Recently changed front left damper for Miessler unit back in February after purchase. Still sagging a little overnight, and after a cold spell found front right damper was hissing. Warm weather allowed me to hold off for a bit but it finally blew the other week so I fitted a new Miessler unit, same as on left side.

Overnight sagging remains! Still lowers nose first. But here's the weirdness. Since fitting new unit, damping seems firm for the first 10 minutes or so driving and then they return to normal. No errors on dash, no DTC's logged.

Car was very high after fitment of new damper, 400mm at the back, so I ran a calibration on my iCarsoft V3.0, which always fails at the end (I put that down to I need to trick it into thinking it's calibrating a 2006-2007 as it won't do 2002-2005) but it does calibrate and indeed leave the car within correct height tolerances.

No fix! So today I went into suspension live data and saw that it was giving me a "Damper Firm - Error" NO when parked and then YES as soon as I start to drive. After a short 10 minute drive it switches to NO and the dampers run soft again. I have checked for leaks at the valve block and saw a small bubble appear when manipulating the lines (not constant bubbling) at the line that goes into the tank. Gave it a small tighten and it seems to have stopped the leak. Will see in the morning... All other sensors are giving proper feedback. "Damper Firm - Low Vehicle Velocity" YES when parked and switches to NO as soon as on the move. Again, no DTC's are coming up, no air compressor error on dash at any time...

Only thing I have left to try is to fit the compressor refresh kit I bought a while ago as I'm thinking that maybe the compressor which has suffered excessive wear for sure, is probably taking a little too long to do it's thing which is what might be causing the dampers to detect a fault and stay firm.

Also, if there was a leak at the rear shocks, would the fronts dip first? If I leave it for a few days, nose bottoms out first and then the rear follows.

Any thoughts/experience?

 

I have the damper firm error also. No DTCs. Shocks pump up and hold air /level. Very strange error. I just ordered SDD software cus my I 930 just does not show anything else. I am at a loss. Mine is 2008.

 

Have you had any work done recently?

 

No work done recently

 

Looks like this one has got everyone stumped!!

Mine stops giving an error after 10 minutes and dampers run normally after that and pretty much all day…. I’m going to refresh the compresor, see if that helps any.

 

Aren't the damper firm and ride heights totally different systems?
Wouldn't the damper firm be related to the shock's internal rebound setting which is controlled by the CATS system via the small two pin connector going into the top of each strut assembly?
Whereas ride height and suspension leakage is the air management system adjusting and maintaining the correct air pressure to each suspension strut and has nothing to do with shock absorption and rebound rates.

Do you have a calibration error with the new strut that has been installed not physically matching the settings of the remaining struts?
Perhaps is was set to hard when installed to a system that expected the valve to be in soft end of adjustment at the time........
There probably is a procedure for re-calibrating CATS to see if you can bring it back into expected range....but I am only guessing.
Perhaps another member can shed some further light on this.

 

That's an interesting point. I am suspecting that I might need to exchange the new damper... I have tried contact cleaner down the plug hole but no fix. Something I also noticed on my live data is that the rear right height readings are off in comparison to the left side. I noticed that when calibrating, the right would consistently settle 5mm below the right side which it has never done before. It's always calibrated to within a mil either side... Makes me wonder if the CATS interprets this as "odd" data, as if the car was in a corner, and takes a few minutes to figure out that it isn't getting coroborative data from speed, steering angle etc.... I'm going to go for a battery disconnect. See if that "resets" things.

 

Quick update. Reset doing the negative terminal battery trick and leaving it all disconnected for 15 mins. Still errored but on the way to the shop to calibrate, I noticed live data reads constant +6-10mm difference between left and right rear. Right reading a higher number constantly. When the error disappears, the difference between both sides behaves more normally. Did a calibration, this time got a CORRECTLY CALIBRATED message!! So it seems all it needed was a reset. At least that's something positive... Difference in physical height remains around 7mm lower on the right after calibration but the sensors are showing similar heights between sides. Again, it's not showed a firmness error as it need to sit for a while to do so. Now just waiting to see how it behaves after a long stop...

I'm also thinking these Miessler units don't hold air very well. Can't find any leaks in the system so I'm wondering if overnight drop is a "thing" with these units... At least they have CATS (how's that for irony!).

 

Reviewed the schematic to try and better understand the systems and how these components might interact.
The damper actuators are driven directly out of the air suspension control system as a PWM (Pulse Width Modulation) voltage that is sent to the actuators to modulate them as to how far to open (just like the throttle body motor).
So being a PWM driven actuator, they likely have a spring return inbuilt the actuator so when they are not being driven with a PWM signal, they likely automatically spring return the actuator valve to a "zero" resting state.
If that is the case then as you plug in the actuators they should automatically open the valve to the amount as being commanded by the PWM drive voltage.

There is no electronic feedback from within the actuators to give any positional information back to the air suspension controller, therefore it is just sending a series of fixed values of PWM signal that instructs the valve to open a prescribed amount according to the vehicle's speed, driving mode selection (normal or sports mode) and other inputs such as accelerometers (front and rear), perhaps also the yaw sensor.

As mentioned in other threads, the suspension moves into firmer damper operation when the vehicle is moving at lower speeds and then softens the dampers once road speed moves above perhaps 25kph.
That is what you are seeing when you see damper firm - low vehicle velocity in your reader, no fault present, just normal pre-configured suspension behavior.

The question is why do you get damper firm errors when you first drive the car if you are exceeding the low vehicle velocity threshold and why for just the first 10 minutes?
I assume you are not having speedo issues, ABS or DSC messages within that initial 10 minute window that might point to any wheel or transmission speed sensing or processing errors.
Is your reader able to discern front from rear, or just reporting overall?
Aside from that, can you feel during your driving if it feels like it is just the front dampers that are behaving firm, or is it front and rear?
Is the answer possibly that the new Miessler units "damping" capability is more prominent than the original dampers and the air system is getting feedback from the accelerometers that is falling outside what the air system controller expects to see until those shocks warm up and their behavior perhaps changes slightly.
What else might give that 10 minute time delay before the dampers release.....I doubt any engine or transmission temperature feedback would factor into air suspension equations.

If it were air pressure the controller would understand if the air shocks were over inflated and thus appearing to ride harder, as the height sensors feedback would be telling it that the ride height was above expected readings and the ride would naturally appear stiffer.

I don't know if there is still possibly a damper actuator calibration that may be able to bring the air system configuration to understand and accept the new component responsiveness to a certain degree.

 

Thanks Mark, that's very informative. I still haven't moved the car so don't know if yesterdays calibration has changed the behaviour. I installed the same Miessler unit on the left side back in feb, no problems. Everything has gotten weird from the second unit, right side front, install a few weeks back.

So yes, I can see a lot of information, front and back and individual shock firmness side to side, voltages, etc on live data and everything seems to operate normally. As you mention, when I start moving I see the low vehicle velocity change from YES to NO as it should. The firmness error is NO when stationary and as soon as I pull away, not reaching 25kph, probably only about 5kph, I get the YES error...

Very noticeable in the rear, feels like it might ONLY be in the rear.

 

This is all the live data I'm getting parked up after a 10 minute drive. The system sorted itself out after only 4 minutes (timed) and started running normally:

Acceleration sensors supply : 4.68V
Damper firm - Battery voltage out of range : NO
Damper firm - Error : NO
Damper firm - Lateral acceleration : NO
Damper firm - Longitudinal acceleration : NO
Damper Firm - Long wave : NO
Damper firm - Low vehicle velocity : YES
Damper front firm and rear soft : NO
Front left damper status : 15
Front right damper status : 15
Damper front soft and rear firm : NO
Damper left firm and right soft : NO
Damper left soft and right firm : NO
Rear left damper status : 15
Rear right damper status : 15
Front vertical acceleration : 0.1g
Bear vertical acceleration : 0.1g
Brake fluid hydraulic pressure : 0 bar
Control module status : Operat.
Number of permanent diagnostic trouble codes : 0
Steering wheel angle : -4,15
Calculated external temperature : 33.5 ºC
Barometric pressure : 99 kPa
Compressor status : OFF
Front left height sensor : 0 mm
Front right height sensor : 0 mm
Rear left height sensor : 1 mm
Rear right height sensor : 3 mm
Height sensor supply voltage 1 : 5 V
Height sensor supply voltage 2 : 5 V
Lateral acceleration : -0.03 g
Levelling in progress status : NO
Pressure sensor supply : 5 V
Exhaust solenoid status : CLOSED
Front left damper solenoid valve output control : CLOSED
Front right damper solenoid valve output control : CLOSED
Reservoir solenoid status : CLOSED
Rear left damper solenoid valve output control : CLOSED
fear right damper solenoid valve output control : CLOSED
Vehicle speed : 0 km/h
Battery Voltage : 13 V
Pressure sensor : 6.6 bar
Engine speed : 669 rpm

Here's some consistent data I'm seeing under normal flat straight road conditions when I get the Damper Firm Error YES:

Rear left height sensor : 3 mm
Rear right height sensor : 14 mm

Rear left height sensor : -2 mm
Rear right height sensor : 15 mm

And when I get the Damper Firm Error NO:

Rear left height sensor : -1 mm
Rear right height sensor : -1 mm

Rear left height sensor : 6 mm
Rear right height sensor : 2 mm

So I'm beginning to wonder if I don't have a bad/sticking sensor on the right rear....

 

Two new ones wouldn't require sale of a firstborn, but... AFAIK they are "Hall Effect" and tend to last a long, long time?

Meanwhile .. how "level" is your "level" road?

'Static' test, only, but..

What happens if you run one rear wheel up onto a known amount of lift?
Then the opposite wheel.

I'd use cuts from wooden boards, for a test. EG: making sure the sensor 'tracks' which side is lifted, and if by the same amount, each side.

 

Level in the sense that I take the reading from the same stretch of road and get fairly equal readings either side after error NO comes in. When YES, it's that major difference... At this point I am thinking of just "tricking" the system when calibrating and telling it it's lower on the rear right by around 10mm and see what happens. Worse case I calibrate again after....

"making sure the sensor 'tracks' which side is lifted" I'm going to do that in a short while. Driving out of my driveway should offer plenty of movement.

Thanks!

 

"one hand washes the other.." ... I'm following a month or more behind you AKA I'm but 'half way there..' as I have only installed the Suncore's on the front, which shares the ONE sensor input, both sides.

Some time after I sort some presently far more annoying underhood issues, I'll get new rears onto it, and may THEN have the exact same issues you've been sharing!

 

Well there's something to look forward to lol!!

So I took the car out today looking at live data as mentioned, both rear sensors measuring inputs as I drove down the curb. So nothing sticking... Funny thing is yeaterday we started getting into the 30's C and today is even hotter. Yesterday I went form 10 minutes of hard riding to 4 and today, down to 2 minutes.... Could something need warming up before it gives the system correct data? Maybe I'm just clasping at straws!

Next is going to be calibrate again and see if I can get the rear to finish up equal side to side. See if that changes anything.

 

Only sorta-kinda.. My Suncore struts do not have the Bilstein & Meisler ECATS damper modulation valve. Basic ignorant air-strut, only.

So:

- Height reporting we can compare.

- Calls for damper modulation, OTOH? They'll still be 'requested'. To the extent that reflects in things I can read with the iCarsfoft V3, I'll see similar.

Actual road handling will be indifferent, given the 400 Hz commands will only be warming a resistor!

 

So this morning I've been out with the old girl and after a couple of minutes, she softened up nicely, just like yesterday (external temps make no difference, much cooler today). It does seems to have improved since I did the last calibration so I'm beginning to think she just needs a solid calibration that doesn't end up giving me a drop on one side at the rear!

I'll try to get round to it this weekend or maybe just leave it be for now as it's only firm for a few minutes after resting overnight. Can live with that! See if anyone else has some input first...

 

Go figure they name a motorcar after a mammalian apex predator and .... it exhibits 'morning wood'?

 

Hi Jason,

I am in a hurry this morning and haven't had a chance to ponder your symptoms, but I can offer a few quick thoughts. First of all, to add to h2o2steam's helpful input, the default CATS state of the air spring/damper units is firm. To command the units into soft mode, the ASM sends a 5 volt 400 Hz PWM signal to the solenoids. There are only two modes, firm and soft, with no graduated settings in-between. Off the top of my head, vehicle speed is the primary trigger. I think I explain some of this operation in the post at the link below:

Air Suspension & ECATS System Summary: Components & Operation

Regarding your air leak, the most common points are the air hose fittings, the O-rings for the brass pressure-retention valves, and the exhaust valve and/or leaf valve in the compressor. If you did not trim off 5 mm of hose and install new brass compression rings (olives) when you installed your new struts, you may have slow leaks at the air hose fittings.

The O-rings on the pressure retention valves are easily replaced but removing and installing the valves requires either the correct special tool or some creativity. I have done it with pliers but that does mar the brass. You can grind an old socket so it has two prongs that will fit the slots in the valve.

The exhaust valve on the side of the compressor and the leaf valve at the cylinder inlet tend to corrode and lose their ability to seal. It would definitely be worth servicing your compressor with a new bagpipingandy or Wabco piston ring/seal, and while you're in there, clean and test the exhaust valve and clean the leaf valve.

Cheers,

Don

 

Thanks Don, very helpful. I need to dig deeper and see what the various speed sensors are doing, make sure everything is working. See what voltages I'm getting etc.

And for sure, I have the bagpipingandy kit and will install shortly. I'm also worried I ran these dampers bottomed out when the Miessler procedure says you can't but how in the H can you get the compressor out of jacking mode if you don't move the car!?