Signal noise on cam sesors BMW E87

Ask for and share advice on using the PicoScope kit to fix vehicles here.

Signal noise on cam sesors BMW E87

Postby bonecrusher » Thu Oct 20, 2016 9:18 am

Hello Guys

I am working on this BMW e87 with N46 engine I have signal distortion on the cam patterns , what causes this?
Attachments
BMW 1 series E87 exhaust camshaft N46 crank and 2 cams.png
bonecrusher
User
User
 
Posts: 15
Joined: Wed Mar 16, 2016 2:34 pm

Re: Signal noise on cam sesors BMW E87

Postby STC » Thu Oct 20, 2016 12:36 pm

Is this a Petrol 4 cylinder Direct Injection ??
I'm guessing its the Coils Multi Striking and wondering where your scope leads are routed.

That distortion is possibly nothing to worry about. The ECU will either not see it or ignore it.

Could you post the File Please, better still take another capture with Crank, Ignition Primary Cylinder 1 and Injector 1 at idle and post that. (Cold Engine)

What are the Symptoms / Fault Codes ?
User avatar
STC
Zen Master
Zen Master
 
Posts: 369
Joined: Sun Sep 13, 2015 2:10 am

Re: Signal noise on cam sesors BMW E87

Postby FioranoCars » Fri Oct 21, 2016 12:32 pm

STC wrote:That distortion is possibly nothing to worry about. The ECU will either not see it or ignore it.

I agreee, but it could be the spacing of the sensor is at the max, check the spec for spacing and face of the sensor for damage/debriss ... or it could indicate an out of true phonic wheel, or at least a slightly bent one ... Even float on the shaft (crank) as it moves. But not enough to cause concern right now, unless it's getting worse, then might be good to know which it is. Adding a voltage reading (at the sensor) might shed some light, as might earth if there is an earth problem (highly unlikely though).

Saw this, much worse definition - ie massive dips, on an Alfa that had been put back together by complete idiots, and the phonic wheel was bent, sadly the phonic wheel was the least of the problems, the engine was a box of spanners. Owner said he'd driven it the day before just fine ... yes, absolutely sir!! Dumb A55!

Be nice to know what you find for the sensor, and why you were looking at it.
Best to post the capture files for anything you want looked at so we can see the raw data.

STC wrote:What are the Symptoms / Fault Codes ?

Ditto

Good luck
Richard
User avatar
FioranoCars
Zen Master
Zen Master
 
Posts: 288
Joined: Thu Dec 13, 2012 11:26 am
Location: London, UK

Re: Signal noise on cam sesors BMW E87

Postby STC » Fri Oct 21, 2016 3:03 pm

Looking at the rise and fall of Crank sensor amplitude, the interference appears to line up with where I would guess injection/spark events could be. This is Direct Injection, right ?
Add to that the events occur 4 times per 720 of the crank or 360 of each cam and evenly spaced.

Hence I asked for the additional traces. Cold Engine as that is where multistrike will occur.
User avatar
STC
Zen Master
Zen Master
 
Posts: 369
Joined: Sun Sep 13, 2015 2:10 am

Re: Signal noise on cam sesors BMW E87

Postby bonecrusher » Tue Oct 25, 2016 7:07 am

Hello Guys

Thanks for all the feedback. I am still new to the pico. Although I have it for a while now. I only used 5 times maximum. Back to the topic discussion. I used sensor ground connected to the PICO and all noise/interference is solved.
bonecrusher
User
User
 
Posts: 15
Joined: Wed Mar 16, 2016 2:34 pm

Re: Signal noise on cam sesors BMW E87

Postby FioranoCars » Tue Oct 25, 2016 8:49 am

Hi, and thanks for posting back an update

Was there a reason for the test, or just curiosity and having a play with Pico (ie was there a fault on the car)?

Do you have a saved Good waveform? Maybe you can upload it to the Pico waveform library, with a note about the noise when taking the ground from elsewhere?

Richard
User avatar
FioranoCars
Zen Master
Zen Master
 
Posts: 288
Joined: Thu Dec 13, 2012 11:26 am
Location: London, UK

Re: Signal noise on cam sesors BMW E87

Postby STC » Tue Oct 25, 2016 6:58 pm

I used sensor ground connected to the PICO and all noise/interference is solved


You don't make it clear where you had the scope Earth on the original capture, even more bewildered with what "Sensor Earth" is ? Have you gone from Battery to the Earth on the 3 Sensors ??
I know that DLC Pin 4 is "Chassis Ground" Pin 5 is "Sensor Ground" but that is a nonsense with most cars as they are wired together and always to an Earth Point on the Chassis / Body

I still think that interference is real, moving the earth has only masked it, I still maintain it is unlikely to affect the car. A quick calculation suggests that it is running at ~ 1000rpm

The interference is too regular, 5 spikes each time and always as a piston is at / near TDC from my reckoning.
User avatar
STC
Zen Master
Zen Master
 
Posts: 369
Joined: Sun Sep 13, 2015 2:10 am

Re: Signal noise on cam sesors BMW E87

Postby FioranoCars » Tue Oct 25, 2016 7:13 pm

Subject: Signal noise on cam sesors BMW E87

STC wrote:
I used sensor ground connected to the PICO and all noise/interference is solved


You don't make it clear where you had the scope Earth on the original capture, even more bewildered with what "Sensor Earth" is ?


Hi George
Ok, I am guessing BoneCrusher is referring, just as I would ( :oops: !!), to, for instance on a hall effect sensor sensor of typically 3 wires ...
1. supply (+12v)
2. ground (chassis)
3. Signal (often shielded)

So maybe he's saying he probed the ground wire on the connector at the sensor, second time round, verse the initial test where some chassis or worse some engine part was used!

Of course normally the engine ECU is supplying (or some near chassis point to the ECU) the ground, and if using the engine direct for the scope earth there will be a lot more noise (and possible volt drop over the earth strap(s) to the chassis).

The new 4 series floating earth's have great benefits, but also can cause confussion too...

Sorry to semi-answer for you BoneCrusher, I'm not really, honest!
Please do tell what happened, it's so we can all learn. And why you where checking it?

Thanks
Richard
User avatar
FioranoCars
Zen Master
Zen Master
 
Posts: 288
Joined: Thu Dec 13, 2012 11:26 am
Location: London, UK

Re: Signal noise on cam sesors BMW E87

Postby STC » Tue Oct 25, 2016 8:13 pm

Please do tell what happened, it's so we can all learn. And why you where checking it?


x2
User avatar
STC
Zen Master
Zen Master
 
Posts: 369
Joined: Sun Sep 13, 2015 2:10 am


Return to Diagnostic discussion

Who is online

Users browsing this forum: No registered users and 1 guest