Don B, Cambo, MoscowLeaper, please give me a hand here.

The rear of my 2006 XJ SuperV8 won't raise.

Backstory: Left the car sitting in the garage for a month and a half. The front right side collapsed. Worried about it not balancing out (since there's only one sensor in the front and it's on the left side) I just dumped the air in the whole system and figured the car would sort it out. But, it basically refused to do anything but complain about being too low. I heard the compressor and the noise of valves opening, so I know it's not totally dead.It's quite hot in Phoenix right now, so I didn't really want to spend a ton of time playing with the computer in the garage, but now I wish I had.

At that point, I hooked up the computer and started screwing around with it. I erased codes and then drove it, but no help there. I attempted to use the IDS functions to inflate/deflate/calibrate/transport-customer-modes, but nothing helped there.

Here's where I stand now:
Codes: C2780, C2302

I'm running a genuine VCM (thanks again Cambo), have a partitioned machine so I can run IDS or SDD (I hardly have used SDD, but I have it). A decent dedicated power source to keep it topped up, no worries about seeing a red battery icon.

I attempted the reset that MoscowLeaper talked about here: https://www.jaguarforums.com/forum/x...4/#post1201004
Got a failed to program message, but the front came up to regular height! The back stayed down. Trying the options to inflate rear or inflate tank fail immediately. Likely due to C2780.

I have not replaced the piston ring in the compressor, but I don't like throwing parts at things. (and like I said, it's hot out there) There was no problem when it was parked, but I suppose it could have coincidentally gone out while trying to raise the car the last time. But, it doesn't seem to have a problem raising the front.

Actually, on this last attempt, I heard a suspicious hiss from the back that I haven't heard before. I wonder if I blew a bladder in one of the rear shocks when I let the air out and it settled down farther than it wanted to. Ugh.

Any advice for things to try to get the back to come up?

My advice for others: Don't let these cars sit! LOL

 

Well your C2302 is "Levelling plausibility error" with the cause a mechanical / pneumatic fault such as:
– pipe disconnected
– air leak
And the C2780 is "ASM requires configuration" with cause/instructions "Configure ASM using WDS"

It certainly sounds as if you have a major leak at the rear preventing the rear from being raised. However, I'm surprised you haven't had C2303 which also points to air leaks

 

As a follow up to close this, I bought new shocks from RMT. Put the rear shocks on (with help from a swamp cooler and dips in the pool to keep from overheating too severely, Phoenix is no joke, the garage was 130 when I started working on it)

The rear shocks were pretty easy compared to fronts that I've done with Arnotts a while back, but I did discover some shot bushings. And my tires are corded. There is no end.

Unfortunately I don't have pictures, but I do have a quick tip for anyone who is having a hard time getting the rear shocks seated properly:

As I used my floor jack on the jacking point on the frame, I wanted to put my jack stand somewhere, but there's no designated spot that I found. I used a suspension/body pickup about a foot inboard and 6 inches to the rear of the body/frame jacking point to put the jack stand. What was interesting is that one side went so smoothly, I didn't bother resting the car on that point on the other side, just kept it on the body/frame jack point. I couldn't get the second side to line up and couldn't slide the bolt in to the bottom of the shock. As soon as I realized I needed to stick my head in there and see what was going on, I decided to rest the car on that spot on the jack stand (like I should have to begin with!) and immediately the bolt slid right in (I had the top bolts on the shock snug as I was trying to get it to seat). Like magic, everything lined up.

Just an FYI for anyone struggling with the rear suspension!

 

The jacking points aren't easy to spot actually.
Here is the Jaguar document indicating jacking and lifting points.

After replacing the rear shocks, does the rear now lift up?