2007 Citroen C5 2.2 Front suspension issue

[ryanc5]

Hi I've been on the forum a while but havent posted.


I have a 2007 C5 2.2 hdi vtx+

I bought the car with a suspension fault and am yet to cure it. It was regularly popping the maxi fuse and dropping down, so I replaced the pump/motor unit with a known good second hand one hoping this would cure the problem. It did and after a week the fuse still hasn't popped

Issue is the front suspension will at best be at half the height it should and will constantly hunt up and down and be very firm. If the car is switched off it will drop quite quickly and come up slowly. The rear seems fine and in the mornings it will still be up. I have a friend at Citroen that advised me on the bleeding procedure which I followed and also to try to bleed the front stiffness sphere which I have done. There are no visables leaks anywhere on the car.

My thoughts are the maxi was blowing because the worn pump motor was working to hard because of the front end issue but I cant get to the bottom of it. I dont have Lexia but the diagnostic I do have access to only brings up a fault for steering angle sensor. No warning lights on dash at any time.

Had a good search on the forum before posting

Thanks
Ryan

[GiveMeABreak]

When you replaced the BHI, did you replace it with the exact correct part for your vehicle - these are all different depending on model, engine and build and H3 system you have.

The bleeding process is simple to do on these and required nothing more than lowering suspension, removing LDS cap and very slowly turning the steering wheel lock to lock 5-8 times, checking LDS for fizz, topping up to the levels and repeating if you still have air bubbles - there is nothing needed to be done on the spheres! On H3+ systems, the valve on the front block is for manual depressurising only (where you don't have a Lexia) - not bleeding.

Probably also best to pop your VIN up so the staff know exactly what system you have.

[ryanc5]

My vin is VF7**************[VIN obfuscated, can be read by forum staff]


As for the BHI? Take it thats french car forum slang for the pump/motor unit? I just took a unit that looked identical to mine. Have no idea of the details of the car it came out of to be honest.

[GiveMeABreak]

That's likely to be a problem then....

The BHI (Built-in Hydro-electronic Interface) is a combination of the suspension ECU, the hydraulic block and the pump motor. These are matched to the specific vehicle's options. Apart from the different types of suspension (H3 and H3+) which have different setups, additional spheres and hydraulics, there are the different parameters programmed into the units specific to the suspension type, saloon, estate, auto box, manual, engine etc. so you may find that the unit is not compatible.

The correct Citroen part number for reference is: 5277C9

Some other points: Your C5 has a Steering Wheel Angle Sensor - this is used with the ESP system to determine the angle and rate of turn. It has to be calibrated using a diagnostic (Lexia) if the ABS / ESP ECU is changed - but possibly also if the BHI is changed. The SWAS is also used to inform the suspension ECU so it can determine whether to engage and if so, for how long, the firmness (sport mode) is active.

There was always some 'hunting' on the early C5s - the car would often nod when parked or after a drive as the system adjusts itself, but this was random.

As for the height issues and the previous issues aside, you may also have a height corrector problem. Either the joints are stuck or the height corrector itself is end of life. The potentiometer tracks may be work or have suffered damage from the elements over time. When this happens, the analogue data is sends can be incorrect, causing the suspension ECU to try and correct for a presumed height imbalance. Of course this can then cause the pump to overwork and overheat, blowing a fuse. It is not supposed to operate constantly - only occasionally as needed to maintain pressure unlike the older systems that has a pump constantly running.

So there's a few possibilities to consider - but whatever you do, if checking the height correctors - DON'T get under the car without axle stands or another support being in place - as these can and have in the past suddenly collapse and crush you. Also, don't undo the clamps of the height corrector on the axles without marking the position (you shouldn't need to touch this though)- otherwise the heights will be stuffed more than they are and you will need to get them reset and measured. Also the height corrector should be pegged before removing it, so that the new one can go back in the correct position.

[ryanc5]

Appreciate the detailed reply. These really are specialised beasts.


Is the part number you listed, the BHI part number I should be running in my car? I will check this today. I still have the old unit so possibly I could reuse it with the new motor?

As for the steering angle sensor. Will this only cause issues with Sport mode or even in Normal driving setting?

I've checked the front height corrector and it's not seized and on the actual sensor itself there looks like "breakers" markings on it which suggests to me it's been changed but no guarantees its I'm good order. Would a faulty sensor bring up any codes?

The car in the past week has actually got maybe 25% better in that it doesnt feel like its constantly changing the ride height while driving and is now keeping height at the back I'm the mornings but still down at the front. Definitely some improvement.

[ryanc5]

Should add, I've came to the car this morning and it was down at the rear and up at the front (as much it gets for this car) as soon as I started it, up it went at the rear.. took it for a drive and it felt like it was rising at the back too much and still firm at the front. Its hard to know how many of these problems where present with the old BHI or of the new one is causing more issues than it cured.

[GiveMeABreak]

If you have a problem with the steering wheel angle sensor, then it will throw an ABS / ESP warning up as without the SWAS, the ESP system cannot operate.

If you have your old BHI, there should be a label on them with a load of numbers, possibly starting 96 or 98 - if you have that it will be useful and you can compare with the number on the one you have fitted.

[ryanc5]

Just to update, been busy but got another go at this headache.

Adjusted the height sensor on the front anti roll bar and the car raised immediately and while running will sit at a better height but still hunt. Once switched off it will gradually drop all the way down at the front. The rear stays up as it should at all times and is comfortably over bumps whereas the front is hard.

My thoughts on this are with the change of BHI I've the same issue with the front end except no blowing of the maxi fuse. I haven't had a chance to get the numbers off both BHI.

[ryanc5]

These are the fault codes I currently have today

U1108 No communication with engine

U1118 no communication with bsi

U1205 no communication with Steering angle sensor
Incorrectly received