To me it wasn't surprising that both front shocks were low. The car seems to keep them in sync at the same height. That is the impression I got when jacking the car unsymmetrically.

The location of the air escaping front left was indeed nothing I would bet my car on.
I sat in front of the wheel and with closed eyes, I had the impression of the sound to be in the middle of the wheel house.
.. but I have no reference sound how the compressor output compares..

I contacted my dealer when the car was sunken down... but now it's hard to claim warranty.. as everything seems to work again.
I'm nut sure if I wish the problems to come back to have them demonstrated or not ..

 

Yes, if the system regulates the height it does, but not when you have a leaking shock. My right shock is leaking and the right side sags a lot faster then the left one. The reason the left also sags is that the weight of the engine is to much for the pressure in the one shock.

Just out of curiosity, what was the reaction of the dealer to your call? Did they offer to fix it? What you maybe could do is to get the dealer to acknowledge this problem has occurred within the warranty period and remain the right to get back on this issue if the problem reoccurs. I would at least talk to them what happened and see what they offer to do now.

Guus

 

After suspecting my front shock, I must redraw this suspect and point towards my ASU, the Airsuspension Steering Unit.

With SDD I gave the command to empty rear shocks, which worked.
The valves were steered by 12V and current was about 1.7A total.
Now I emptied the reservoir. Same voltage, but 0.9A.
Last not least I commanded front shocks. 0.05A, 0Volt steering power. !!
The same command worked before.

A ASU, that has become nuts, would explain everything to me... the sudden appearance and dissappearance of strange effect...

I'll check my warranty status now... but I hope this was the last turn of this story...

 

Sound more plausible but also check the front height sensor(s). Maybe these caused a short circuit in the ASU? Still looking for a reason...

Guus

 

One more excessive test session later, I learned a lot.

As the "emtpy front shock" command doesn't work, I tried to test whether it can release air.
So I went on german "autobahn", speeded up to 200km/h with SDD datalogger active.
I can see valves open and a height decrease on the rear is visible in the height sensors.
On front, I cannot see the reduced height.

Now I remembered, that my ais suspension allways released air when I tried to jack the car. So I started jacking.
Immediately the car released air to stabilize... then I quickly removed the jack and it gained height from the reservoir.

I even opened the air suspension module and checked the mosfets .. it seems like the controller doesn't steer them.

All my height sensors show plausible values. The only defect I can catch at the moment is the failure to release pressure on front shocks with SDD.
I have no clue what might be the cause of this story...

 

Hi nebelfuerst,

When you see the valves open in SDD, I assume that doesn't necessarily mean all the valves are responding correctly. Could it be that the valve for the front shocks is mechanically restricted and not opening properly? Given all the things you seem to have ruled out, I keep coming back to the valve block as a suspect.

Cheers,

Don

 

+1 Don

You could disconnect the lines going to the front and use the SDD to trigger the front valves. If the valves are open according to the SDD you should feel air from BOTH lines. Although the fronts act as one they are two separate systems and it knowing if both are non working or just the one might help diagnose the problem further.

Guus

 

I don't plead guilty for my valve block... yet.
When sending the command to empty the front shocks with SDD, I can measure, that there is no 12V present at the according valves.
I traced through the ASU's PCB and found a MosFet to be controlled by some 74HCT86.
The inputs of the 74HCT86 are correctly converted into the steering of the MosFet.
I guess, the input of that is coming out of the microcontroller of the ASU.

So my options are now:

- Some strange SW-fault or HW-fault within the ASU.
- Some unknown rule within ASU, that prevents command to run.
- Some bad sensor-value to the ASU, which prevents it to do it.
( All height-sensors are plausible, and pressure is , too..)

I probably try to get my hands on a replacement ASU.
Does anyone know if you can swap it easily ? Is some SDD-action required to integrate the new ASU ?

 

If you're at this point why not try to reflash this ASM with the SDD?

Yes you do.

Air Suspension Module
The air suspension module (ASM), which also controls the adaptive damping system and provides height sensor information for the automatic headlight leveling, is located behind the rear seat. The ASM provides a number of air suspension operational modes dependent on the vehicle state; refer to Operating Modes and Strategies.
ASM hardwired inputs:
• Height sensors
• Valve block pressure sensor
• Vertical accelerometers (adaptive damping only)
• Valve block solenoid control
ASM inputs, via the CAN:
• Vehicle speed
• Engine speed
• Engine torque
• Lateral acceleration
• Steering wheel angle
• Steering wheel velocity
• Brake line pressure
• Ambient temperature

The ASM will require calibrating using WDS if:
• the ASM is replaced;
• a height sensor is removed and reinstalled;
• a height sensor is replaced.
Refer to ‘JTIS’ for further information.

Guus

 

Don't forget to check the ground point of the ASM.
I guess it has no ground point of its own but uses the ground point of the rear power distribution fuse box.

Ground points are common causes for sporadic failures.
In my X350 they killed at least 5 controller modules in 7 years:
Headlight, cooler vent, trunk actuator, alternator, rear power distribution fuse box.

It is possible that your ASM recovers after some days without current.

Cheers

 

Good suggestion.

Guus

 

Leo,

You are right! The grounds on the X350s use aluminum nuts and eyelet terminals on the wires, so the corrosion is whitish and not as obvious as typical red rust on steel terminals, but it's every bit as resistive to current flow.

The ASM does have a dedicated ground, which is behind/below the rear seat on the RH side, ground G17, shown in Figure 05.3 in the Electrical Guide. While cleaning that ground, it would also be prudent to disconnect the ASM connectors and flush them out with zero-residue electrical contact cleaner.

Cheers,

Don

 

I checked all contacts and used some contact spray on them... doesn't change anything..

I had a hard time to identify the correct plug, as there seems to be no label on them and they use the same color wires on different plugs on the same device...

 

Hi nebelfuerst,

I can't recall which component you were cleaning the electrical connectors on - was it the Air Suspension Control Module (ASM)?

The Electrical Guide shows the code names for each connector on the ASM and the schematics show those code names to indicate which wires attach to each connector (and which pin). You can download the 2003.5 Electrical Guide from the X350 'HOW TO' quick links, but I don't see the 2004 guide available right now. If you need the 2004 guide but don't have it, send me your email address via private message and I'll email it to you in pdf format.

Cheers,

Don

 

Yes, it was ASM.
I attached a foto of my connectors of ASM.

I read, that one connector must be CR91... but neither on the plug nor on the cable I can read "CR91".
So I ended up measuring the resistance of wires between ASM and valve block to identify the correct plug.


Slightly OT:
I opened my ASM and recorded with IR-Cam to see what Mosfets get hot when emptying different parts of the system.
See pic.

It's pretty hard to reverse engineer the ASM. Is there a schematic available ?

 

Hi nebelfuerst,

The actual connectors are not marked with those numbers; the numbers are strictly schematic identifications. Page 31 of the 2004 Electrical Guide (page 33 of the pdf document) shows a diagram of the ASM and identifies each connector. CR91 is the largest connector with 18 pin locations (I don't know if all 18 locations are used). Also, on the page before each electrical schematic is a list of components, connectors, relays, grounds, etc. For example, on page 76 of the pdf document in the list of components for Figure 05.3, CR91 is identified as an "18-Way / Black" connector attached to the Air Suspension Module.


I haven't found one, but you might search the various Wabco websites in case I missed it.

Cheers,

Don

 

I'm using the 2003.5 or the 2004 Electrical Guide from Jtis installation..
The page numbers do not match with yours. The word "black" only appears at the definiton of wire-color "B".
Where does your 2004 Electrical Guide come from ?

 

I think my 2004 Electrical Guide came from the Captain Jaguar website before it went down. I'd be happy to send it to you so you can compare it with the one you have. Just send me your email address via private message.

Cheers,

Don

 

From your earlier posts I understood that the problem itself was fixed but you were thinking how to get suspicious parts replaced under guarantee. Right? Any update on that?

Guus

 

I told my dealer when the problem happened, but didn't hear much response yet.
It's probably hard to claim warranty when the car drives normal and there's just one SDD command that behaves different...
Now warranty is over, so I'll build my own backup in case this prob will reoccur.