Suspension gone harsh since battery disconnect
 

Hello all, had the battery off doing some tests and since re connect the suspension feels harsh like 100 psi in the tyres , no fault codes , suspension lifts up fine and drops back down all good .
Ride hide looks same as usual , jacking / towing mode not engaged , everything seems ok .
Is there some kind of re learns /adaptations to carry out when battery has been off ....... have had it diss connected previously with no troubles though .
Hope it's not spiked the module or something daft

Thanks in advance
Lee

How curious. I've never heard of that before. Sorry, this is no help to you Lee.

Hi Lee,

Sorry to her your having issues, never had any similar problems and I had the batter off a time or two while I owned the car!?

Hope it works itself out!

Paul

I have heard of this before might have been on ross tech forum but cant remember what fixed it, was something simple like disconnecting battery or unplugging module but cant remember or find it again.

its basically the shocks not got power to soften the dampening like the emergency default

I have had this when I first bought the car and read of a couple of others on here - it was always after a flat battery. It always seemed to go away as suddenly as it came, but I would try disconnecting the battery for a few seconds.

Spent hours on this yesterday with vcds ,on further investigation I did think the car sat a little low ,specs for se are 415mm front and 400mm rear ,centre hub to wheel arch ......well to be precise it's 416mm front and 398mm but a couple of mm is hear na there ,mine was sitting at 380mm font 375 rear .
Tried removing battery lead again and a bit of driving round ( will get back to this ! ) , in dynamic mode it was terrible ...... May aswell of been dragged around on a shovel !

http://i618.photobucket.com/albums/t...psdfdliobg.jpg

Coding of level control the double 5 meaning 0 change from base

http://i618.photobucket.com/albums/t...psidoojsju.jpg

Where I was getting a bit lost the double 55 being base I would of thought that in the calibration the desired height would of been 416 f and 398 r but it was not , can't remember what but it was a lower setting , so thought need to get it up to standard ride height so the air bags are at there optimum for a comfort ride , so changed the code to 99 + 20mm , this change got it to nearly factory spec ride height .

http://i618.photobucket.com/albums/t...psb03lbae4.jpg

So test drive at standard ride height ...... it's better for sure but still not as silky smooth as before , I digress .....I took laptop with me on test drive and in comfort mode damping was showing in data blocks as 1.8 amps ... max amps =soft damping , min amps 0.2 amps or some such hard damping setting

When stood still damping is at hard setting , as you get above 10 mph damping reverts to softest setting but watching it on test drive it going from on extreme to the other 0.2 amp ... 1.8 amp sort of cycling effect ..... mmmmm


I was looking through the data and spotted this .....



http://i618.photobucket.com/albums/t...psmvax9azu.jpg


As soon as I saw this I new what was wrong .... strut velocity ..... Eureka !!!

500 SL Mercs with hydractive advance body control suspension have similar .... I've done quite a bit of work on these , they have something called strut measurement rod , it runs through the middle of the strut and measures how it is reacting on the road , if the body battery ever goes flat the damping defaults to a hard setting .
You have to drive them in sport mode ( the hardest damping ) for a good 10 miles or more and the suspension ecm learns how the strut is reacting and dials the damping in , once sport is learned the comfort mode is just a softer map of that .

Are you still here or lost interest and gone to watch the paint drying ........

Back to the a8 ........ so in dynamic mode I set off on test drive maybe after 10 miles of shaking the fillings out of my teeth it starts to get a bit more plush on the ride .... keep driving .... it's getting better by far , switch over to comfort now ...... the plush ride is back to normal ...... it's the ecm learning the strut velocity and dialling it in to the damping map .

Still unsure with the ride height thing , don't understand why the double 5 coding is not the spec ride height , it looks a bit high now so will try it back at that setting .
In reflection I reckon if I just drive the car around in dynamic after I had the battery off everything would of sorted it's self out on its own ..... that's adaptive drive cycle for ya

What I think has happened originally , I had a shunt across the battery doing testing on how much amps is drawn when auxillary hearing kicks in , I was sort of mucking about trying to get a good contact so the battery was kind of connected then not then connected then not , it must of just upset the modules somewhat and defaulted it to safe , because I have had the battery off before with no adverse effects .


http://i618.photobucket.com/albums/t...psjdsddvtz.jpg
A battery shunt is a device that allows you to go inbetween the heavy cable so you can 'tap off ' and measure amps draw without blowing your multimeter all the time ..... just for those who was wondering don't cha know


Hard work typing all that on an iPhone ....... frekkin predictive text .... a tell thee ..

That's very interesting. Didn't know that the struts were that complex. Cool. Glad it's sorted though. +++

Well done Haydock Lee.
Surprising what comes out of the woodwork of experience.
Really would like you to attend one of our meetings.

Thanks for the detail - makes sense. ECUs scrambled after trying to start the car with a flat battery and bouncing your shunt probably have the same effect.

I never cease to be amazed by the skills ( fault finding and manual) and knowledge of the members of this forum. As someone who is limited in those areas it's a huge comfort that I can call on their experience should something go wrong with my car, rather than be resigned to being ripped off by a stealer or anyone else.

Keep up the great work guys +++

Good investigation there. +++

As to your heights it possible someone has adapted the suspension and offset the figures to fool the ecu into riding lower, but to rectify you need to do the calibration from scratch.

https://www.youtube.com/watch?v=o2aeQ6bhu-Y

Great write up thanks and good information for all - added to sticky +++

Yes , had this in mind ......I do the same on range rover sports and the discovery 3s when the height potentiometers have gone slightly off on the voltage range , just trick the ecm with a different actual reading to get the car balanced .

Thanks for the positive comments , I've been spannering on cars for 30 years now and you do really learn something new everyday , no one knows it all but as a group the knowledge all comes together , I've learnt loads since coming on here , there's some very knowledgeable folk for sure .
I work on everything all models but my favourite field is non intrusive diagnostics so I use a scope quite a lot and use 'in cylinder pressure transducers ' to diagnose say a timing chain stretched or jumped chains or cambelts , don't even take a rocker cover off to diagnose them with the correct tools , it's an interesting field , more enjoyable than fitting discs and pads .... more brain testing .

Ray. going to see if I can get to the owners meet this year , just looking at the pictures of 2015 ,food , beer , car talk , enjoy all that

Now this is an avenue of diagnostics I would like to learn more about, so if your willing to lead I'm willing to follow.

I have a dual channel scope already that i used in the past for simple things, also seen videos for using it to to test for sticking injectors but never had need to put into practise yet but I'm sure theres more that its capable of like you have hinted too.

We have a 4 channel pico , it's a superb scope Im only touching the tip of what's its cable of , there's a great scope forum it's called Auto Nerds .... it's American based so you have put up with , fender , buddy , and muffler a lot but there into it big time .

As for injector testing using an amps clamp with the scope shows you more than the volts and duration wave forms , it shows better how the amps 'push ramp 'is trying to un stick the injector pintle , I'm no expert by any means , you have to use it to learn more .


Going to bore the hell out of you all now , but here's how to tell when you have cambelts jumped or chains stretched or dowel or woodruff keys ' ridden over '



http://i618.photobucket.com/albums/t...pskrqfexj3.png



Blue trace is crank shaft sensor pick up on flywheel , normally around 60 teeth segments less the ' missing tooth ' segments that the ecm uses to reference top dead .

The red trace at the top is the square wave ( Hall effect ) from cam sensor , so you are looking for how many teeth from missing tooth segment to cam sensor switch on time .

The brown / yellow trace is the in cylinder pressure transducer , the peak is max pressure in the cylinder , it all looks a bit confusing dun it hehe !!

Cut to the chase here .....this is a crank pulley that has ridden over woodruff key , no taking engine apart , no cam covers off , all diagnosed from ecm wiring multi plugs and of course having scope traces from a good engine which I can source from auto nerds library or other sources .

You all fell asleep now zzzzzzzz hehe !!

Nope still awake, I'll be sure to check out the nerds

Lee,
This is all good stuff, Luv it.
I have an ex military twin trace scope, not the latest and greatest but still excellent for purpose.
My problems are of age, grey matter is much slower than it used to be, and memory does fail me terribly. My old system of instant recall from the mind pigeon holes fails rather spectacularly. By the time I've recalled what I need I have forgotten why I needed it :mad:
It would be nice if you manage the annual meet. Of course TinTin will be speaking up soon to organise another local gathering.

Ex military scope eh ?? was that the scope you used to decipher the enigma machine it the war Ray ??? :ROFL:

Nah Lee, twas a year or three before then.
I was stationed darn South near Hastings. We were trying to design the optimum arrow trajectory for maximum effect, but the bloodie frenchies beat us to it.

They got our Harold in the eye

Hey Lee,

I had a similar problem in the wife's Q7 - its been a while and is still not gone back to 'normal' - (but she has driven in comfort ever since)

Do you think disconnecting the battery and reconnecting would be the best way to go ? any suggestions ?

i'll try to stay in dynamic ride today as i've got the car for a few days, to see if that makes any difference.
Thx
Bal.

Does the ride height look ok ?? if yes try this .........

Do a hard battery reset ..... remove earth battery lead off battery and cross it over to the positive for 30 seconds or so , this will discharge all capacitors and 'keep alive ' memory functions .

Just taking off a battery lead on modern cars is not a full re boot so that why hard battery reset nessasary nowadays ....... fixes all kinds of issues on Range rovers i can tell you !!

Reconnect battery ....you will have to reset windows and any other learned type functions , put car in dynamic and have a good drive round in it ....vary your speed .... excelerate /de celerate , the ecm should hopefully start to relearn the firmest road map , then try in comfort see if any better .

If this does not fix it i really dont know where to go ???

Would it be possible to "tune" the Suspension computer to send more amps to the struts to be softer?