I have always felt my CATS suspension is too firm and I am investigating how to check this. It's an XK8 MY2000.

I have read the various posts about this as best I can and have checked the two fuses (2 & 4) in the boot/trunk (I have seen reference to fuses in the engine compartment but they seem to have no relevance), I have checked diagnostics I1, I2, I3 for voltage supply to ADCM and the resistance and they are all OK.

I pinched the idea of using a voltmeter on the front shock but adapted it to connect an LED to light when voltage was sent to the front shock on pins 30 and 31 on the connector. My understanding was that firm is 0v and soft was 5.7v. But on my test run the LED was always on and looked suspiciously like 12v bright not 6v which is rather more dull as I have a resistor in the circuit. Anyway clearly pins 30 & 31 had voltage across them that would illuminate an LED quite well all the flipping time and hence imply soft.

I'm obviously doing something wrong and have misunderstood something.

Can you help me out please?

I am now going to move on to the accelerometers and test their voltage as best I can. With a heavy heart I suspect it will be the speed wire that's faulty.

 

Doc,
The EG implies that the voltage across the shock solenoid is 12V when active, 0V when inactive.

Do you have the WS manual as there's some explanation in there? I've attached a snippet that might help.

 

Thanks Michael, I have those pages and have been following them. I didn't check the electrical guide but I will.

When you say 12v when active do you mean firm or soft?

And I have just come back from a long walk and decided that I can't trust my LED so I will run wires from the boot to the cabin for a multimeter and get a friend to watch the readings as we drive.

My thinking is that if I can get the CATS working OK then I'll tackle the top rear shock mounts, if I can't get the CATS working then I'll put standard Bilsteins all round.

 

When I tested mine, the multimeter was connected at the shock absorber end, not the control unit end, so you may well read a higher voltage than I did. Either way the fail safe mode is hard, so 0v = hard, 12v (or whatever) = soft.

An LED isn't the best way to test a circuit like this due to the tiny load it gives - a 12v bulb would be better and you really need to be testing at the shock absorber end to see what the shock is actually getting.

My posi-taps are still connected to my shock wires under the plastic dome, ready for testing in the future - I ran a long wire back to the dashboard so I could watch the multimeter as I was driving. It's a shame Jaguar never fitted a tell tale as standard.

 

I'm glad you've popped up. I wondered if your 5.7v was due to being the shock end.

I see what you mean about reality being at the shock so maybe I'll get some small posi-taps. I tested some scotch blocks on a test wire and they were useless as the wire was so thin as is the case at the shock.

If you will permit a dumb question do posi-taps come in different sizes, it's not plain to me if they do and if they just how tiny I want them to be. Those wires are thin!

 

If the CATS are always on firm mode you will know, I disabled mine and it was terrible. It didn't feel save going above 20mph on a rough road. I think when I replace the shocks I will upgrade to standard shocks, I don't think CATS make a big enough difference.

 

The posi-taps I used were the blue ones - they do come in different gauges. In fact the listing is still on eBay for the ones I bought 6 years ago:-

https://www.ebay.co.uk/itm/300915885...mis&media=COPY

 

I feel safe enough it just thumps more than I feel a Jaguar should. Of course it may be the rear shock mount bushes but I don't think so. It never varies it's always thumping. I'm not convinced they make enough difference for me.

 

At the risk of stating the obvious, the more immediate diagnostic would be to procure a Jaguar/Land Rover code reader and ask the module what it thinks is wrong, and provide you with searchable trouble codes. At least initially it could point you in the right direction.

Also, keep in mind the shock could be controlled by the module with PWM for a form of continuously variable control instead of a simple on/off. IOW, the on/off could be cycled quickly, and maybe hard to pickup on an LED. Unless of course I have this confused with the adaptive steering assist...

Best of luck, keep us posted.

 

Yes, if I had access at modest cost for a proper diagnostic system then I agree that would be a good way forward. I think my local dealer would want about £150 for this and while I am time rich I am cash mean. The village garage has a very good snap-on diagnostic which interrogates you to identify which model it's dealing with but I doubt that it does the C codes which I think cover the CATS.

I think the PWM would have to be very fast indeed to cheat an LED. I worked with a guy who used PWM a lot in door locks of all things and he would use it to save battery life by avoiding the LED being on continuously. A Duracell could last 10 years in one of his locks showing an LED when the lock operated and buttons pressed. I mess about with Arduino and PWM so I have a little familiarity. But it's certainly worth a thought.

 

Thanks for that. I'm sorted then.

 

You can connect your voltmeter to the wiring at the yellow 18 pin connector at the rear of the center console. Pin 11 & 12 for the right front damper (orange/green & green/blue wire) and pin 13 & 14 for the left front damper (orange & orange/yellow wire).

 

But the challenge is seeing it in motion That said it is just a matter of running cables here and there.

 

As an experiment I connected up a 12v led to the right front shock and I can confirm it was completely off when the suspension is hard (at rest etc) and lit when moving over 5 kmh. It wasn't shining that brightly when lit, as you might expect if it isn't getting the full 12v, but it was always either on or off - nothing in between.

I would guess that if you aren't getting the Suspension Fault message you won't get any fault codes if you did scan the module. You can test the accelerometers with a multimeter to see if you are getting the kind of voltages expected when moving. The speed input is a pulse IIRC, but you would have to confirm what you should be seeing if you test it.

 

Is that connector easy to get to? I've run the wire inside the top of the wing and through the door jamb - it would be much better connected directly inside the cabin and have the tell tale as a permanent feature.

 

Yes. Just snap off the rear panel of the center console. Or take out the armrest / storage compartment assembly (four screws).
If I remember correctly the signal to the shock absorbers are 5V not 12V, you may check this out with a voltmeter before connecting a tell tale light

 

Perfect - that will be very easy to get to.

 

Dibbit thank you for the LED test.

NORXKR - so the connector in the armrest essentially replicates the one in the trunk? That would be very convenient otherwise I was planning to run temporary wires through windows etc. I am away for a couple of days but will explore!

Mike​​​​​​​

 

console connector RH12 will only give you front dampers and some accelerometer feeds, no rears.
If you really want to know what is going on AT the dampers, that's where you should be checking anyway, as you have been.

 

Thank you.

I expect the electrical guide has the pinout for RH12.