CKP signal flopping from capture to capture

tintoverano · Post by **tintoverano** » Wed Oct 04, 2023 1:11 pm

hi,

I got these waveforms from a series of captures starting on a cold engine and as you can see the CKP signal is flopping between the two

I made roughly ten captures and I got 2 or 3 times when the CKP signal flopped like that

no change on the scope or leads, etc. at all between the captures - only engine temperature

ideas for the flops happening?

thanks!

Rfmotors1 · Post by **Rfmotors1** » Wed Oct 04, 2023 1:41 pm

Hi tintoverano,

Very interesting capture, as per my experience, it is faulty sensor but I have seen videos about magnetised pick up ring which causes the flip. See the link here:

https://youtu.be/SCqPkceWL9o?si=JwPUREww3AC0ypNx

I have never seen magnetised pick up personally.

Also, are you able to post the waveform file here? I would like to show it on training class.

Regards,
Roman

tintoverano · Post by **tintoverano** » Wed Oct 04, 2023 1:50 pm

hi,

this is my first too, if magnetism plays its magic here

I saw that video, thanks!

files are large for upload, but here're the links to them

https://drive.google.com/file/d/1O3VSA2 ... sp=sharing

https://drive.google.com/file/d/1O6cdjm ... sp=sharing

tintoverano · Post by **tintoverano** » Wed Oct 04, 2023 2:00 pm

in my case the CKP signal stays in its original state during the whole capture, it doesn't flip-flop during one run

Rfmotors1 · Post by **Rfmotors1** » Wed Oct 04, 2023 2:17 pm

Thank you very much for the files, I have downloaded and will check them.

Definitely update us here with your findings as its really interesting case.

Regards,
Roman

Rfmotors1 · Post by **Rfmotors1** » Fri Oct 06, 2023 7:09 am

Hi tintoverano,
I have looked at your waveforms and tried to get some logical answer, as this is very interesting topic.
I am also assuming there is no complain from customer and no DTC or any warning light.
The main question is what should we do when we get such reading, replace some part as this may be the last stage of component before it fails? or let it go because there is nothing wrong?

1- Can it be damaged pick-up ring? dirty or magnetised? Can the properties change by temperature?
2- Could it be faulty sensor?

Here is what I have observed when I have overlayed both crankshaft sensor signals. They are also synchronised with help of cam sensor to set them to current position. The result is they are both identical except the first rising edge is different, it will be easier to see the pictures with some notes.

Let’s focus on the falling edges as described on following picture.

My guess is the rising edge is advanced due to faulty sensor, the fact there is no problem yet does not mean it is normal and will not cause trouble in near future. But that is just my guess.
I also think the damaged pick-up wheel would have permanent effect as well as some metal chips on the pick-up wheel.

It would be fantastic if someone else could put more light to this.

Once more, thank you for bringing this up tintoverano.

Regards,
Roman

Rfmotors1 · Post by **Rfmotors1** » Thu Feb 08, 2024 3:48 pm

Hi Pico community,
Anyone has any comment to this unusual behaviour discussed above? I am very curious and would like to know if my theory is plausible or not.
Also we can all get prepared for such scenarios.
Thank you,
Roman

tintoverano · Post by **tintoverano** » Fri Feb 09, 2024 7:58 am

Rfmotors1 wrote: ↑
Fri Oct 06, 2023 7:09 am
Hi tintoverano,
I have looked at your waveforms and tried to get some logical answer, as this is very interesting topic.
I am also assuming there is no complain from customer and no DTC or any warning light.
The main question is what should we do when we get such reading, replace some part as this may be the last stage of component before it fails? or let it go because there is nothing wrong?

1- Can it be damaged pick-up ring? dirty or magnetised? Can the properties change by temperature?
2- Could it be faulty sensor?

Here is what I have observed when I have overlayed both crankshaft sensor signals. They are also synchronised with help of cam sensor to set them to current position. The result is they are both identical except the first rising edge is different, it will be easier to see the pictures with some notes.
Overlayed Crank WF.jpg

Let’s focus on the falling edges as described on following picture.
Overlayed Crank WF detail 3.jpg

My guess is the rising edge is advanced due to faulty sensor, the fact there is no problem yet does not mean it is normal and will not cause trouble in near future. But that is just my guess.
I also think the damaged pick-up wheel would have permanent effect as well as some metal chips on the pick-up wheel.

It would be fantastic if someone else could put more light to this.

Once more, thank you for bringing this up tintoverano.

Regards,
Roman

hi,

somehow I missed your post
I didn't find anything further, also it was a mobile diag

thanks for looking at the captures!

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