Now that I have read all about suspension faults with the cars becoming dangerously too low, I have a different problem which I have not seen posted anywhere.

My 04 xj8 rear suspension is frozen in the max extend position. It looks like the car is ready to drag-race! It acts like there is no suspension at all, more like the wheels are welded on.

I have no fault messages and no codes on a non-Jag reader. The front suspension works normal.


I tried disconnecting the battery for 30 minutes to reset but to no avail.There is no evidence of water in the trunk to cause electrical problems.

Is there any way to reset this system or release the air pressure or test the level sensor? Is there another area of the car I need to investigate for corrosion?

I am now reading the suggested "how-to" posts but any additional info will be appreciated.

 

Hi 76driver,

Sorry to hear you're having strange issues with your suspension. A typical OBDII scanner can only read some of the Powertrain (P) Diagnostic Fault Codes (DTCs). What you need to see are Chassis (C) codes, and possibly some Body (B) and Network (U or Undefined) codes. To see those you need to have your systems scanned by a Jag dealer or an independent mechanic with the dealer-level system or a high-end system like Auto Enginuity with the additional Jaguar module. If you have a laptop, for as little as USD $50.00 you can acquire a Mongoose OBD-to-USB cable clone and an older version of Jaguar-Land Rover System Driven Diagnostics (JLR SDD), the system Jaguar dealers use. Many members of this forum are using this system to do the diagnostic work on our own cars. SDD can recalibrate the ride height of the suspension at each wheel, which might be worth trying on your car.

Off the top of my head, the components involved in regulating the rear ride height are the two ride height sensors (one on each side), the valve block in the trunk under the spare tire, and the Air Suspension Control Module (ASM), which is behind the rear seat back. It seems unlikely that both rear ride height sensors would fail simultaneously, and it seems equally unlikely that the ASM would malfunction in its control of the rear air springs but continue to function normally for the front springs. That brings us around to the valve block. It might be worth checking for water pooling around the valve block and cleaning the electrical connectors with zero-residue electrical contact cleaner spray.

It seems remotely possible that the exhaust valve that is part of the air compressor assembly (left of the radiator behind the front bumper) could be seized due to corrosion and failing to open to release excess pressure, but we would expect that to affect the front end as well.

You can download the air suspension section of the X350 Jaguar dealer training manual here:

http://www.mediafire.com/view/7rdkgg...on_Section.pdf


Did any event occur just prior to the rear end misbehaving? For example, did you jack up the rear end? Hit a hard bump while driving? Drive with a heavy load in the trunk? Disconnect the ride height sensors? Have a wheel alignment, tires replaced or other service performed?

Hopefully some of our other members will offer some additional ideas.

Please keep us informed.

Cheers,

Don

 

Mine has done the same thing on two different occasions. idk what happened the first time but it fixed itself after a few startups,that was 2 yrs ago. The second time a couple of weeks ago it did it again and i discovered there was 3 inches of water in the sparetire well. Your ride height sensor might be confused, idk where that is located but i do know the Air tank and what looks like a Modulator is under the spare tire and foam blocks in the trunk. You might try unplugging it fir a minute

 

I checked out everything I could think of from water in the trunk well, in and under the rear seat and crawling under the car to look at the ride height sensors. Nothing was out of the ordinary nor broken. I disconnected the battery again to see if that would reset the system but no luck.

So I took it in to my mechanic and left it with them for a few days since they were swamped. But before I left, one of the mx said he used to work for Ford and saw the same thing happen many times on the Lincoln Town Cars which, I believe, is where this air ride system originated.

Went back a couple days later and they told me there were NO codes when they checked. It seems the controller lost all it's memory for some reason and just defaulted to filling the airbags to the max extend thereby pushing the rear end up in the air. They reprogrammed it and it seems to be working OK.

We debated what could cause this to happen. The only thing we could think of was the car battery died about a month ago and was replaced. Why would an electrical problem a month ago manifest itself this way now? Who knows but I am just glad it was an easy reprogramming fix.

 

That's great news, 76driver!

Thanks for reporting back to let us know the resolution.

I can't recall whether you cleaned the electrical connectors at the ASM along with its ground point, but it seems possible that a loss of memory could be caused by corrosion or looseness of those connections, or water shorting the contacts at a height sensor. It might be worth cleaning all those connectors with zero-residue contact cleaner spray (and a small wire brush if you find noticeable corrosion).

Take care when retightening the ground nut because the torque spec is just 6.5 lb.ft., just barely tight. Several owners have learned the hard way how easy it is to break the threaded ground stud right off the body.

I'm glad all is well for now!

Cheers,

Don

 

Hello and sorry for the issue... But hyper extended shocks can be caused from a weak suspension pump, abnormal front height can be caused by bent or damaged ride height sensors brackets... I have seen customers install the Arnotte shocks themselves and in a attempt to lower the arm to install they bend the height sensor clamps and the car has a small front suspension rake...usually about 2 inches too high. I suggest first inspect the suspension components, then have it tested at the dealership to see if the pump is weak...I have saw this 3 times, weak pump causing rear shocks to hyper extend... I hope this helps....

 

I too just had this happen to me. The drivers/rear tire looked like I was in an LA Low-riders event. Jacked up all the way. It felt like I was riding on a solid axle truck! With a scanner, we can see that the ride height sensor is not registering changes in height. I ordered a new sensor and it will b in next week. Meanwhile, The ABS/Check Engine, Traction control lights lit up and the power steering gets hard when I drive. All this happened when I first experienced the full airbag situation while riding down the road.

Anyone else have this same problem...and maybe a fix?
Thanks

 

I also had the rear shocks hyper extended a couple of weeks ago.. This happened after I'd had the car jacked up one side at a time to replace rear tie rod ends and sway bar links. After driving for a couple of miles in the hope that the car would recover it's composure on it's own, I went into the trunk and disconnected air lines until both ends dropped to the stops. Then I reconnected the air lines, started the engine and the car rose to it's normal height. At no time were there any malfunction warnings on the dash. Since then the ride height has been fine, but I have had "air suspension Fault" on and off on a couple of occasions. I've now purchased a Jag code reader that should be able help sort it out.

 

Hello,

I have the same problem with my suspension - rear right shock is hyper extended and is the whole back end is raised but the right side is higher. I just changed that shock a few days ago. There are solenoids in each shock to make it release air and decrease ride height. I'm wondering if that's what's malfunctioning and I'm considering changing it. Please could let me know if changing shocks fixed this for anyone? Don't want to change it out and then have the same issue again. Thanks!

 

The solenoids to add or release air are in the valve block in the trunk, not the air spring units themselves. The rear wheels each have a ride height sensor, so this may be malfunctioning, or is loose. You aren't getting a fault code because the ASM thinks all is normal. The car tries to keep itself level, so that's why the whole back end is so high. Best inspect the rear height sensors, I reckon. I'm assuming the replacement air spring unit is a Bilstein OEM, and not after-market.

 

Thanks Fraser! I checked the ride height sensors and they seem fine. I went with aftermarket shocks (may not be one of my best decisions there, but fingers crossed).

There are electrical connectors on each shock and the workshop manual says these activate solenoids. I before I replaced the shock, my car was a low rider. I found out that one of the air shocks (rear right) was leaking (hissing sound) and as a result the system sent a 12V signal to the connectors on each of the other shocks (checked with multimeter) which I presume opened an air valve within the shock to release air to lower and level the vehicle. So I pulled out the connectors on the other 3 shocks, jacked the rear right end a bit and started the car and 3 of the shocks raised up without a problem.

Now with the replacement, I have noticed that even if I completely remove the air line to the shock, it leaks a bit but holds most of the air and does not go all the way down. I am not sure if it is supposed to do that or if there is a problem with the valve and the replacement is defective. Does anyone know?

I’m also going to try replacing the compressor piston ring to see if it is due to a weak compressor as 912guy suggested. I will update on how that goes.
Thanks!

 

Hi George,

Welcome to the Jaguar Forums! It's great to have you with us.

The post at the link below will answer many of your questions about the air suspension operation:

Air Suspension & ECATS System Summary: Components & Operation

For example, the air springs have a pressure-retaining valve that prevents all of the air from escaping in the event of a leak in one of the hoses. This is to prevent the air bladder from completely collapsing and possibly being damaged.

There should never be 12 volts present at any of the damper/shock absorber electrical connectors. The Air Suspension Control Module (ASM) controls the solenoid valves that change the damping rate by sending a 5 volt 400 Hz pulse width modulated signal (a rectangular waveform) to the shocks, by which it can dynamically control the opening and closing of the valves.

The electrical connectors on the shocks only concern the ECATS adaptive damping and have nothing to do with the inflation of the air spring bladders. Inflation at each corner is controlled by the ASM via the valve block in the trunk, under the spare wheel/tire and a sound insulation cover.

Have you driven the car since you changed the air spring/shock absorber? It is possible that your system is in Jacking Mode and you just need to drive the car faster than 2 mph for the ASM to return to normal operation.

The post at the link above explains this and much more.

Also, please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don

 

Thanks a lot for your reply, Don. I have posted an introduction on the new members page. Thanks for the link.

After I changed the shock the car was good for a few days. The car was level and the ride was smooth. I drove about 80 miles over a few days, a lot of it at highway speed and the car was fine. Then the air suspension fault light came on and I also noticed the rear shocks extended. The fault light comes on a few minutes after I start driving the car. I changed the compressor piston ring and cylinder yesterday but the fault light came on as usual after a few minutes of driving today. So I guess this is not caused by a weak compressor. Thanks a lot for the leads. I'm wondering what to do next.

Thanks,
George

 

Read the fault codes ! This will give clues as to what is wrong. At least now you do have a fault indicated; it is much more difficult if there are none.

 

Yes, thanks Fraser. My scan tool couldn't read chassis codes, its just an OBD reader. I'm getting an i930 Jaguar scan tool soon (here's the link in case anyone needs it
https://www.amazon.com/dp/B00S5AB54W/ref=cm_sw_r_cp_awdb_t1_mxdZDb08GAR97 ). Will update after reading the codes.

Thanks!

 

I've got one of those sitting in my garage somewhere. It was very useful when I had a bad wheel sensor as it identified the bad part so it was a simple job to buy another sensor and swap them out. Now I have an XE with warranty, it doesn't get much use now.

 

Hope you don't have to use it again anytime soon!
I got the scan tool and the code is c2302 leveling plausibility error. I checked the tool while driving and it seems like the rear right ride height keeps extending and then the system throws the error and the ride becomes stiff. So I'm guessing the solenoid or valve in the valve block to the rear right shock might be malfunctioning. I also got a c1800 and c2779 code but I hope this might have been caused when I manually released air from rear shock to level the car because it did not come up along with the c2302 while I was driving. I think Fraser had responded to my first post saying that the valve block might be the cause - good call there! I'm going to replace it and see if it resolves the issue. Will update soon. Thanks!

 

Hi everyone,
Here's an update. I changed the valve block in the boot but it didn't solve the issue. I then changed the rear two shocks to spring and damper struts. I was hoping to keep the front air shocks to have dynamic stabilization while cornering but I changed them to springs as well eventually. I must say I am very satisfied with the springs. Not as good as the air suspension but still very good nonetheless. Sorry to give up on the air suspension - it's an awesome system but saving my energy for other problems
Thanks a lot for the help!
​​​​

 

We changed 3 out of 4 old Bilstein suspensions with new Arnott suspensions because one of the 4 new Arnott suspensions ıs not working, 2 on the rear and 1 on the front: We are waiting for replacement of the 4th non-working part. However, after changes, the front suspension drops 2 cm and the rear suspension drops 5 cm 1 hour after turning off the engine. When restarting the engine. suspension resumes to normal after 30 sec. We hope after replacing the 4th old Bilstein suspension with a new Arnott suspension on the front to complete the replacement of all 4 suspensions that the issue will be resolved. Does anyone have any experience with this type of issue?Thanks.

 

I have noticed this on my car before and my guess is that you have a small leak at one of your shocks from after the solenoid block. The entire car lowers because when the system senses a drop at one corner, it bleeds air from the other shocks to keep the car level. I would check the rear shocks first as they seem to drop lower. To find out which corner is leaking you could place a jack under one corner at a time and see if the car maintains its height - so if you place it under the rear left and the car does not drop, you probably have a leak either inside that shock or along the air line leading up to the shock from the solenoid block. Hope this helps. Good luck!