Recently while driving back from Las Vegas (I am assuming it occurred during this drive because it seemed fine when I was driving) I lost air in my front shocks. It did not occur while I was driving but I believe it occurred while my GF was driving because we hit some bumps (not big ones) and you could really feel them, and the ride was rough. I was thinking wow these roads are too rough or I am too hung over one of the too lol. Anyhow, the next day before I drove to work is when I noticed that the front suspension was deflated and the tires almost touching the touch of the wheel well. It is strange though to me that there are no code, warning lights ..etc. I have tried , checking the fuses, switching matching relays. I even raised the car up and removed my left tire to check out the air compressor. I did unplug the air compressor and checked for power on the plug while the car was running. I could not get any confirmation of power, but not sure that the air compressor is supposed to have power 24/7? I also did notice that there is air in the air tank under the spare tire (I cracked the tube a little bit and let some air out for a while) Anyone have any experience here, or ideas of what else I should be checking? I am pretty mechanically inclined I just don't know what the correct process should be here.

 

Do you have one or two front height sensors? Inspect that for a bent bracket or linkage arm

 

There are two height sensors left and right. They don't appear to be bent or damaged in any way. Is there some way for me to determine if anything is wrong with one of them?

 

 

The compressor shouldn't run constantly, if you really want to check it, disconnect that lead and the battery then bleed the tank partially so the compressor will be forced to run.....of course by having the connector off in that state you're going to make it throw a c2302 code most likely.

You didn't actually get the chassis codes pulled did you? I don't think height sensor failures would show a fault on the display.

Kinda stumped past that. The probability of both sensors going at the same time seems fairly low.

Wouldn't hurt to try pulling the compressor relay
bleed the shocks at the nipple on each one until they're fully deflated, then retighten
disconnect the battery for 30 seconds and replace the compressor relay while it's disconnected
reconnect battery

The sensors are just potentiometers I believe......those can have their moments of psychotic episode. I had a bit of water get into the pot of a elevator servo on an RC seaplane....freaked it out so bad it ripped the elevator off and ripped itself out of the vertical stabilizer

 

I have to say the lack of a fault code has me nonplussed. I can only suggest you go to a reputable Jaguar specialist, (if the car is undriveable, get it recovered). If this is a main agent, so be it. Any lowering of the suspension due to a leaky shock unit should cause the height sensor to detect it and a fault code be thrown, it's as simple as that.

Very puzzling !!

PS, if there are no obvious leaks, the suspension height can be reset quite easily using a lap-top with the Jaguar software to do it.

 

I do have a code reader and immediately after this had occurred I pulled the codes but there was nothing relating to the air system. Only a code related to my air intake system that sometimes comes on. I did at one point actually have the compressor disconnected and turned on the car just to see if that would throw a code and it did not throw any code or check engine light. I will try what you said bleed the front shocks at the nipples (I doubt there is much if any air in them anyhow) after pulling the relay. Are you referring to the R4 relay (I believe that is the one my book states is the air compressor) I had previously switched it with another matching one to see if it was possibly a bad relay but made no difference. Since previous post I had all ready drained all the air out of the back tank to see if I could have the compressor at least come on. Today I ran the car for about 5-10 minutes keeping an eye on the compressor and it never turned on that I could tell. Could the problem possibly be the back solenoid? Also at the moment I have the battery disconnected in hopes that if it is an electronic issue things will be reset.

 

Yeah, that's the relay.
Make sure you don't bleed the shocks with the battery off.....that will screw the calibration on the sensors up for sure.

 

At fully bled, the tires will be well into the wheel well.....to a point that any more than minor steering would cause damage

 

Well crap.. I had bled the shocks yesterday previous to seeing this post. And unfortunately my battery was disconnected when I did it : (. I have not re-connected the battery post yet. So now I have screwed up the calibration on the sensors correct. There was not a whole lot of air pressure in there at all but there was some. So that being said, now if things do get working again the height sensors will think it is at the correct height but it will actually be a little bit below where it should be, correct?

 

Yeah very puzzling to me as well. I would think if it was an issue with the pump or height sensors that some type of code or message would be thrown? But yes I think your right about to throw in the towel and send it to the mechanic. So much for saving a buck!

 

Well the good news (I think) is that it is not the air compressor. I had drained the air tank while the battery was disconnected. After inserting the air compressor relay and connecting the battery I started the car and I did hear and see the air compressor kick on and off a few times. At this point I believe it has to do with the height sensors. Are these the only things controlling the front air suspension and whether the actuator in the back turns on? Are there any relays or fuses related to the height sensors or actuator in the trunk that I can check and see if that is the issue? Brian

 

Basically yeah, the height sensors are now going to register as at correct height when they are lower than they should be.

The bad news is, still don't know WTH is going on with your car.
Good news is having the height recalibrated at a dealer shouldn't be more than 1 hour labor.

Go through your handbook and check all of the fuses that it shows as having anything to do with the air suspension.....don't think that it's a fuse as that should have triggered a fault, but it doesn't hurt to check.

Honestly, at this point, I'd hook the battery back up and see where you're sitting, literally and figuratively. If the front is still low, I think it's time to have a dealer check and calibrate.

 

Same issue on my 04 XJR no faults at all, problem was R4 relay in the trunk fuse box not providing power to Air Suspension Module hence no fault codes. That relay will require you to replace the entire fuse box but it fix the problem. Hope this helps.

 

Why would the one R4 relay require you to replace the entire fuse box?

 

Good question why?

 

Probably because Jaguar won't sell it separately. If it is removable, it will have a code number on it, and should be available from somewhere, or even be the same as another one on the car that is sold individually.

Clearly if there is no power to the ASM, it cannot send any fault signals out to the instrument module that stores and displays them. Odd that there is nothing to check the ASM is functioning, but I suppose one can go too far on checks on a car.

 

The place for R4 is not taken in the rear power distribution fuse box.
R7, which contains two SSP (Switched System Power) relays (3 and 4), that cannot be removed, triggers the ASM to startup (fuse 12).
Jaguar calls it a 'Non serviceable PCB relay'.
Fuse 12 should have been blown instead of the whole box.
If you carefully give +12V (B+) to fuse 12 for a second when the ignition is on, the ASM should start to work.
Please see the details here.

(Thanks to Reyesl we know that the air suspension relay R1 in the front power distribution fuse box supports the compressor.)