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Adjusting C6 suspension height

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cruiserphil   
Sun Jan 15 2012, 07:37pm

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Lads,

I finally sorted out the failed programming of front right hand height sensor but it took about a day plus a lot of head scratching and trial and error. However, what I found I think will be of interest to those of you who try this out as just following the step by step instrucions in Lexia may not be enough. You may need to do some corrective maths.

First follow the measurement instructions in the mainenance instruction (available in C6 owners). Effectively, you measure each actual wheel radius (including tyre) Rx and the height of the respective vehicle measuring points, HxM on the front and rear subframes. The target is to get the each wheel height KxM = Rx-HxM to be 160+/-6mm for the front and 111+/-6mm for the rear. So for example my front LH wheel radius R1 is 310 mm, so to get K1M = 160 mm I needed to measure H1M = 150mm. The rear RH wheel radius R4 is 320mm, so to get K4M = 111mm I needed to measure H4M = 209 mm.

When I changed the wishbones, the maintenance instruction advised to reprogramme the vehicle heights. So I hooked up Lexia. To set vehicle height you go -> DIAGNOSIS -> GLOBAL TEST -> VARIABLE DAMPING -> SPECIFIC AFTER SALES OPERATIONS. Basically the procedure is that it asks you to enter each of your Rx and assocated Hx measurements as you find them. This I did and the actual measurements were: R1 (front LH) = 310mm / H1M =124mm, R2 (Front RH) = 310mm / H2M = 126mm, R3 (rear LH) = 318mm / H3M = 207mm and R4 (rear RH) =320mm and H4M = 210mm. So , the rear was in spec. but the front was nominally 25mm too low. So I thought that, once programmed, the car would know where actually it was and then with its sensors make the calculation and correct the car height. No!

It continually threw up "programming failed" and said check sensors, wiring etc. By going VARIABLE DAMPING -> PARAMETER MEASUREMENTS -> STANDARD PARAMETERS - > PROGRAMMING STATUSES it displayed that front RH sensor programming was INCORRECT. Countless repeat inputs failed. I decided to replace the RH sensor. In the interim the car's front suspension became stiffer - I think this is a default mode in the case of an incorrectly programmed or defective sensor.

I replaced the RH sensor but effectively no change. The breakthrough was going VARIABLE DAMPING -> PARAMETER MEASUREMENTS - > STANDARD PARAMETER MEASUREMENTS -> HEIGHT CORRECTIONS. I show the screen as it shows with everything sorted:



However, for front right hand movement, the figure was showing about - 20mm. This means that the system was saying that the front right hand was 20mm higher than the reference height. But if anything, it was 20mm lower. I decided to correct for this by adding 20mm to my H2M reading making it 146mm. Repeated the progamming and voila - "programming done." I took the car for a spin and the suspension was lovely again. However, the front was still 20mm lower. So cheekily I decided to tell the car that it was 20mm lower than it actually was. So H1M became 104mm and H2M became 106mm. Programme again - programming done and voila - cars raises 20mm.

So I fine tuned again and this brings me to what I find is what you need to do:

Measure your wheel radii R1 - R4.

Measure your heights H1M - H4M.

Work out the K1M - K4M. If a KxM is greater than the spec. subtract the difference fom your HxM. If a KxM is less than the spec. add the difference to your HxM.

Look at the screen above.

Check the movement for each sensor. If the value is positive it is saying that that the height is below the reference height by that amount. So subtract that height also from the relevant HxM. If the value is negative it is saying that the height is above the reference height by that amount. So add that height also to the relevant HxM.

Programme again.

It will ask you to reenter the figures after getting you to force height correction at each end of the car by pressing down in turn. For these figures, enter the actual values for HxM you measure again at this point.

So at the finish I ended up with K1M = 160mm, K2M = 162mm, K3M = 106mm and K4M = 106mm.

Took the car for a spin and suspension lovely.

Notice too that in the screenshot all the widely -ve and +ve height corrections have disappeared.

I hope this is of help and I needed to write it down before I forgot what I had done. At one point I feared I had a faulty suspension ECU.

Finally, anyone in need of a second hand RH front height sensor?

Regards,

Phil C.
11 User said Thank You to cruiserphil for this Post :
 Gobxoy (30 May 2012) , gmerry (31 May 2012) , Chevrons (16 August 2012) , drummond (17 August 2012) , dinozaurul (14 January 2014) , mtee (15 February 2015) , eduardomaio (01 August 2015) , davidlaver (14 January 2016) , ul9601 (19 July 2017) , Nikola (17 April 2019) , Candide (26 May 2019)
Chevrons   
Sun Jan 15 2012, 08:26pm
Joined: Apr 10 2010
Member No: #85
Location: N. Staffs
Phil,

Errrrr, thanks for that; have to admit I read it.

cruiserphil   
Sun Jan 15 2012, 08:34pm

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Chevrons,

Thanks. I know it's a bit heavy for a Sunday night.

Phil C.
gmerry   
Sun Jan 15 2012, 10:34pm
Joined: Dec 11 2009
Member No: #21
Location: Scotland
Brillant post. Lexia is often not that straightforward. I bet dealers get this wrong if they are not often working on C6s.

Regards
G
cruiserphil   
Mon Jan 16 2012, 09:46am

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Thanks G.

Certainly took a while to figure out. Will be interested to see how it works for others. I'm going to check out the other car next weekend.

Regards,

Phil C.
michaelb   
Mon Jan 16 2012, 10:21am
Joined: Nov 17 2009
Member No: #14
Location: London
Phil, that's amazing. I didn't know one had to be Professor Brian Cox to run a C6. I doff my cap to you sir.

I'm going to be in Baile Átha Cliath in May for my nephew's 21st, can I book a service slot with you and your Lexia around then? I can pay in Sterling Euros or LDS fluid
cruiserphil   
Mon Jan 16 2012, 11:59am

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Thanks Michael B.

You're more than welcome. Send me a PM closer to the time of your visit and see if we can meet up. Our house is only about 40 minutes out the M4 from Dublin city.

Regards,

Phil C.
robin-hood   
Mon Jan 16 2012, 11:24pm
Joined: Feb 11 2011
Member No: #377
I had the same problem. First it was actually a height sensor that was faulty. I changed it and adjusted height via lexia.

next time I found that my first height setting was not perfect (I didn't reinput the actual height for confirmation, but the first values so it adjusted again, too much) I tried to make another setting, and this time, impossible.

It was saying adjustement failed, try to change/verify etc...So I bought a sensor for the wheel I thought it was coming from, and nothing changed. It was not the right color ! So I bought the right one, but again it was not fine.

The problem was very vicious. You must adjust on a very plane area with not big differences in wheel movement ! I tried again on a flat garage, perfect. I put 5mm+ on height according to manual, because my road are very poor and I need more compression clearance than rebound. 5mm more (or less) is the limit. (K1M/K2M at 165 mm and K3/K4M at 111mm). Nothing very huge but when hurting a pothole, 5mm more iin travel can change everything !

cruiserphil   
Wed Jan 18 2012, 12:26pm

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Robin Hood.

Interesting to see that I wasn't the only one having problems in setting the heights. Sometimes when things get complicated you fear that you are overlooking something simple.

Regards,

Phil C.
gmerry   
Thu Jan 19 2012, 08:04am
Joined: Dec 11 2009
Member No: #21
Location: Scotland
Phil, you have done us all a great favour with your write-ups.

I consider myself reasonably competent with any spannering required on the front suspension and with your help, think I could tackle any height/suspension computer setup work required as a consequence. My only problem would be finding a properly flat reference surface from which to measure the height settings.

With regard to entrusting the work to a dealer, I'm afraid I would have my reservations as to how well they would do this work (this is apart from any cost considerations).

Regards
G

PS, I've seen the rear wishbone bush or sale (at least on ebay) as a separate item to the main wishbone.
robin-hood   
Thu Jan 19 2012, 09:33pm
Joined: Feb 11 2011
Member No: #377
The suspension height setting was not properly done on mine when I bought it ( too low at the rear).

As the main operator is a human, from its ability to measure very precisely the distances from frame to floor depends the final height setting precision.

I can see some C6 in my city that had not a good height setting, probably after an operation on suspension parts height measurement was not properly operated.
drummond   
Fri Jan 20 2012, 07:56am
Joined: Sep 20 2010
Member No: #238
Location: Aldeburgh
The DS Pallas had a thick pile carpet on the floor, and the height setting with the suspension at normal is (something like) 231.7mm between the ground and the carpet.

I particularly like the .7!

I have a tool (piece of metal which is U shaped) which is the right height, for the normal cars, (i e non Pallas). I made it, because I could not see my being that precise with the tape measure. Seems like something similar might be useful with the C6.

Tim
1 User said Thank You to drummond for this Post :
 dinozaurul (14 January 2014)
Gobxoy   
Wed May 30 2012, 05:00pm
Joined: Jan 20 2012
Member No: #786
Location: Essex
cruiserphil

What an excellent post.


1 User said Thank You to Gobxoy for this Post :
 cruiserphil (30 May 2012)
feef   
Sat Aug 01 2015, 10:23am
Joined: Apr 12 2013
Member No: #1260
Location: St Neots
For the second height measurement, did you do that with the load still on the front/rear to force correction, or did you lead the front/rear, allow it to correct, then unload and then measure?

I'm getting as far as the first "programming done" but failing on the second verification, and often when I restart the process I get several "programming failed" before hitting upon a "programming done" again
datmbn   
Tue Sep 22 2015, 09:23am
Joined: Jul 29 2010
Member No: #193
Location: MOTALA
I was just adjusting my car and find it strait forward but it was an 2.2 with no variabel damping.
Then i reed the instruktions for both with and witout variabel damping and realised that one part in the instruktions for the non variabel was left out in the instruktions for the variabel damping (maybe an copy and paste problem)

It says:
Calculate : 320-(R1-H1M)(for the front)
Re-enter this value in the diagnostic tool
Calculate: 222-(R2-H2M)(for the rear)
Re-enter this value in the diagnostic tool

Regards mats
2 User said Thank You to datmbn for this Post :
 321dave (22 September 2015) , cruiserphil (22 September 2015)
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