C6 Suspension Pump Not Running

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

C6 Suspension Pump Not Running

Post by MGmike »

Ok, there's a bit of a story and I've been a bit gun-ho in my approach to trouble shooting. I've made things worse but I have a plan to get me out of a hole!

the basics are:-
  • New to me 09 C6 with the rear end on the floor.
  • suspension pump not running at all (even as it should when you open/unlock the door before starting the car)
  • Maxi fuse and fuse in glovebox both ok (well, they are now after I blew one!).
  • Pump power relay okay and power to the pump connections
  • This is where I got a bit gun-ho and removed the electronics module on the side of the pump and hardwired 12 to the motor. hay presto the pump runs!
  • What I failed to do was to check how the module is told to switch the motor on!
  • Finally I reverted to Diagbox and get a " no communication with suspension ECU)".
  • I managed to pick up a cheap(ish) C5 pump and used this as a test unit and this comes up in Diagbox as an "unrecognised unit". As this is clearly a different error, it implies the unit has powered up
This leads me to suspect the suspension ECU/BHI as the real culprit but I would like a wiring diagram for the suspension system to work out how the ECU is powered and if possible, how it controls the motor (Marc, can you help please?). I've had a look at the thread on the C5 X7 suspension for which Marc kindly supplied the wiring diagram and I'm fairly sure it's very similar to the C6 but best to check just in case (once bitten and all that!).

Once I confirm power is actually reaching the ECU I need to think about how I can test it further. Is there such a thing as a circuit diagram for the internals or are there any known/common problems I should be on the lookout for? Failing that, is there anyone in the UK who has the knowledge to test and repair it?
Anyone have any other suggestions of things to check?

If I do end up replacing the BHI, I know I'll probably need to do the height programming but does the replacement need coding to the car/BSI etc. I don't think it does but someone has suggested it will do!

Thanks for the support
MGmike

User avatar
KennyW
Donor 2020
Posts: 2104
Joined: 17 Jan 2006, 22:22
x 60

Re: C6 Suspension Pump Not Running

Post by KennyW »

Did you look at my suspension problems on my C5.

viewtopic.php?t=66453

IIRC the C6 has individual height sensors on each corner but apart from that they very similar to C5 x7

What I found out is there is no diagram for the internal electronics of BHI available to us mortals.

I still have a working pump which will fit the C6.

Did you try to swap pump over and put your original suspension ECU on ?

On the C6 forum the problems were related to dirty pump (carbon dust) or faulty module unit (small black box) the one you bypassed.

The suspension ECU's are NOT usually the problem.

Kenny

User avatar
GiveMeABreak
Forum Admin Team
Posts: 23545
Joined: 15 Sep 2015, 19:38
x 2497

Re: C6 Suspension Pump Not Running

Post by GiveMeABreak »

I can't do anything tonight, but will look tomorrow. One thing I can tell you is that the BHIs are different part nos - even with the C6 2.7 and C5 (X7) 2.7 Engines and even where these are not pre-configured.

One thing you have to remember is that on the V6 engines there is a separate suspension ECU (CSS) for both the C5 X7 and the C6. The difference being that the AMVAR active damping function is not utilised / available on the C5 X7 like it is on certain C6s.

The CSS suspension ECU on the C5 X7 V6 models takes the sensor inputs from the 4 corner height sensors and undertakes the calculations, but uses the ECO TECH Suspension ECU incorporated into the BHI for some of the other functions.

The CSS Suspension ECU on the C6 does the same, but also incorporates the active damping for the AMVAR system and sends the adjustment commands to the damping actuators on the special suspension struts that are fitted to these C6 models.

The pumps themselves are only active very occasionally - or they would soon burn out. They only top up the system pressure as needed when being loaded or under load - but most of the time the pressure in the system is adequate for normal operation.

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

Re: C6 Suspension Pump Not Running

Post by MGmike »

GiveMeABreak wrote:
13 Apr 2021, 23:59
I can't do anything tonight, but will look tomorrow. One thing I can tell you is that the BHIs are different part nos - even with the C6 2.7 and C5 (X7) 2.7 Engines and even where these are not pre-configured.

One thing you have to remember is that on the V6 engines there is a separate suspension ECU (CSS) for both the C5 X7 and the C6. The difference being that the AMVAR active damping function is not utilised / available on the C5 X7 like it is on certain C6s.

The CSS suspension ECU on the C5 X7 V6 models takes the sensor inputs from the 4 corner height sensors and undertakes the calculations, but uses the ECO TECH Suspension ECU incorporated into the BHI for some of the other functions.

The CSS Suspension ECU on the C6 does the same, but also incorporates the active damping for the AMVAR system and sends the adjustment commands to the damping actuators on the special suspension struts that are fitted to these C6 models.

The pumps themselves are only active very occasionally - or they would soon burn out. They only top up the system pressure as needed when being loaded or under load - but most of the time the pressure in the system is adequate for normal operation.
Thanks Marc, I wasn't expecting anything last night as it was so late... I'm also not working on the car until the weekend so no hurry.

I'm aware of the AMVAR ECU which should take care of he height corrections. The AMVAR unit is talking to Diagbox thankfully.
I'm also aware the pumps only run occasionally and I'm suspecting the reason the rear is on the floor was a leak from the small rubber hose at the back (common fault on the C6) which had just about drained the LDS. I'll need to get the pump working before moving on to see if there are any other faults to deal with like the digital dash display which isn't working (another common C6 fault!). I'm now starting to wonder if someone has fitted the battery (or jump leads) the wrong way around and taken out these two units, Hmmm. Anyway, one thing at a time...
Last edited by MGmike on 14 Apr 2021, 10:30, edited 2 times in total.

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

Re: C6 Suspension Pump Not Running

Post by MGmike »

KennyW wrote:
13 Apr 2021, 23:46
Did you look at my suspension problems on my C5.

viewtopic.php?t=66453

IIRC the C6 has individual height sensors on each corner but apart from that they very similar to C5 x7

What I found out is there is no diagram for the internal electronics of BHI available to us mortals.

I still have a working pump which will fit the C6.

Did you try to swap pump over and put your original suspension ECU on ?

On the C6 forum the problems were related to dirty pump (carbon dust) or faulty module unit (small black box) the one you bypassed.

The suspension ECU's are NOT usually the problem.

Kenny
Hi Kenny,
thanks for the link, yes I looked through it and think that's where I spotted the X7 diagram.
Yep, C6 has sensors on each corner but as you say, the principle of operation is the same. I suspected there wouldn't be an internal diagram but thanks for confirming. Also, thanks for the offer of your spare. I have one arriving tomorrow that I'll rob a couple of bits off to fix what's here (I hope) but I suspect I might need to use one off one of my spare C6's that I'm trying hard not to break!

I initially thought the small black box was the issue until I connected that part of the C5 pump and the original ECU to see if the C5 pump would run. As it didn't, I then checked with Diagbox to find the no communication issue which leads me to the ECU being at fault. Yep, someone else has told me the ECU's are not usually a problem and it would be just my luck if it is :rofl2:

User avatar
KennyW
Donor 2020
Posts: 2104
Joined: 17 Jan 2006, 22:22
x 60

Re: C6 Suspension Pump Not Running

Post by KennyW »

Worth having a read on the C6 owners forum, quite a few posts re various suspension issues not dissimilar to the C5.

Kenny

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

Re: C6 Suspension Pump Not Running

Post by MGmike »

Thanks Kenny, been over there already and downloaded loads of stuff but the suspension wiring diagram is missing.
I think I have enough from your post to get by this weekend but it would be nice to get the right diagrams.

cheers
Michael

wheeler
Posts: 4796
Joined: 21 Sep 2002, 19:07
x 235

Re: C6 Suspension Pump Not Running

Post by wheeler »

What is your RP number (found at the bottom of the tyre pressure label) & what engine do you have?

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

Re: C6 Suspension Pump Not Running

Post by MGmike »

from memory 10959 2.7 engine

wheeler
Posts: 4796
Joined: 21 Sep 2002, 19:07
x 235

Re: C6 Suspension Pump Not Running

Post by wheeler »

Here you go.
Attachments
C6.jpg

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

Re: C6 Suspension Pump Not Running

Post by MGmike »

Thanks wheeler, very informative and explains a whole load on the AMVAR side of things.
However, I think the bit I need is inside the dashed box 77-- . could you help with that please?
I'm guessing it'll be a lot simpler than the C5 as most of the work is being done by the AMVAR ECU.

Thanks again

wheeler
Posts: 4796
Joined: 21 Sep 2002, 19:07
x 235

Re: C6 Suspension Pump Not Running

Post by wheeler »

OK so not the AMVAR side of things?
Attachments
C6 BHI.jpg

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

Re: C6 Suspension Pump Not Running

Post by MGmike »

Thanks wheeler that's perfect.
Not AMVAR yet. Haven't got that far.... Got no pump running which is a bit of a must have to get started :-D

MGmike
Posts: 22
Joined: 29 Aug 2020, 18:29

Re: C6 Suspension Pump Not Running

Post by MGmike »

Thanks to the wiring diagrams provided by wheeler, todays fault finding confirmed what I suspected :(
Power is getting to the BHI but it ain't doing anything it should be.

So my options are:-
find someone to repair (anyone know of any repairers?)
replace with another second-hand one (I have a spares car but are they coded to the car?)
buy new and have the stealer configure (gulp!)
scrap the car (such a waste of a low mileage very clean car)

All assistance and comments greatly received.

MGmike

wheeler
Posts: 4796
Joined: 21 Sep 2002, 19:07
x 235

Re: C6 Suspension Pump Not Running

Post by wheeler »

The BHI is not coded to the car so you can use second hand ok.
There are some options to configure though, cant specifically remember the C6 but on the C5 its just what type of headlamps it has, what type of steering it has (variable or un variable) and if it has H3 or H3+.
If the donor car is the same spec you may not even need to reconfigure anything.