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Over-sensitive DSC but no codes

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Static
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Over-sensitive DSC but no codes

Post by Static » Thu May 05, 2022 6:38 pm

I wonder if anyone can help because I cant decide what to do next.   

I have an E85 06 3.0SI where the DSC keeps kicking in under normal acceleration.  Im getting no codes on the DSC (or anything related across the other modules) either via ISTA or AUTEL OBD dongle. Most posts seem to suggest wheel sensors, ive replaced one that was erroring and they all seem to read fine when monitoring their behaviour whilst driving

To turn back the clock .....the issue started Christmas Day, driving cross country for xmas dinner, when i got the dreaded orange trifecta.  I didnt have my laptop with me, managed to get to my destination, called out RAC over the xmas break who reset my codes (DSC module and rear wheel sensor)

Test drove the car and all was fine and the car got most of way back home, before starting to do the overactive DSC thing.  I got home, plugged in ISTA and car was again throwing just Rear Left Wheel Sensor Plausibility. 

I didnt have a wheel sensor so - had a look at sensor wiring - which seemed ok but reluctor ring was coated in what looked like plastic and some debris in the slots, but nothing crazy.  I cleaned the ring thoroughly so it was shiny and refitted the old sensor.  Cleared codes, and ta-da everythign was fine

...for about 50 miles.  now im getting the same over active DSC ...but havent had any codes since.  Ive been living with it as im not really using it much and it behaves more or less fine with the dsc partially off
    
Ive since....
  • replaced the rear left sensor
  • got a OBD dongle that has a live feed, and ive checked all the speed sensors and all seem to be reading normally (ie all wheel speed sensors seem to read roughly the same value - none drop to zero or read erratically)
  • recalibrated the steering (steering sensor also seems to behave as expected on the live feed)
  • yaw sensor appears to behave fine - ie not cutting out when im getting the dsc light and values seeeeem to represent what happening in the car
Unusual behaviour
  • Using the live sensor feed - ive been monitoring the overactivity (getting DSC to come on under normal driving) - as i mention above i see nothing obvious across the sensors.  However under hard acceleration or if the DSC kicks in repeatedly (like in motorway driving) then it seems as if everything resets!!!  The DSC light flashes repeatedly and all the sensors read "n/a", and the car basically goes into limp mode for a few seconds (though its tough to tell if its limp mode or just cutting out under DSC anyway).  After a couple of seconds all the sensors read normally again and it goes back to normal over-active behaviour
  • The brake pedal pressure sensor always seem to read 1 bar (not sure if this is normal ) - but overwise behaves normally under normal braking
  • Even with DSC partially off - its still sensitive in specific circumstances - and I get the DSC coming on occasionally but only when accelerating with hard steering (not necessarily aggressively - ie turning into a 90 junction)
  • On replacing the wheel sensor i was getting some rubbing for a couple of miles on uneven roads - suggesting maybe the reluctor ring has corrosion underneath but i couldnt spot any through the little hole
So im wondering what next 
  • Replace all the wheel sensors / new reluctor rings (im a little 'reluc'tant (sorry) to do this as they all seem to read fine)
  • Second hand / refurbed abs module
  • possibly Yaw sensor (though facelift ones are hard to get hold of)
Wondering if anyone has encountered something similar OR has any ideas why im not getting codes any more.  thanks in advance 

TL;DR -  DSC keeps kicking in under normal acceleration.  Im getting no codes
‘06 3.0 Si Roadster

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enuff_zed
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Over-sensitive DSC but no codes

Post by enuff_zed » Thu May 05, 2022 7:00 pm

I have just encountered exactly that issue.
Turns out the DSC wasn't over sensitive at all. I discovered the rear shocks were the original 2003 ones, with 112k on them. As far as keeping the rear wheels in touch with the floor I may as well have had two sticks of rhubarb in there.
A radical thought, but maybe it is telling the truth. :wink:
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Over-sensitive DSC but no codes

Post by Static » Thu May 05, 2022 7:11 pm

enuff_zed wrote: Thu May 05, 2022 7:00 pm I have just encountered exactly that issue.
Turns out the DSC wasn't over sensitive at all. I discovered the rear shocks were the original 2003 ones, with 112k on them. As far as keeping the rear wheels in touch with the floor I may as well have had two sticks of rhubarb in there.
A radical thought, but maybe it is telling the truth. :wink:
Many thanks for the reply - its a good shout

I do need new rear dampers one has started leaking after this issue occured, but this is super severe - ie i cant get to 30 in a straight line, with very judicious acceleration, without it kicking in

Was yours like that?
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Over-sensitive DSC but no codes

Post by enuff_zed » Thu May 05, 2022 7:21 pm

Static wrote: Thu May 05, 2022 7:11 pm
enuff_zed wrote: Thu May 05, 2022 7:00 pm I have just encountered exactly that issue.
Turns out the DSC wasn't over sensitive at all. I discovered the rear shocks were the original 2003 ones, with 112k on them. As far as keeping the rear wheels in touch with the floor I may as well have had two sticks of rhubarb in there.
A radical thought, but maybe it is telling the truth. :wink:
Many thanks for the reply - its a good shout

I do need new rear dampers one has started leaking after this issue occured, but this is super severe - ie i cant get to 30 in a straight line, with very judicious acceleration, without it kicking in

Was yours like that?
It eventually got to the point where it lit up over bumps, without acceleration.
Yours could be made worse if only one shock is leaking.
Tbh, now you've said that, until you replace them you'll never know.
Its a simple job, about an hour all in, or two if you've not done it before.

Get new top mounts and bump stops too while you're at it. NOT Meyle HD mounts as they knock like crazy.
I just compared a Lemforder one with an original and the only difference is that you can see where 'BMW' has been scratched off the rubber on the Lemforder one.
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Over-sensitive DSC but no codes

Post by Static » Thu May 05, 2022 7:25 pm

Cool - it needs doing anyways. Yeah ive been reading up on it - doesnt look too bad a job

What did you go for? Bilsteins?
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Over-sensitive DSC but no codes

Post by Static » Thu May 05, 2022 7:27 pm

haha - yeah saw people had trouble with the Meyle ones - and were recommending Lemforder. Ill add them to the list
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Over-sensitive DSC but no codes

Post by enuff_zed » Thu May 05, 2022 7:43 pm

I did a like for like replacement with Sachs, but Bilstein B4 are the equivalent. As far as I can tell you pick whichever is cheaper.
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Over-sensitive DSC but no codes

Post by Static » Fri May 06, 2022 1:55 pm

enuff_zed wrote: Thu May 05, 2022 7:43 pm I did a like for like replacement with Sachs, but Bilstein B4 are the equivalent. As far as I can tell you pick whichever is cheaper.
All ordered - shocks, top mounts and boots/bump stops - Thanks for all your help and advice

Is it worth getting new lower bolts? I assume they are standard bolts? (M12X1.5X60 accoriding to RealOem)

Is there anything else you can think of in terms of hardware
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Over-sensitive DSC but no codes

Post by enuff_zed » Sat May 07, 2022 7:39 pm

Static wrote: Fri May 06, 2022 1:55 pm
enuff_zed wrote: Thu May 05, 2022 7:43 pm I did a like for like replacement with Sachs, but Bilstein B4 are the equivalent. As far as I can tell you pick whichever is cheaper.
All ordered - shocks, top mounts and boots/bump stops - Thanks for all your help and advice

Is it worth getting new lower bolts? I assume they are standard bolts? (M12X1.5X60 accoriding to RealOem)

Is there anything else you can think of in terms of hardware
That should be the lot.
Are you talking both ends or just the rear?
On the rear I usually reuse the bolts as no part of them is really exposed so they remain in good nick.
On the front, the lower knuckle pinch bolts corrode as the centre of them passes through the gap in the knuckle, so get new for them.
Got my last pair from here:
https://www.ebay.co.uk/itm/175141185140
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Over-sensitive DSC but no codes

Post by Static » Sun May 08, 2022 9:23 pm

@enuff_zed - just doing the back for now. Thanks will bear that in mind when I do the fronts
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Over-sensitive DSC but no codes

Post by enuff_zed » Sun May 08, 2022 9:25 pm

Static wrote: Sun May 08, 2022 9:23 pm @enuff_zed - just doing the back for now. Thanks will bear that in mind when I do the fronts
OK, well I hope it fixes you problem, but as I said, until you do it you'll never know if it was the issue or not.
I reckon once you've done the rear you'll the difference and soon be on to the front. :D
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Over-sensitive DSC but no codes

Post by Zulu4 » Mon May 09, 2022 8:29 pm

Static wrote: Sun May 08, 2022 9:23 pm @enuff_zed - just doing the back for now. Thanks will bear that in mind when I do the fronts
Did my rear shocks today; here's an easy method of changing them:
viewtopic.php?t=130973&start=19
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Over-sensitive DSC but no codes

Post by Static » Tue May 10, 2022 3:43 pm

Zulu4 wrote: Mon May 09, 2022 8:29 pm Did my rear shocks today; here's an easy method of changing them:
viewtopic.php?t=130973&start=19
Cheers for that - and for the headsup on the gaskets. Assuming they are the ones above the top-mount (33526772864) Just ordered those too.
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Over-sensitive DSC but no codes

Post by Static » Sun May 22, 2022 6:26 pm

Just an update in case anyone else has issue

Fixed it! Was reluctor ring on other side, cleaned the layer of plastic and crud that had built up, and didn’t even change sensor and immediately no dsc lights.

I did also change my rear shocks, they were knackered - could push the leaking one in with my little finger. Were bmw labelled on an ‘06 😱. Not surprisingly has made a significant difference to handling.

Noticed my top mount starting to go on front, but struggling to get front B4s - back order till July/Aug :( :(.

Fortunately they are deffo not orig shocks on front , but might as well change em if doing top mounts.

Might have to mix and match 😒

Will update shortly with my method for cleaning reluctor ring.
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Over-sensitive DSC but no codes

Post by Static » Sun May 22, 2022 7:27 pm

My method to clean ring - I assume it’s a build up of plastic from the sensor and stuff that gets caught between sensor and ring that coats the ring and affects the sensor reading. - to begin with it just looks tarnished it’s only when you start scraping you can see how bad it is. It’s a little like it’s been plasti-dipped with crud

- remove the speed sensor (this might take some time if it’s never been out, go easy with the Allen key, and get yourself some new bolts (M6 x16)
- put a few wheel bolts back in the hub and use something between them to help turn hub - I used an l-shape wheel brace (you’ll obv need front chocked, In neutral and handbrake off)
- Get a mid-sized old screwdriver, as large as you can get in sensor hole but short enough that’s it manoeuvrable in wheel arch. The idea is to rotate the hub and scrape the flat continuous edge of the ring against the turn, without getting the screwdriver caught in the holes in the ring. So try and keep the blade edge flat against the ring - I did this by bracing it in the sensor hole against the side closest to the edge you’re scraping. You don’t need much pressure so if the screwdriver does catch you can release the pressure quickly. You don’t want to damage the ring or worse have the screwdriver spring under tension
-it takes a bit of fiddling but I found it easier to achieve with a larger screwdriver than tiny screwdriver - ymmv - a head torch is very handy
- when I found a good position I could turn/scrape over 180 degrees uninterrupted and although I couldn’t see what was happening it cleaned an edge very quickly
- if you scrape both continuous edges of the ring - all you should be left with is the bits in the middle (each side of the gaps) and with a good sized screwdriver I found it removes a lot of this as you do the edges
- Get a small screwdriver - electrician-ish size , slowly tick the hub round to reveal each ring gap and Individually scrape the remainder. you can feel the hard muck as it’s raised under the screwdriver. So just catch your blade on the edge and lever against the sensor hole you need very little pressure
- obv be careful not to lever against the ring itself either in the gaps or against the edge you should be wholly working on the surface only
- I then scraped out all the gaps with a dentist pick but mine were fine
- I finished off with some wd40 to flush any scrapings and the ring looked like new. You can squirt through bolt hole with a straw (I only realised this after I finished) but I wouldn’t use any fluids until after you’ve scraped

When I did the other wheel - I wasn’t sure what I was dealing with and I used dentist style picks, a little wire brush inserted from the rear of the hub, some emery cloth, brake cleaner and it took ages. The coating did come off in ‘H’ sections that way but took much longer and was very messy, Brake cleaner may not be a great idea either but I used it fairly sparingly. It’s much cleaner doing it dry and you can see what you’re doing easier.

Sorry there’s no pics
‘06 3.0 Si Roadster

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