So I am finally getting to work my new to me 05 XJR. I bought it knowing the front right strut was bad. I have replaced the strut with a used unit and the car came up and looks to be at normal ride height. However within a few minutes of starting the car I am getting an "Air Suspension Fault" light on the dash. I am thinking that the compressor is timing out but my dilemma is that I plugged in my iCarsoft scanner to the car and tried to read the code and it comes back as "no faults" for the air suspension (huh). Not sure where to go from here.

The car only has 65k on it and is in very good condition. Should I just roll the dice and do a piston ring on the compressor?

Anyone with thoughts that might help?

 

Does it lose height when sitting for a while?

Try doing a hard reset by taking off battery leads and touching them together for a few seconds than reconnect.

 

Doesn't seem to have lost any height. Light comes on after a few minutes even while just sitting. I felt like I could actually feel the compressor cut off as the light came on while sitting still today. Just strange that the iCarsoft doesn't show any code. On my 08 XJ I would get the compressor plausibility code for a similar situation.

I've only driven the car about 50 miles since I did the strut and as it definitely feels different with the sport suspension than on my old 08 with comfort. It is hard to tell yet if it could be in the suspension itself because I am not sure how it should feel. Really did not want to go used on the strut but the budget dictated at this point.

I can reset the battery easily enough, which is new as well, so it is worth doing it regardless but I did have the battery disconnected to change out the strut.

 

Just disconnecting will not reset anything. Touch the cables while disconnected will.

You might get lucky and the compressor might be ok.

 

Roger that. Battery disconnect and touch to commence shortly.

The good new is that I had to do the compressor ring on my 08 recently so I bought another BPA kit at the same time. So even if I end up having to do that too I am well versed at the job. Not saying I will enjoy it but I can do it :-)

 

Well I disconnected the battery and touched the cables together last night. Ran the car for almost ten minutes sitting still and no light. I'm thinking great. I was hoping to transfer the registration from my old 08 XJ tomorrow and start driving it so I was feeling good. But just now at lunch I go out and start the car for a few minutes to double check one more time. Car runs fine for about 2 minutes and then not only does the suspension light come on but I also suddenly get lights for gearbox fault, park brake fault, restricted performance, no communication message on the center display, engine light and on and on.

What the heck just happened?

 

You say that the battery is new. Have you run a test on the battery to check its output?

Having all those faults come up has for many been indicative of a failing battery.

I am also wondering if you have a bad ground connection somewhere.

 

The battery is brand new and was put in this summer but the car has been sitting while I was getting the 08 sold. I do feel like it is an anomaly as I have driven the car a couple of times on a dealer plate and it has been okay other than the suspension light. I am going to pull the battery and give it a good charge and try all of this again. I will also at least service all of the grounds behind the headlights just as PM to start. I really don't feel like I should have to chase this car as it is in very nice condition overall.

Just sitting in the driver seat however I can distinctly feel the compressor abruptly cut off and then the suspension light comes on immediately. I guess the good news is that whatever is happening the system is communicating.

My 08 despite the high mileage treated me very well. I hope this one doesn't turn out to be a PITA. About to give the Governor tax money to register it.

 

How long does the pump run before cutting out? Your suggestion about rebuilding it sounds good if it is running too long and then cuts out. Can you read codes at the ODBll connector?.

Also as I am sure you are aware those grounds behind the lights are easy to break they require quite a low torque to tighten.

 

That is why I started the thread. The light comes on but I am not getting any codes when I plug into it. I recently bought an ICarsoft LR 2.0 and have used it successfully on the 08 to read the suspension codes. Funny thing is on the 05 when I go into the air suspension diagnosis, I have twice now gotten either no codes or a transmission P code under air suspension diagnosis. That totally threw me.

I actually don't feel the compressor when it starts running but it seems that after the two minute cycle time It cuts off and I can definitely feel it when it happens. I am guessing that it can't hurt to put the BPA kit in just so I am starting at a zero baseline as far as that goes. It is not that hard a job as long as the cover bolts don't break off.....yup i have done that.

And yes I will go easy on the studs up front. I did them on my 08 so I should be good to go.

Hoping to register the car tomorrow. Might just do it good to get driven if I can sort out the lights. I had tried last week and the CT DMV decided they wanted more paper to prove my wife knew I was going to add her to the title. Apparently signing the registration form isn't good enough anymore. That and she signed one paper with her middle initial and one without. I guess they want to make sure I am not married to two different women with the same first and last name but different middle names. (yes, I am annoyed)

Thanks for replying with your thoughts. it can drive you crazy trying to think it out alone.

 

I hear you! My wife has a different surname than mine. That creates a lot of confusion with some "people"!

Good luck.

 

Well the car is registered! I also charged the battery for several hours, started the car without issue, and have successfully cleared all of the trouble lights. I am finding that the iCarsoft is not a perfect tool. For some reason it claims it cant link to do a simple OBDII test. Better than not having it at this point so at least it cleared what issues I had. Unfortunately on my first ride home with the car the suspension light came on again and I also thought I heard air leaking from my new used front strut. The ride even seemed to get progressively harsher. Sure enough I can lift up on the fender and hear air leaking so I think my gamble on used parts has failed. If i shut the car off and restart it it actually seems to build pressure again until you start driving. It is disappointing and puts my desire to rebuild the compressor on hold until I can get another strut installed. Also reached out to the seller who claims they give 30 days but I'm not going to hold my breath. For now I'm happy she ran good on the way home for 20 miles.

 

Well I ended up purchasing a pair of reman struts and for now replaced the faulty right front that I had gambled on used. I am getting good at changing out front struts. I can report that the car has run flawlessly for a week now. Man I like this supercharged engine! I also performed the first oil change under my ownership which revealed a very clean machine with the shroud removed so I am happy happy. So all of the panic for lights, errors, etc did boil down to a faulty strut and a battery that needed a good charge. And I reached out to the eBay seller that I bought the used strut from who was very cooperative and at my suggestion agreed to refund half my money. A satisfying ending to this thread.

 

When you get a suspension fault, the CATS system defaults the shocks to 'Hard', so that's why you noticed the suspension hardening up. Did you check those grounds behind the headlamps They are notorious for corroding and failing to provide a path to earth. The system then tries to find another path that results in loads of faults coming up.

 

Yes grounds are good and car now rides as it should. The bad strut would leak on rebound eventually lowering the front end while I drove. I think the compressor was timing out trying to keep up and hence the warning light. I am now enjoying a supercharged XJ with no faults. My 08 was fairly quick but this definitely has some get up a go. Subtle power....nice.