X7 suspension woes

[Bandit12]

While my X7 was jacked up to top up the diesel additive I thought I would replace the rear height sensor as it failed some time ago causing the rear of the car to sag a an inch or so.
I replaced the sensor and the car is now undrivable- bouncing up and down picking up every bump in the road. Its like being strapped to a road drill!
The rear also no longer moves up and down inline with the front. Diagbox lists no obvious fault codes but after 3 hours struggling with this I am not convinced I was successful and have given up for the time being
LDS level looks ok and pump appears to work fine. I did notice the clamp for the sensor "dog bone" was a little loose so I tightened it up and the clamp may have moved a fraction. Is the system that sensitve? Is there a starting point with the clamp that I can measure against to see if this is the problem?

Any advice is appreciated

Bandit

[GiveMeABreak]

The clamp should never be adjusted normally as the slightest movement can make a big difference Gino, - so yes to your question - it is that sensitive. The clamp is only used initially when setting the vehicle heights at factory. Diagbox is only used for fine tuning the heights within a small range of movement.

If the clamp has to be moved for whatever reason, its position should always be clearly marked beforehand, so it can be replaced in the identical position. There is no positional data for the clamp that I have - only on height measuring for the fine tuning of the vehicle using Diagbox. So I can't help you with this - but if you can get it to a dealer they may have something or be able to set it up correctly - they will probably be able to find out the info from France if they don't have it locally.

The picture below may help as a very rough guide as to its position - but of course won't be accurate.

Procedure for removal and refitting for future reference:

Disconnect the connector (at "h").
Uncouple the rod (15) from the lever (14).

Remove:

• The (13) bolt
• The beam height rear sensor (16)

Refitting

Refit:

• The beam height rear sensor (16)
• The (1) bolt, tighten to 0,4 ± 0,1 daN.m

Couple the rod (15) on the lever (14).
Connect the connector (at "h").
Return the vehicle to its wheels.

[Bandit12]

Thanks Marc. Your pics and explanation are very helpful. I'll book it into the dealers but while waiting I'll keep fiddling. I did have a thought. The sensor works on linear resistance, with a minimum and maximum. I presume therefore the median would also be a good starting point to set the sensor arm to. I've the old senor on the bench and can check resistance with the arm in different positions to find that median then mirror the angle on the new one. Or is this just wishful thinking-chuckle

[Bandit12]

Just been tweaking it for the last hour and getting very close to "normal" citroen behaviour. Still not right though cos I can get it to look level in the normal position, then I lower on the button and all still looks good but when I try and raise it up the front moves but the back stays at the lowest setting. I little tweak of the sensor clamp and the cycle repeats. Either it stays up at the back or it stays down. In another time and place this might be funny but I'm supposed to be taking family to heathrow on sunday!

[GiveMeABreak]

Thanks Marc. Your pics and explanation are very helpful. I'll book it into the dealers but while waiting I'll keep fiddling. I did have a thought. The sensor works on linear resistance, with a minimum and maximum. I presume therefore the median would also be a good starting point to set the sensor arm to. I've the old senor on the bench and can check resistance with the arm in different positions to find that median then mirror the angle on the new one. Or is this just wishful thinking-chuckle

On the 4 Cylinder X7, the only data I have on the height sensor is the following:

"A" is the output voltage of the Body Height Sensor
"B" is the angle of the Body Height Sensor.

A negative value of the angle of the body height sensor corresponds to compression of the suspension.
A positive value of the angle of the body height sensor corresponds to release of the suspension.

So I'm not sure how this if going to help you any as the sensor will always connect up to the same position that the clamp is fixed at when the 'dog bone' is attached, so there is nothing to change in the sensor itself - as that only changes when the rear rises or lowers of course.

Your issue is with the clamp, not the sensor, so you'll need to reattach the sensor and dog bone and finely adjust the clamp by millimetres at a time until Diagbox shows the height settings as close to the height reference values as possible. That's my only suggestion outside of getting the dealer to do it.

The issue is ensuring it is at the correct height to start with though - and that is your problem if the vehicle is not sat right as it is. At least in the dealers they can do the height measurements and get the vehicle on a 4 post lift and lower the car down to the correct height gradually when the wheels make contact with the ground - gradually lowering it with the lift until they get it at the correct height, tighten up the clamp and then check the fine tuning with Diagbox.

Of course usual safety warning about not getting under the car when doing this without the vehicle being independently supported - as changing the clamp position can cause the suspension to drop instantly - as the height correction will operate without the engine running.

[Bandit12]

Thanks for the graph Marc, I agree dealers should be able to fix this if I can't. I'll book car in tomorrow but I expect there will be at least a week wait which will give me time to continue to fiddle and fine tune

Gino

[white exec]

Guess it's important not to set the adjustment collar to a position where body movement could force the sensor to/beyond its mechanical limits.
Guess again that setting up would involve putting car at its correct normal running height, then adjusting so that sensor gives a specified output voltage, or resistance point.
As you say, dealer workshop should know.

[Bandit12]

I spent an unsuccessful couple of hours fiddling with it this afternoon. I can get it to within a millimeter or 2 of where it should be but each time it looks right, the back end sinks to its lowest setting and I have to start again! Its booked in for tuesday at the dealers. £114 just to hook it up to a computer!

[Bandit12]

Dropped car off at dealers this morning and just received a phone call. ITS BAD!!!!!
They said the following
"There's no communication with the suspension ECU. Theres no communication with the power steering ECU, Theres no communication with the headlamp adjustment ECU and at this stage they have no idea why."
They ask authorisation for 4-6 hours at £100 per hour for further diagnostics including removal of bumpers and lots of wire tracing. This could cost 800-900 quid just to find out what the problem is!
My questions are
how much for a new suspension ECU/power steering ECU/headlamp ECU?
Can second hand parts be fitted and/or do they need programming etc?
Anyone undertaken these jobs successfully?
I'm working out worst case scenario as car is 11 years old with 125000 on the clock.

Do I fix or do I scrap and replace?

Any advice is really appreciated

[Paul-R]

How much has the dealer visit cost you already? In fact how much have you spent in total so far?

[Bandit12]

£114 for the diagnostic. Ive just MOT'd serviced car replaced a tyre and topped up additive tank.
Just been online and to replace the car with like for like is minimum £2000

Gino

[Paul-R]

Oh dear, between a rock and a hard place.

I remember when the dog-leg fell off the rear on my Mk1 C5. When I first replaced it I managed to put it on wrongly so that the link arm pointed up rather than down (or back to front - something like that) and this confused the hell out of the system! When I corrected this I ended up setting the height simply by rotating the clamp on the anti-roll bar until the car looked right and the wheel arch looked correct around the tyre. A bit of fiddling got this correct enough so that I didn't get flashed by oncoming drivers at night. So take a very close look at how you've assembled it as the anomalous behaviour when you lower and then raise the suspension might point towards this.

It seems strange that so many other faults suddenly developed as a result, perhaps they were always there but haven't affected normal functioning. Have you noticed a problem with the power steering, headlamps (I presume you have the Xenon type) and suspension other than the known issue? The ECUs may be faulty but first I would be taking apart and remaking wiring connections all over the place in case there's a bit of corrosion somewhere. Especially the connection to the rear sensor. Also the wires themselves there in case there's abrasion to the loom.

[Bandit12]

Hi Paul
. Back end dropped a bit over a year ago so I moved the rear clamp on the torque bar by a couple of mm to get it to raise the back up which it did. headlamps have been pointing low for some months, (probably as a result)
no issues with steering or anything else I noticed.
However when putting car on diagbox a week ago I saw this error which is exactly what dealers told me this morning.

[Paul-R]

Hmm, I was going to say that I wonder whether you need a later version of Diagbox than 7.02 (Marc, can you chip in?) but the fact that the dealer says the same sort of puts the kibosh on that line of thought.

I think I'd still try unplugging and remaking connection on things, especially those ECUs. Wherever they are situated! I'd also use some contact cleaner on the exposed connectors while they're apart. I have a tin of Super Servisol I've had for years. There are two types, cleaner only and switch cleaning lubricant. I use the latter.

[Bandit12]

Thanks for your tips Paul, most appreciated . Regarding diagbox, I'm using a very old and painfully slow laptop that makes using diagbox a real pain . I've just been given a newer one which I have reformated and installed XP. I've tried a couple of times to install diagbox but it does not run but I will keep trying.

Regarding the car, the dealer estimated they needed 4-5 hours to take bumper off and strip car to check wiring and find out whats going on so I authorised them to do so. My view is the car is sound, its gone through every MOT with flying colours no advisories (apart from worn tyre). I like the car and plan to keep it for the next 5 years and it will cost me 3K+ to replace it with like for like.
I'm hoping dealer will be able to tell me exactly what the problem is but dreadling being told they don't know and can't figure it out and its all beyond them.
I do know that having a good version of diagbox is essential for me so while the cars in the workshop I'll focus on that. However this works out i do love citroens and plan on owning one for years to come.

Gino