Adaptive Suspension Problem

[F15er]

Hi folks, my F15 developed a problem that driving me up the wall currently.

It has the adaptive shocks and it used to drive like a rolls royce.

I am not sure what went wrong but car is now bouncy and suspension is so harsh and that's in comfort, sport mode is unbearable.

It has the 3rd row seating so has airbags at the back.

I calibrated ride height, and gone through all the suspension related service functions but not made any difference.

Replaced all accelerometers on the shocks and it has a new set of shocks at the back.

Its been to an independent bmw specialist, they tried upgrading the software in the car but no change. They are saying hard to go after anything without any codes.

Has any of you by any chance came across this issue.

many thanks

[lht5059]

Have you checked if your rear airbags are leaking? Mine was leaking and the car drove pretty bouncy, but swapping them out for new bags fixed it.

[RED_Y_]

Yep second that, check the airbags for leaks.

[F15er]

Hi guys thank you for the replies, no they are not leaking. I was sad enough to measure the distance between the top of the tyre and wheel arch to see if it even sags little bit.

[cfm56d7b]

Did this problem develop over a longer time period or appeared suddenly?

[F15er]

Originally Posted by cfm56d7b

Did this problem develop over a longer time period or appeared suddenly?

Appeared suddenly, just before Christmas.

[cfm56d7b]

Originally Posted by F15er

Appeared suddenly, just before Christmas.

If the problem appeared suddenly, then it's a component failure. Which one is of course a $64K question.

Does the suspension feel "crashy" or overly stiff as if only one adaptive setting is active?

[F15er]

Originally Posted by cfm56d7b

If the problem appeared suddenly, then it's a component failure. Which one is of course a $64K question.

Does the suspension feel "crashy" or overly stiff as if only one adaptive setting is active?

Well its odd to describe, it is crashy if you hit a pot hole. However on motorway it still very stiff almost feels ridged.

If you trash it on a really bumpy road it starts to absorb little bit but at steady speeds suspension wont respond quick enough i believe it doesn't open the valves on the shocks hence the stiffness.

Now BMW TIS is on about having 3 different fail safe maps but I have got no codes anywhere.

When i check vdc under control tree the accelerometer voltage fluctuates 0.1v for example it will go from 5.0 to 5.1v and the sensors need 5v supply but dont think that has anything to do with it. I ordered a second hand VDC unit to see if that's going to make any difference but i am well out of my depth now i think. However other than changing front shocks, wiring harness and vdc module all the system components been changed. Unless ICM is asking VDC to stiffen the shocks as it relies on other sensors to calculate the stiffness of shocks.

Below is the fail safe explanation.

Fail safe
Depending on the type of fault that has occurred, the fail safe takes effect in 3 stages:

Stage 1: substitute values

If for example the signal from the lateral acceleration sensor is not available, other parameters are used as substitute values for the identification of cornering. The driver does not receive a Check Control message: no fault entry (only a slight loss of comfort is perceptible). Any repair required is performed by fault entries from the transmitter control unit.

Stage 2: constant voltage supply

The EDC control unit specifies a constant damping force for all 4 wheels (medium-hard damping). A faulty vertical acceleration sensor (not M GmbH) can, for example, be the causal factor here. A Check Control message is output to the driver. A fault is entered in the fault memory (forced activation of DSC).

Stage 3: No current supply under the following conditions:

If there is undervoltage on the load line (failure of fuse)
If there are faults on the lines to the EDC valves (short circuit to B+, short circuit to ground, line disconnection)
:

The EDC control unit no longer energises the EDC valves. This causes the valve to move to a position that corresponds more to medium to harder damping. A Check Control message is output to the driver. A fault is entered in the fault memory (forced activation of DSC).

[F15er]

UPDATE: This is potentially fixed, culprit is ICM (integrated Chassis Management)

For whatever reason it was corrupted, reflashing it seem to fix the issue just need to test it further.

I would like to thank CnSky for his help, once again forums proven how much of a knowledge resource they can be. If it wasnt to his post I would of sold the car as I was fed up of it.

After agonising 2 months and a lot of money for diagnostics and the problem was just the a control module needs reflashing.

None of the specialist or dealers understand or fix it.

Hope this helps someone else.

[Proffo]

Hi,
I suspect I have exactly the same problem which has been driving me crazy for over 12 months. A quick check via ista and the system only seems to be communicating with the front 2 dampers.
There are no codes whatsoever but there are no values for the rear dampers. It’s almost like the system is not recognising they exist and is not looking for them.

How do I reflash the module?