Hello everybody!

My X350 (XJ8 2004) developed interesting problem. About a week ago I had the typical air suspension fault some minutes after start-up, with yellow light, which went away after 4 short drives on the same day (don't know the exact cause for fault message, but ride height was OK all the time and there was no suspension low warning or red light).

I know that the CATS is separate from Air suspension system, but it goes to hard mode when there is air suspension fault.

However, what happened to me; the CATS stuck to hard mode even after the air suspension fault and yellow light were gone. Ride height is exactly normal, so this in not problem with air suspension. The car has very harsh and hard ride now, unbearably so.

I tried to reset CATS by disconnecting battery for 10 mins, but no effect. Still in hard mode.

Any suggestion how I could reset the CATS and possibly air suspension module without dealer data link? Would not like to pay dealer 100 eur for connecting a computer and pressing a button.

Thanks,

 

Hmm... Might be best to clear the problem with the air suspension first. Get the codes read, but it will probably be the air compressor is on the way out, (normally code C2303).

 

Thanks Fraser, but this was not the answer I am looking for... The yellow light and air suspension fault are gone, no warning lights, nothing, just CATS stuck on hard.

Or is it so that the air suspension fault is saved in memory, even with no yellow light and warning? And this is causing CATS to default to hard mode?

It seems to me that co-operation of Air suspension & CATS are impossible to find from any forums. After all, they are two separate systems. There must be experts in this forum who know about their interaction, and what could cause CATS default to hard mode with no warning lights or messages.

 

Well usually you will get a CATS SYSTEM FAILURE message along with the yellow light, if something is amiss in the CATS itself. Since you don't have that then you really need to get the codes read. Or try leaving the battery disconnected for a longer period (i.e. overnight).

The CATS solenoid in each shock is driven by a 5V pulsed signal, if that voltage is not there (i.e. by some kind of fault) then the shocks default to firm mode. BUT if there was a fault then you would get the error message. Likewise if the solenoid went open circuit.

By the way, welcome to the forum, why don't you stop by the new members section New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum

Also would help if you could put details of your car in your signature.

We also have a Regional section for Europe (see the link in my signature).

 

Thanks, I did the intro and updated signature.

About the fault itself. In the Air Suspension fault monster thread, I saw somebody else was complaining about same issue - he once had Air Suspension fault light which went away, but the CATS was stuck on hard mode forever. He was not able to elaborate on the issue and did not know CATS by name, it seemed, but the fault itself sounded similar to mine.

I will get dealer to check the codes. My OBD2 scanner does not show anything. No warning lights are on so I hope there is some codes to read for the dealer. Can somebody tell me if X350 keeps the faults in memory even if the yellow light is not lit?

 

Answer is yes. However, I'm not sure about the relationship between air suspension faults and CATS, but it appears from your experience that there is a link. There may be a counter that releases the CATS after a set number of successful air suspension start-ups (on engine start), but I'm guessing on this one.

 

And now, I have full explanation.

First; I think X350 air suspension / CATS faults, and symptoms, would command an own FAQ. At least for me it was not pleasurable reading monster thread with many unrelated comments, and trying to find similar symptoms to my own situation. Many of us don't have own IDS available, so faults and symptoms should be described in laymans terms, I think.

Let me start with mine:

Symptoms:
"Air suspension fault" + yellow light in one start-up. All the time normal ride height - no other warning messages. Yellow light and warning message vanished after 4 or 5 short drives during the next 24 hours.

BUT! CATS (active damping) remained in hard mode even after several days of driving. Car was very rough and harsh to ride, like riding Toyota Corolla. Ride height was normal all the time.

Correction: Went to dealer and asker to zero all suspension error codes from memory. They were erased, and voila: silky smooth ride was back without any mechanical work.

Actual technical cause: (this was the bit of knowledge that was not available in net, until now with this writing):
A bit weak air suspension compressor threw C2303 (Reservoir playsability error) in one start-up. Following air suspension fault commanded also CATS to default to hard mode. For this specific ASU and CATS SW version and combination of different systems in my 2004 Jag, CATS was locked in hard mode as long as C2303 was kept in memory - even when warning light and user message were off long time ago. It is unclear whether these other ASU (air suspension ecu) messages had something to do with it also: B1671, U1900, U2581. These were also deleted.

So if you think your car "feels" harder on the suspension, it may be true - sometime in history you may have had air suspension fault, and CATS is still in hard mode... This is difficult to diagnose for layman without special tools (if you don't disconnect the CATS wires from struts and drive it then comparatively), so you need to trust your feeling.

So, this is another Catch 22 - Gotcha from Jag. Thanks, Jag engineers.

 

That was a very interesting explanation, and goes some way to explaining my own problem of 2010, when I got the 'air suspension fault' in late autumn.

In my case, I quickly replaced the air compressor on advice from the local agent, but before I took the car in, the technical guy told me that the suspension was 'locked' by the ASM until the fault codee was cleared. I understood this to mean that the air in the springs was locked in by the valve block, but it seems it also defaults the shock absorbers to 'Hard' setting. However, I didn't notice anything hard about the suspension at the time, however the car is a 'Sport' with harder air springs, so maybe I just didn't notice.

 

My 2005 vdp just had a new arnott compressor installed and all the asu warnings are gone, car at nominal stance height etc. I replaced the pump at home. No problem. Took awhile to pump up the system. No big deal.

Now, I am wondering about the ""harsh ride". Not positive I have it, but could I just disconnect the wires to top of struts, go for a ride and see if it is smoother? ( front only). If it is, then I have same problem as joseee. Then would proceed to dealer to have codes erased... Or is there a better way?

 

N9921x, I did not find a better way than dealer visit. If you have doubt that ride may be harder, I would go to dealer to erase the codes. It is quite certain there is error code in memory. Like already mentioned, even if no warning is shown, codes stored in memory can lock CATS in hard mode.

If you disconnect the wires the ride should be harder, not softer. If no difference is felt, then CATS was already locked in hard.

After further study I cannot tell what would happen disconnecting the wires. One thing is for sure, then CATS and maybe also ASU will default to some error mode (and there are many different "special" modes they can default to), and also that may change ride characteristics. CATS and ASU are interconnected (via CAN I think), so their errors can effect each other.

Gotscha.

 

I have seen this gremlin before do to a weak air suspension pump...and a generic obd2 scanner wont read suspension perameters...This is why I purchased the LAUNCH X431 this unit will read such codes and reset the suspension codes,nice unit....Glad you got it fixed...Thanks for the write up.

 

jossevee how is the car now? Did you have to have the compressor replaced? As a new owner of an X350, I too am having the dreaded suspension fault come and go. Took to my local garage to have codes read (not a Jaguar Agent) and code P1672( communication error) appeared but no C2302 or C2303 which are the air pump codes
The local garage has the Jaguar software on his scanner but I,m wondering whether it can access all the codes. I am trying to gather as much info as possible before biting the bullet and have a new air pump. Thanks for your very informative input and interesting read

 

The air suspension pump loses it's efficiency because the piston seal wears down with use but replacement seals are not available since Wabco and Jaguar like to scam their customers.

Two years ago I had the air suspension light come up and it was on all day.

I removed the compressor and removed the piston seal (easy) which is a split seal,
I then gently stretched the seal open at the split and replaced it in the compressor.

I kid you not that was 2 years ago and no more amber light.

BTW I lived in Hythe for many years!

 

If only they did a seal kit! How long ago did you live in Hythe?

 

"replacement seals are not available since Wabco and Jaguar like to scam their customers."

Seals are available for the Range Rover for about 30 GBP also why does Denso who make the TPS and throttle bodies have to sign an agreement with Jaguar not to allow the TPS to be sold separately??

It can only be so that owners have to buy the whole lot!

I wonder if there is a law against this practice in the US?

It annoys me that Wabco don't even call it a compressor, they call it

an air supply unit!

We left Hythe three years ago and miss day trips over the Channel to La Belle France!

 

V8junkie, the car is OK for now. Weak compressor throws amber after 10-15 min stops with warm car, never on any other occasion. I have additional info on cats behaviour, it appears some error combinations leave it in hard mode forever, some just for duration of amber light. I had to zero the codes one more time at dealers...

I am devicing a simple tool that can be used while driving to check if cats is hard or not. I am also in process to find cheap tool to erase suspension error codes myself. If I dont find it, I am tempted to crack the protocol with official unit and rip parts I need to zero them with normal obd scanner. I am not saying that I would do it as it might be illegal in some countries, just that I am tempted...

 

jossevee, did you ever find a way to reset/correct 'Cats stuck in hard mode?' LOTS of 'claw' people are interested, whether they read your post or not. I need this info for my 2003.5 VDP. The trip to the dealer is OK once, but what if problem returns?

Sincerely,
Dsims6465 (The Old Black Guy)

 

Usually if the module has been cleared,and the unit has no plausibilty codes(air pump related) and the piping and shock towers have been thoroughly checked for leaks, then 9 times out of ten it is a faulty suspension module.If memory serves me correctly the 2004 has 4 sensors one on each wheel for height but the 2005 has just three being compensated for the leveler in the headlight unit.If all codes have been cleared, and another test that can be done is jack the car up on one side for 5 minutes,then lower it to force the retention tank to empty and level the car..if the tank does not react,then that lets you know that there is no communication from the module with the height sensors. Hope this helps, until next time happy wrenching...

 

Just a note...if you want to clear all codes and don't want to visit the dealer, most codes can be cleared by disconnecting the battery for 15 minutes.

The down side is that you have to reprogram the clock...and the tranny will shift hard for a few miles while it relearns.

John

 

???
I allways read that you cannot reset the tranny by disconnecting the battery.. you have to use the IDS/SSD.