Citroen C5 X7 very firm suspension

[nomad123]

Hello dear forum members!

My 2010 Citroën C5 X7 with Hydractive suspension has suddenly become very stiff. No errors on Lexia, I’ve checked all 7 spheres with a pressure gauge, they are fine, the car raises/lowers correctly, levels properly, and the pump works.

The body feels hard and behaves unpredictably, on uneven roads it sways left and right and doesn’t float.

Lexia shows yaw, pitch, and roll sportiness always at 100%, even when stationary. Could a faulty yaw sensor under the driver’s seat be causing this, keeping the suspension always stiff?

Testing the middle regulator spheres via Lexia and switching them off doesn’t change stiffness front or rear when pushing on the car with hands.

Thanks in advance for any advice!

[mickthemaverick]

I am pretty ignorant of the X7 I'm afraid but one thought comes to mind, do you have a sport button and if so could it be inadvertantly jammed 'on' ? Just a thought

[Kees]

@mickthemaverick:
Even with the sport stand switch on, the car is in soft mode!!
The difference between soft/stiff is that the threshold for switching is on an other level.

[Kees]

@ nomad123:
Look at my answer on Mick.
The number you see is not an percentage, but it is the threshold for changing from soft to stiff.
Look at the number when you press the sport switch, then you see the number change. This is how the sport stand works.

[nomad123]

Yes, I know how the sport mode works, it’s not a simple on/off button. When I looked at these parameters, the sport button was on, which is why everything was at 100. When I turn the sport button off, the parameters return to normal and vary depending on driving style. So this is not the cause of the hydraulic system’s poor behavior.

What else could be causing the hydraulic system to behave poorly?

[Kees]

Do you have replaced the struts?
There are several post over here, that they replaced the struts from inexpensive struts on the Ebay and get this sort of problems.

[nomad123]

No, I still have the original ones, both front and rear. Nothing has been touched recently. The ride was superb, the car was floating over the road in a controlled manner. Cornering was excellent, with not much body roll.

[Kees]

Well in this case i should disconnect the connector from the stiffness regulator at the back, because if the solenoide is without the 12V then the valve is open and all spheres are connected with each other and must the back side of the car be soft.
You will get a error on the display, but you can ignore this.

[nomad123]

UPDATE: I have fixed the issue. The problem was in the hydraulic pump, specifically in the computer part. The pump itself was working fine, raising and lowering the car normally, but the ECU/BSI section was faulty, which made the ride poor and bumpy, with no proper control of the car. After replacing the pump, the ride is superb again. The strange part is that there were no fault codes, and all the parameters appeared normal when monitoring the Hydractive system in Lexia while driving.

Thank you very much for your assistance.

[Kees]

Good job!!
This means, that the solenoid's from the stiffnes regulator stay under 12 Volt instead of 0V.
So, there is something blown in the ecu.

[nomad123]

Does this mean that when measuring with a multimeter on the connector for the stiffness regulator, it should show 0V if everything is working properly? I measured it with a multimeter and it was around 10–11V.

[Kees]

Yes this is correct as I say before, in the soft mode the connector supply 0V and switch to 12V to go stiff, this is why I gave the advice in my previous post to disconnect the connector at the back stiffness regulator (easy access).
In the past I connect a led on this system to see when the car switch to stiff, because I was not satisfied with the behavior.
Now I drive the car always in the soft mode.
I disconnect the connectors from the stiffness regulator at the front and backside and put a resistor 10 Ohm/10 Watt in place of the stiffness regulator, otherwise you get an error.

[nomad123]

I didn’t understand you right away, but now I measured it with a multimeter and it shows 0V. Well done!
Can we get in touch via WhatsApp, Viber, or Telegram? I’m often working on the car, so we could share our experiences and ideas.

[Kees]

No problem, send you an pb.
Greetings,
Kees.

[Paul-R]

Don't forget to report back here with anything interesting!