Hey Everyone,

New member and X351 (2011 XJL SC) owner here, bought a bit of a project and I’m trying to sort out a non-functioning rear air suspension. Car was purchased with both amber and red ‘suspension fault, vehicle too low’ triangles illuminated. Left shock had no air in it, right shock had some air in it, compressor cycles for 2-3 seconds at start up then turns itself off. Vehicle does not run compressor or air up even after a short drive (I drove carefully on a smooth road at lower speeds so as not to stress the rear struts with no air in them - I know it’s not good for them). I tried this as I had read some people talking about the compressor not cycling until 20mph. Using an Autel MX808 scan tool I am getting the following two hard faults (there were some intermittent faults for compressor and valve block that I cleared and did not return, these faults reappear as soon as clearing them):

C1A99-10 - pressure sensor circuit
C1A33-01 - left rear corner valve

also noting that I disconnected the output line from the compressor to the valve block and the compressor will run without shutting off, makes me think the issue is in the valve block or somewhere after that?

Just wondering if anyone knows where the pressure sensor circuit is located? Is it incorporated in the valve block? Any suggestions for further diagnosis? I am trying to avoid paying someone to fix this for me, the system doesn’t seem super complicated but I couldn’t find reference to these faults directly in any of my searches here or on Google. Last issue fighting me here before I am able to drive the car so I’m hoping to get it fixed up and air in the system.

thanks guys.

 

The compressor fill up the resevoir and suspension works thru the resevoir by valve block. Resevoir is located middle of the "spare wheel" (not nessesary fitted)
I suspect the valve block. Note: Resevoir have quite a pressure, so be carefull with the pipes. By factory tool (JLR SDD) its possible run system down, up and calibrate.

 

Thanks, I was able to clear codes, run the suspension set up parameters and get the rear to air up but still only on the right side. Cleared all codes and have now only been getting the left valve block code which corresponds to the air shock that isn’t getting any air. Before I go and replace the valve block, is there any way to confirm the left air shock is issue free? I’d like to know if it will take air and hold it without leaks but of course I cannot get the system to air it up with the consistent left valve fault. If anyone has any ideas it would be much appreciated!

 

Simple: Unpressure the shocks, swap left and right pipes on valve block. Now you can test if left side rises and right not.

 



 

Yes, it happens. Sometimes you are so focus and deep on the issue that you don´t think the simpliest way. Then an random fellow drop in the site and throw an solution right "out of the box".
You might have an issue of the control signals of the valve block? It just have three solenoids controlled by PWM signal lines (Power Witdh Modulation) from air suspension module. If one signal line is cut, that solenoid do not operate. Check the wiring connector of the valve block and air suspension module in case there are moist or signs of bad connection.

 

Thanks again. All wiring appears to be fine, is there anyway to test the control module for functionality? And if I was to need a new control unit does it need to be programmed to the vehicle to function correctly? I would likely search for a good used one sharing the same part number. I am going to try a quality Arnott valve block first though and if the issue is still the same then I would have to assume it’s the control unit unless there is some way to test it definitively.

 

I've been chasing suspension problems in my XJR for months now. You don't need SDD to activate, deflate, inflate or calibrate your air suspension. You will need a scan tool but not a terribly expensive one. My Foxwell NT710 (about $300) can do all of it. The problem is if you need a module programed, the SDD is required. I bought a used Suspension Control Module off Ebay with the same part number etc hoping it would plug and play and solve my problems as my original module wasn't sending power and no luck. Instead of going down the long, expensive and painful road of getting, figuring out and employing a purchased SDD, I'm taking mine to a local shop tomorrow with the correct stuff to program the module. Far less risk and expense.

 

Yea I’ve been using my Autel MT808 for all the diagnosis which has been good. Noted on programming the ECU, I guess if it comes to replacing the control unit I’ll either need to get SDD or find someone to program it for me. I’ll get the new valve block in a couple days, will report back with the results of replacing it with an Arnott unit.

 

Quick update here, got another new valve block, installed it; same issue - still have a left valve fault. All wiring appears to be perfect without issue. It HAS to be the control module. I’m now at my limit as far as what I can do myself so I have relented and am sending it to a local shop this week, I want them to confirm my conclusion and then they can program a new control unit to the car which I can’t do with the tools I have. I’ll update here when things are resolved in case anyone needs this info in the future.

 

Did you track down the issue with the air suspension faults and get it resolved? At first glance, these error codes seem related to the pressure valve built in to the top mounting assembly of the air spring and not the valve block assembly itself.

 

Earlier up though, they said when they swapped hoses, left filled up fine so don't think it was that. Though would be good to get an update.