagbox again, selected actuator test, 1st was to check the high speed cooling fan, that worked, next was low speed fan, that didnt work, I checked all wiring, relays and fan resistor & found the thermo fuse in the fan resistor had melted

If the fan started on the lower speed then switched to high when needed it would no have been supping that much current & causing the missifre. I have ordered a new fan resistor, when thats in and fitted I'll check current draw and voltage drop again but Im 100% sure that will solve the problem

I may have if I'd used my brain realised that the cooling fan starting on full speed is going to draw lot of current but its better to use the Pico and be 100% sure + it helps save what little brain I have left :shock:
Last edited by Liteace on Sun Dec 02, 2012 1:11 pm, edited 9 times in total.
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Re: Citreon C5 P0351 code

Postby antthecat » Thu Nov 22, 2012 10:44 pm

Very nice find buddy.
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Re: Citreon C5 P0351 code

Postby Robski » Thu Nov 22, 2012 10:54 pm

Not a major find compared to what you other guys find and post on here but thought I'd put it in as i quite happy with the outcome


Nowt wrong with that :wink:

Edit the study to include pictures as well as the files :wink:
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Re: Citreon C5 P0351 code

Postby Liteace » Thu Nov 22, 2012 10:58 pm

Robski wrote:
Not a major find compared to what you other guys find and post on here but thought I'd put it in as i quite happy with the outcome


Nowt wrong with that :wink:

Edit the study to include pictures as well as the files :wink:



How do I do that ???

Thanks
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Re: Citreon C5 P0351 code

Postby Robski » Thu Nov 22, 2012 11:27 pm

Save the captures in Pico as gif rather than a PSD file ;)
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Re: Citreon C5 P0351 code

Postby Liteace » Sat Nov 24, 2012 5:23 pm

Fitted 2 new fan resistors, 1 is for the AC and other for engine cooling, I selected actuator tests in Diagbox, done a high speed fan test, with the new resistors the fan start off slow for for about 10 secs and switches to full speed, I also done a a low speed test and that is also working as it should. Gave the car a good long drive up a nice long steep hill while switching AC on and off and its all fine, I wanted to grab some scope screens BUT when I tried to run the XP partition on the PC that has the Pico software

I got: missing \WINDOWS\SYSTEM32\CONFIG\SYSTEM error message,

I'll try and sort this problem out over the weekend and see what I can grab on Monday.

Im real happy with the outcome of this one, who would have belived that a faulty fan resistor would have caused a P0351\2 code, I honestly think if it wasnt for the power of the Pico I would be still head scratching now :D
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Re: Citreon C5 P0351 code

Postby Darren Cotton » Sat Nov 24, 2012 7:07 pm

I have seen the resistor issue before, but never shown a fault as described. Interesting post, and nice find, one to consider before jumping in feet first....

Well done


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Re: Citreon C5 P0351 code

Postby Dave Hill » Fri Dec 14, 2012 8:37 pm

Great Post!

On the face of it, I would have thought that you were looking at an intermittent short in the primary windings or something similar.

This shows that not only do you need great tooling, but also a great instinct for this kind of work. Pico or not, It would be so easy to overlook the possibility that the fault coincided with the fan activation.

Great use of your channels to study crucial elements of the system.

I have actually modified a few faulty cooling system fan setups, so that they are either off or on 100%, rather than slow start. Now I have seen this, I will consider the consequences before manipulating the manufacturer design.

It would be nice to see some "post repair" waveforms though, if you can sort your system.

Take a bow Inspector Clouseau :D

Image

Seriously well done!
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Re: Citreon C5 P0351 code

Postby Liteace » Sat Dec 15, 2012 11:36 am

Dave Hill wrote:Great Post!

On the face of it, I would have thought that you were looking at an intermittent short in the primary windings or something similar.

This shows that not only do you need great tooling, but also a great instinct for this kind of work. Pico or not, It would be so easy to overlook the possibility that the fault coincided with the fan activation.

Great use of your channels to study crucial elements of the system.

I have actually modified a few faulty cooling system fan setups, so that they are either off or on 100%, rather than slow start. Now I have seen this, I will consider the consequences before manipulating the manufacturer design.

It would be nice to see some "post repair" waveforms though, if you can sort your system.

Take a bow Inspector Clouseau :D

Seriously well done!


Thanks, unfortunately I just didnt have time to sort laptop before it had to go back, the lappy is now all up and running again, when this vehicle does come again for whatever I will grab some waveforms from it
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Re: Citreon C5 P0351 code

Postby DaveF » Sat Dec 15, 2012 3:43 pm

What a top notch lesson in diagnostic procedures and thought process. Not everyone would have spotted that, even if they had also used Pico. Great post.

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