I see questions about the X350 air suspension system operation and faults. I would like to offer some basic information for DIYers. This is rudimentary and won’t impress the factory techs much, but the DIYers are at a pretty large disadvantage not being able to pull codes. Without codes, it is tempting to just start replacing parts, hoping for the best, but with a little deeper understanding, more logic will enter into the analysis along with actions to take. Most of what comes is strictly mechanical with no complicated electrical diagnostics other than simple stuff like relays.

The fault codes for the air suspension system are actually pretty simple and the factory techs have learned what codes point to pretty common and repetitive failures so repairs come fast, easy and accurate. Probably the most common failure in the system is the air pump itself, accompanied by its relay (R1 – Engine compartment). Fault codes C2302 or C2303 (called plausibility errors) usually point directly to the air pump. This fault simply means the air compressor no longer consistently fills the reservoir tank in a predetermined amount of time. It hardly ever means a catastrophic failure of the air pump, but it is important to consider what caused the pump to get to this state. Many related minor failures can cause the air pump failure so just replacing the pump can ignore the cause while only addressing the symptom.

First, consider how the system works – There are four air lifts, one at each wheel, fed by plastic air hoses, that come from a distribution block located in the trunk. The distribution block is supplied by an air tank in the trunk which holds a min/max amount of air that is supplied by the air compressor. This is the simple description. It gets more complicated with 4 level sensors, 2 lateral acceleration sensors, etc., but these are not the common failures so odds are on the DIYer’s side these aren’t the problem of a system fault.

The air suspension relies on both electrical and mechanical system integrity to function correctly and along with a healthy battery (important). DIYers will have to settle with the mechanical side unless they have some pretty expensive diagnostics gear. The four air shocks are expected to hold air pressure over long periods of time with very little bleed off. The plastic air lines and fittings must be air tight. The distribution block and its hoses and fittings must be air tight. The tank must be air tight and the primary line from the air compressor feeding the air tank must be air tight. Under these normal conditions, the air compressor operates within its design parameters and everything is right with the world.

If any of the system components are compromised, a small leak at any corner air shock, leaking air lines, etc., the air compressor begins to cycle more times than its designed duty cycle. As the compressor works harder and harder, it gets hotter and hotter, drawing more amps than it would under normal operating conditions. Eventually the higher amperage draw cycling in relay #1 causes the contacts to burn. When the contacts burn the relay begins to fail (always intermittently, either stuck open or stuck closed). The combination of the relay failing along with the pump performing extra duty cycles causes the fault code(s) C2302/3 which leads mostly to the air compressor replacement. Just doing this without verifying the integrity of the complete system only buys some time until the new air compressor falls prey to the same failure as the first one. I have new pumps on my self, (not rebuilt) with manufacturer warnings against replacement warranty if there are any leaks in the system.

So, although the symptoms or guessing might lead the DIYer to the air compressor, due diligence should have you inspecting all of the line connections and, at least each air shock. Make up a soap solution in a spray bottle. Before replacing any part, and with the suspension charged with air and under vehicle load, spray each plastic hose connection, look for air bubbles. If you find a leak, be careful tightening the brass compression fittings. Over tightening will cause the fitting to break or leak even more. Make small turns, 1/16th turn at a time, re-pspray. Spray the rubber boots on the air shocks at each wheel. If you see any bubbles (gulp), reach for your wallet as the shocks are expensive. If you’re sure of the system’s soundness, then drive it to see if the fault light comes back. If not, keep driving; if so, then replace BOTH the air compressor and relay #1.

BTW, if the car is sagging on any corner, you likely have a leak there, and or a bad level sensor, and the compressor is less likely to be a contributor to that problem.

Hopefully this will provide more help than it adds confusion.

 

Some sensible basic advice there - like "is it leaking" which is basic to air con checks for instance, and also about not throwing parts at the problem until these basic checks are done.

What we don't know is how the air leaks out while the car is standing and how often the compressor should operate over a journey. Anybody know what pressure the system operates at ?

 

Could any one help. I have xj8 2005 model. As soon as I turn the ignition on I get air suspension fault with out starting the engine, the ride height is correct but drives harder than normal. I have fitted new piston ring in the compressor and it seems to build up the right pressure, but the warning never goes off. If the car is left for any length of time the suspension never drops so I don't think it has any leaks in the system. Thanks phil

 

Why don't you take the car to XJK Jaguar in Newcastle-under-Lyme, just round the corner from you. They service and maintain my X350 and have all the diagnostic equipment that is essential to sorting out the air suspension. Tell them I sent you.

 

I have a 2005 Vanden Plas. I have the "air suspension fault" light on. It is intermittent. It is always off when I start it first thing. Sometimes it comes on within 10 miles of driving. Sometimes I can drive 100 miles. It always comes on though. I took it to the Jaguar dealership and they wanted to replace the reservoir and valve body. They said it was a 3 hour job when I know it is listed at .7 hours. I did not feel I could trust them. So now I thought I would consult with all of you and ask if anyone has heard of this problem the way mine is malfunctioning. I am also looking for a place to purchase aftermarket parts (when/where available).
Thanks for your input,
Jim

 

Trunk view under spare.
I have never heard of the actual reservoir going bad. The hook ups into it yes they can leak as other components can.

The reservoir, under the spare in the trunk, is very easy to get to.

 

I just soap tested the valve body and fittings in the trunk and could not see any apparent leaks. I was going to check the connections at the pump but was not able to readily find/see it. Thank you for you reply

 

Is there a lowering of any corner after the car has sat for a while?

Test the top intake on each shock for a leak before tackling the pump. It is behind the front bumper.

Also the seal area at the top of each shock.

 

I did test the connections at the two front shocks with no apparent leak. I did not find the rear shock connections yet.
Can I see the pump from under the front of the car? I would like to spray/test those connections as well.
Again, thank you for the help.

 

The fault message also throws a fault code and it is important you get these read and post them here. The most common is the air compressor piston seal starting to fail. This causes the compressor to take too long to charge the reservoir and is detected as an "air suspension fault". There are others that throw up the same fault display too.

 

You have to take the paneling out of the sides of the trunk to see the rear shock tops..

You may be able to see the pump if you take the under radiator splash guard off. Not sure.

I have only looked at it with the front bumper removed. It is on the cars lhs.

 

Got it. I will see if I can get the actual code that registered when scan was run. Thank You.

 

Hi Steve, I am new to the forum. Would you know what each coloured Dot on the air suspension XJ8 350/358 mean.
I believed there was a green and Red. Green for comfort and Red for sport. However I purchased an OSF comfort strut from eBay to
match my Green dot NSF. However the strut arrived but it is a blue spot. Any ideas please. Regards Mike

 

"I took it to the Jaguar dealership and they wanted to replace the reservoir and valve body. They said it was a 3 hour job when I know it is listed at .7 hours. I did not feel I could trust them."

Absolute crooks!!

I suggest that you have the vehicle scanned for codes.

It could be as simple as a compressor ring required.

 

Hi everyone ,I’m new(2004 XJ8)
Problem with the Air suspension, I put a new compressor,after done the installation I started the car and everything was perfect it raise,parking over night,and when I try to start it again do nothing,the compressor work normally,I try everything that I read and it is not raised back again .thanks in avance for your help

 

Have you driven, or moved the car yet?
If not drive the for car a short distance, a few feet should work.
Then the compressor should start.

 

Hi Wingrider,yes l drive around (04 xj8),the compressor star a few seconds for one minute or so after star the engine,I check for leaks and nothing ,also the levels sensor.

 

I have an XF Sportbrake 2.2 diesel 2013.
The suspension compressor is noisey and on occasion I have the fault light and information suspension error. I have bought a reconditioned compressor unit with a new relay but I am unable to find the location of the relay. Does anyone know the location.

 

Thank you for your explanation.
My situation is the following: I recently changed both of the two front air shocks, but, since the car was down (in the front), I had to change also the compressor: the car is still down for both of the front wheels.
The Jag assistance mechanic thinks that the problem is the new Aerosus compressor which is not a Wabco original and also the right new Aerosus shock is blocked.
An expert friend XJR owner suggested my to function the car with the 4 door closed (also the system doesn't work), but it didn't solved the situation, and now to change the R1 relay (eventually) replacing (just to test) with the R2 relay.
By your wide knowledge, what do you think the solution?
Thany you

 

My only issue with the air suspension is that when it is very cold (less than 20 degrees F) the front will drop overnight. If left for a few days the rear will eventually drop as well. No fault codes when started and car comes back to normal height and drive fine even in cold weather.

I was thinking it was the front air springs, but now thinking its unlikely they are both failing together and evenly (front drops to the same height on both sides over cold nights). I doubt its compressor related as the car is fine while driving and pumps up just fine when started but I could be wrong. Was debating on converting to coils but would like to keep the air is possible. Once I get into replacing the air springs I'll just convert it, but if it could be soemthing simpler I would definitely like to start there. Any input appreciated.