It has been a while, and many problems have come and gone on my XK8, but the stiff suspension is still there.
I have been looking through the forum today, and found a thread where there was a connection between the ABS module and possible CATS issues.
I have had the ABS module renovated, could that have any connection to my stiff CATS suspension?


I do not have any faulty message on the dashboard, and I do have 12 V coming to the active suspension control unit in the trunk.
If I disconnect a front shock the faulty message appears, so there seems to be some sort of life in the unit.


Anny help would be greatly appreciated.


//Daniel

 

What MY?
Perhaps since the repair to the ABS Module, the CATS system is functioning normally for the first time since you have owned the vehicle? My 2003 XKR Convertible can 'feel' a bit bouncy to me, at very slow speeds, but that slack is instantly taken up the moment I touch the accelerator.

 

Just out of curiosity, how can you tell if the suspension feels stiff. I have a 2004 XKR with the active damper setup and it feels stiff or hard all the time regardless of how its being driven. I'm sure even when on the soft setting they are not designed to ride like a Jaguar saloon car.

As I said before, I cannot feel any difference between soft or hard setting and like you, I have no error messages or codes unless I disconnect a damper lead connector which suggest the system is working as it should.

The only other things that spring to mind are dried out bushes or seized wishbone pivot bolts ?

 

You may want to check the accelerometers and see if they all give the same ohm reading, it's possible one went defective ? I believe there are 3.

 

Hi,
Thanks for all replies!

When I first bought the vehicle I was suppriced how nice it felt when running over rails and onto bridges, and still stiff when I drow fast on winding roads, so the suspension system with CATS did work back then. It is a clear difference as from how it is now.

I have meassured the output from the accelerometers and they seems fine (refering to some other post where the walues was given) Lateral 1,6V and the two vertical 2,5V.
I did not meassure the resistance though.

Have any one out there had their ABS module repaird and then used on a XK with CATS?
I really need to fix this suspension system issue as it is driving me crazy :-)

 

Here is the pinout of the Module in the rear, you may have this since you measured the above sensors (btw your voltages are swapped, Vertical is 2.5 lateral 1.5). I see two signals that could cause a issue, Pins 2, 24 and 26 but if there were some issues with these I think it would throw a code. You could if you can try swapping out the ADS module IF you can I see you're in Sweden and maybe not many xkr around. Try pullling the front wire from one shock and see if you get the error message.

To be honest I'd never noticed that much difference, since the firmness would kicking under harder acceleration / driving. I did notice other suspension wear that caused me problems.

 

Did you perform a 'hard-reset' after installing the re-conditioned ABS Module to clear any 'ghost' issues that may still be floating around the car's electronics? If not, it is worth a try and will reset most everything back to default; it may be the 'kick in the chips' the CATS needs. There are procedures for the hard-reset, basically just holding the positive and negative clamps together, removed from the battery, for ~10 seconds, then let it sit for 30 minutes, reconnect the battery and follow that procedure, it is several steps in length and will enable you to skip over some re-learning the car would normally have to go through for the first 10 or so, drive cycles.

 

My CATs feel excessively stiff all the time too, I'm almost looking forward to a hard failure so I can swap out for regular shocks.

 

Thanks again all of you out there trying to help me.

I have done the hard reset, and it did help with some other issues + gave a much better gear shifting quality (I have also changed gearbox).
I was really hoping for that to also help with the CATS-system, but no change.

By the way, is there any good/cheap faulty code readers out there that can read chassi faults? The one I have (Torque Light) only gives P-codes, not C.

 

I have meassured the voltahe on the pins of the CATS module.

I attach a picture of the results. Anyone that knows if the figures make sense?

And the faulty message shows up if I disconect a shock, so there is still some life in the system :-)

 

Now i'm speculating here as i haven't actually done any kind of diagnostics on the cats module but.
The main issue is that you would pretty much need to measure the control signal to the dampers while the car is moving in order to test if they are switching to the soft setting.
From what i have read the default mode (this includes standstill) is stiff/"solenoid off".

Now looking at the values you have measured i would have expected the "Damper Control Signals" to be 0v and not 14,1 however the effect in real life is the same as there's no voltage differential so this may very well be by design.

I would suggest that you try to get a measurement of one of the positive Damper Control signals while the car is moving. 10mph should be plenty sufficient to have the suspension switch to soft mode.
(yes i know it's a lot harder in real life than it sounds.)
Also if you see something like 5v while performing this test don't be alarmed and jump to conclusions. That would indicate that the module is powering the solenoids by a PWM signal which is fine.

I read a forum post on an X350 where this was the case but as i haven't actually tested this i'm merely pointing out the possibility.

Happy hunting.
/Stig.

 

On another note.
Where in Sweden are you?
The only reason i ask is that i'm in Copenhagen and would be happy to offer you a diagnostics session.

I have a fully functioning IDS. (dealer diagnostics software) which will read C codes but the CATS system is as far as i know a stand-alone system. e.g. not integrated into the rest of the system so i would not expect to see any other codes than the one general fault you already experienced when you pulled one of the leads for the damper.

Best
/Stig.

 

QUOTE: 'I have done the hard reset, and it did help with some other issues + gave a much better gear shifting quality (I have also changed gearbox).' END QUOTE.

Does the CATS interact with the transmission, does it communicate to and from the transmission, does the CATS plug into the transmission, and most important, was the problem with the CATS present before the transmission swap? Is there any difference in transmissions setup (mapping) to operate properly with the CATS System present? I do not think CATS was available on the earlier model years; is it possible the transmission you have is from a pre-CATS vehicle, and therefore does not communicate with CATS, or would it make a difference?

BTW what model/year is the vehicle? Different models XK8 or XKR, and years had different options and capabilities.

QUOTE: 'I have had the ABS module renovated, could that have any connection to my stiff CATS suspension?' END QUOTE.


Was the problem present with the CATS before you had the ABS Module repaired? Did you clean the 'vehicle' side of the connector before re-installing the unit, and have you checked to make sure the plugs are fully seated, and that no pins or sockets have receded into the connector or bent, and checked any fuses or relays involved? Since the ABS unit was removed and re-installed, did you have the brakes bled? I do not know if bleeding the brakes would have any effect on the CATS, but in these cars you never know.

And finally, was the battery connected when you plugged the ABS Module in? If so, it may have 'fried' something else in the module.

 

Thank you very much for the offer Stig!!
I live just outside Stockholm, so 600 - 700 km to Copenhagen :-)
So I guess it will not be possible for you to help me. But thanks for the offer, I really appreciate it!


But I think I will try to have possible codes read by a Jaguar dealer, just to make sure that I know if there are any codes lurking in the system.

 

[QUOTE]

Does the CATS interact with the transmission, does it communicate to and from the transmission, does the CATS plug into the transmission, and most important, was the problem with the CATS present before the transmission swap? Is there any difference in transmissions setup (mapping) to operate properly with the CATS System present? I do not think CATS was available on the earlier model years; is it possible the transmission you have is from a pre-CATS vehicle, and therefore does not communicate with CATS, or would it make a difference?

BTW what model/year is the vehicle? Different models XK8 or XKR, and years had different options and capabilities.
END QUOTE.


Thanks for the ideas.
I have read about the CATS system and as it seems it is a stand alone system, just relying on the three accelerators + signals from speed and breaks, so no connection to the Gearbox or engine control units.
I am not sure how the signals from speed and breaks should look, and I have not been able to set up a way to measure while running the car.
It is an early XK8, from MY 1997, but many of the castings are from 1996. But it was sold with CATS.


It has been a troublesome car, so I do not remember when the CATS issue occurred in comparison to the different things I have fixed.
I bought it with some faults (chain rattle, handbrake, ABS fault, and some more I forgot).
I drove it gently from the seller back home, appr 500 km, and during that drive the suspension system impressed me.
After I fixed the chains and tensioners I tested to push the pedal to the metal for the first time, and then the gearbox gave up. The classic fault by losing 1:st, 2nd and 3:rd gear.
After that I fixed the ABS module and handbrake.
Come to think about it, it might be that the CATS system was still working after the gearbox change.
I showed the car to a friend of mine just after the gearbox change, and I don't think I mentioned the CATS system that time - a clue perhaps? (that was the first time I properly tested the car)

 

Many ideas, I appreciate the effort, sooner or later there will be a eureka moment I hope.
The connector to the CATS module looks really fine. No corrosion or anything like that. Still I have used connection cleaners just to be sure.
The pins are straight and the plugs seems to be fully seated (have tried to push them from behind when connected just to see if I could move them further.
Fuses and rely seems to work, maybe I should double check the relay once more, I think I swooped it once, nut I am not sure. Onto my "to do list"!


When I changed the ABS unit I did not need to open any of the pipes to the break system, so there was no need for bleeding afterwards (it was tight but it works - there is a thread about it somewhere in the forum that I used as guidance).


Yes, the battery was connected when I worked with the CATS module. Both connecting and disconnecting it. I am a mechanical engineer, so the electrical stuff is a bit strange to me :-)

 

What you have confirmed by measuring the voltage of the -ve side to ground is that you don't have an electrical fault I think the solenoid circuit. The control switches the signal to ground when it goes "active" so at that point you should see 14V at positive and near zero at negative.

If you get an error condition when disconnecting a shock, then the system is likely functioning correctly.

The one that might look off is the Trac Override on pin2. I say that because the other inputs, 24, 26 are normally high and grounded when "true".

The schematic I have (2003) doesn't mention pin2 at all or show any connection to the ABS, but since you mentioned working on the ABS electronics recently, that raises the question. If this were permenantly grounded for some reason, you might be stuck in "firm" mode because the control thinks the traction control is active.

Firm just effects the valving on rebound, by the way, which is I think why people sometimes describe the firm mode as bouncy.

With the car completely off and key out you might try measuring the continuity of that pin to a chassis ground. Check with the abs module connected, with the ABS module disconnected and both modules disconnected.

It's possible you've gotten a short to ground somewhere in the harness but with Both ends disconnected, it should definitely be an open circuit.

 

Thank you!
I will try to do this, and perhaps even try to give pin 2 some 12 V to see what hapens (I will start by meassuring).

I hope to have time some evening this week. I come back with results.
/Daniel

 

The following is Jaguars description of the CATS active damping system. Interestingly, it says when detecting bumps or depressions in the road, the dampers are set to the firm setting. I think your system is working correctly as it should feel firm driving over uneven surfaces.

Operation
The four adaptive damping units are simultaneously switched to either firm or soft setting to suit circumstances. When the vehicle is stationary, the system adopts the firm setting to minimize vehicle pitch during initial acceleration. From 8km/h (5mph) upwards, the system reverts to the soft setting until otherwise switched by the ADCM.
On detecting cornering forces, the lateral sensor transits signals to the ADCM, which in turn switches the damping units to the firm setting, reducing vehicle roll-rate and improving wheel control.
On detection of a bump or depression in the road, the vertical sensors transmit signals to the ADCM, which in turn switches the damping units to the firm setting to minimize vehicle body movement.
Under braking conditions, the ACDM, on receipt of a signal, commences calculation of vehicle deceleration. When deceleration exceeds a pre-determined threshold, the ADCM switches the damping units to the firm setting, reducing vehicle pitch rate and improving wheel control.
Following completion of a cornering manoeuvre, negotiation of road surface undulations, or heavy braking, that has necessitated switching to the firm setting, the ADCM always returns the damping units to the soft setting.
In the event of failure of the Adaptive Damping System, the damping units automatically revert to the Firm setting, ensuring that the vehicle remains safe to drive under all circumstances. The driver will be alerted to such a failure by illumination of a 'SUSPENSION FAULT' warning on the fascia message center and the amber warning light in the instrument cluster.

 

My read is different. Reading the '03 Electrical manual (I realize yours is older), the Adaptive Damping Control Module is clearly on the "bus". In addition, the Appendix that lists the CAN message receivers has tons of entries for this module. I assume that if this module is not receiving a message it expects in a timely manner, say, from the ABS module, it would consider it a "fault" and go back to defaulting the shock to stiff.

You might want to locate the electrical manual applicable to your car, and see if any of this applies. Check jagrepair.com

At this point, after having done the basic electrical sanity check, you might be best served by letting the module itself tell you what it thinks. I mean a quick session with a proper scan tool might tell you a lot.

AFAIK, the car has a total of 3 data communication protocols in place for all the modules. All 3 protocols separately go to the diagnostic plug, so you need a scan tool that can interface over all 3 protocols to get a clear picture.

Best I can figure, this particular module receives CAN messages, but is able to communicate over Serial Data Link, I suspect for diagnostic purposes.

Best of luck, keep us posted.