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I'm actually having a similar issue with my plug and play but was waiting to worry about it until I had to. So subscribing for other potential assistance.
So I looked at mine. I have the same issue. Speed bounces from 100km to 200km. Its all over the place. I didn't notice this with V13 or older. Wondering if this is a V14 thing?
I have the same issue. I came to realise this when I used the launch control the first 1st time. Set it to be disabled over 4km/h but once i got going it was limiting even above the set seed. Checked the logs and it was allover the place 0,20,230,100 etc....
I haven't work on an FC before, so I haven't encountered this speed signal fluctuation yet. But looking at the factory diagram, I see two possible things that may cause the noise. One is that the actual sensor is a reed switch. For those who are not familiar, you can check this link - https://en.wikipedia.org/wiki/Reed_switch
The problem with a reed switch is that the two contacts actually bounce a bit when they close - like when you drop something on the floor it doensn't usually go splat. That will cause some high frequency noise, and although we have some filtering available in the ECU, it still has to work with systems with normally high frequency inputs like ABS sensors so we couldn’t filter out enough for the reed switch contact bounce. Another thing that might cause the noise is that the reed switch uses the chassis ground (i.e. not a sensor ground) which we want to avoid because those grounds are usually noisy. So after talking to Andy, he suggests to put a 100nF capacitor between the VSS input and SGND (sensor ground) and see if that helps.
The FD should be different though i.e. doesn't use reed. For the FD guys who has this problem are you getting the speed signal from the factory location?
I'm nearly to the point on my s5 t2 where I actually will be worried about this and will attempt the suggested capacitor but it may be a while til I get around to it.
With the reed switch wiring as is stock my speed numbers are virtually random.
Same problem with a FD S6 pnp ecu in a FC. I will try a capacitor and report back!
I tried 10 and 100 nano. Both do the job of removing the really unplausible values from the speed signal. Still even with the 100 nano the signal has noise on it, like +-2 km/h approx.
I too have an update on this. It seems that I managed to fix the issue by replacing my cluster with 1 in better condition. I think that anyone with issues can start by checking the printed circuit on the rear of the cluster.
I too have an update on this. It seems that I managed to fix the issue by replacing my cluster with 1 in better condition. I think that anyone with issues can start by checking the printed circuit on the rear of the cluster.
Okay, but I think at this time finding a mint FC cluster that hasn't even has a little noise in the contacter will be kind of a miracle for most of us.
If you look on the screenshots of the scope I posted, even without the cap the noise is really minimal and I feel the processing of the signal should not be rocket science to let it work.
I do not know how the signal processing is at this time, but if there would just be a comparator with a voltage threshold of 1.5v for example (depending on the pull up voltage). then it should work 100% fine even without adding a cap.
Okay, but I think at this time finding a mint FC cluster that hasn't even has a little noise in the contacter will be kind of a miracle for most of us.
If you look on the screenshots of the scope I posted, even without the cap the noise is really minimal and I feel the processing of the signal should not be rocket science to let it work.
I do not know how the signal processing is at this time, but if there would just be a comparator with a voltage threshold of 1.5v for example (depending on the pull up voltage). then it should work 100% fine even without adding a cap.
Sure but I was referring to FDs. Sorry if it wasn't clear.
Interesting to hear about the cluster part, as I didn't have any problems with my speed reading fine on the adaptronic. But I recently changed my motor mounts and for some reason the odometer and trip part went out and now the speed on the adaptronic is erratic as hell.
Interesting to hear about the cluster part, as I didn't have any problems with my speed reading fine on the adaptronic. But I recently changed my motor mounts and for some reason the odometer and trip part went out and now the speed on the adaptronic is erratic as hell.
There is a harness from your transmission that deals with all this. Speed and odometer is from the transmission. There are three(?) plugs on the tranmission side, easily accessible if you are under the car. This harness is independent of your ECU, likely kinked? broken? knocked loose? when you changed your motor mount.
It goes from the transmission to the same ECU opening in the firewall, and connects under the passenger side dash.
Off the top of my head I think it is a blue connector in the cabin.
Last edited by silentblu; 06-03-17 at 07:19 PM.
Reason: Added info.
08-27-16, 12:17 PM
