Hi Folks,

I've been struggling to diagnose an intermittent amber suspension fault in my 05 LR3 SE (V8) that occasionally shows up when I drive a curvy road and (rarely) right after a cold start. Recently, I took it offroading and over the course of a few miles the amber suspension warning would come on. Twice, it also gave the red suspension warning. Each time, I was able to clear the fault with my GAP tool and proceed. Once I hit pavement, it didn't happen again during the 200+ mile ride home. The two suspension faults it threw were:

C112F-27 (Air spring valve mechanical failure - actuator is stuck open)
C1130-66 (Air spring air supply - Algorithm based failure - signal has too many transitions/events)

Other suspension details that may or may not be related to the fault:

• If not driven for several days, the suspension will have dropped close to the bump stops.
• Live values with the GAP tool show that with vehicle running, the gallery pressure increases to 220 psi, then over the course of 10-15 minutes, it steadliy drops to 195 psi, at which point the compressor motor kicks in and brings it back up. Compressor temperature is about 255 degrees when it finally reaches full height.
• Live values show that the rear raises from normal to offroad height within 15-20 seconds, while the front takes about 1 minute to reach offroad height.
• Live values of ride height sensor voltage show that they fluctuate slightly more with the front left sensor than with the others, but all of them are within 0.2V of each other and there's no odd voltage spike/drop in any of them while raising/lowering.
• Both front air struts were replaced a few years ago. I think the rears are likely original (I bought it in 2017).
• Battery voltage is around 14 when driving, and the battery is only a few months old.
• Compressor desiccator cover is the aluminum type, so cracks there are unlikely. Soapy water on the compressor, the desiccator, the connections to both of them, and the exposed parts of the reserve tank failed to show leaks with it parked in offroad height and I don't hear a hissing sound there or in the corners.

Because it drops over several days with fuse 26 in, but not with the fuse removed, I think the struts and valve blocks aren't leaking. However, clearly the gallery pressure is leaking (at least when the vehicle is running while parked) enough that the compressor has to come on frequently.

My working explanation for this all is that there is a small, undetected leak in the reserve tank/connections to it that I'm not finding (maybe it's on the top side of the tank). While offroading, the struts are having to do extra work as the rig tries to keep itself level, and with poor/dropping pressure in the tank, the compressor has to kick on too often, resulting in the faults. Before I pull the tank to look for leaks, I wanted to see if this all makes sense to those of you who have dealt with these air suspensions more than I have. If not that, what are the other possibilities? I plan to refresh the desiccant but can't see how that could explain what's going on, other than possibly contributing to the slow lifting of the front end.

Thanks for taking the time to read this, and for any ideas you may be willing to share!

Captain Sygo
Bellingham, WA

 

First code generally implies that you have a valve block acting up.
Second code implies you have a leaking strut, the transitions are saying that it has to either add or remove air far more than should be needed.

If it is dropping, strut leak or valve block leak.
That is good pressure, so the compressor performance seems decent on that end. Gallery pressure should drop, it has to or the compressor can not start up - pressure too high. The gallery is not meant to be air tight per-say and you will see that it will drop A LOT and you will heard a "compressor fart" as it dumps it right before the compressor will start. Gallery pressure of zero is even fine, the system does not care and will never ever try to maintain gallery pressure. Gallery pressure is not reservoir pressure and reservoir pressure is not monitored directly, only inferred by the system opening up the reservoir valve and then trying to reach specified pressure in specified time. Once reach, center valve block closes and the pressure reading is again only reading gallery pressure.
Rear is filled first then shortly after the front will get going. This often means the rear gets the biggest advantage or the reservoir stored air and more often that not will reach desired height. But there is not enough in the reservoir for the front too especially if on stops. So then you pretty much rely just on the compressor to raise the front. If not lifting from stops, not really an issue usually. You often get the "vehicle raising slowly" alert if this happens.
OEM struts or aftermarket, if not OEM they may be done for already.
Fuse will not really matter in your case, if you are hitting the stops then you have a leak. The fuse pull only prevents leaving. Let say you have a bad leak in passenger front. With the fuse in it will try to balance things out. It can not turn on the compressor. It can not open the reservoir. So all it can do is lower and try to keep things somewhat averaged out. With the fuse out that can not happen, so if you have a leak it will drop but usually just one end, corner. If you could monitor each bag pressure you probably have one that is much lower than the rest.

I doubt you have a tank leak if you are reaching 200psi. You could have a small one of course, one the compressor can compensate for to get the PSI that high. During off road my compressor rarely fires up unless I make a heigh change. The system is pretty good at doing math and knowing when one shut is pushed up and the other lowers that there is no need to actually inflate the one that is pushed up. The valve blocks at low speed connect both side and the system, in an obscure way, treats the struts like a solid axle. So even if a strut is hanging in the air it will generally not try to deflate it to get it to lower. It just kinda uses fancy math to figure stuff out. But if you have a leak.... then yes, the compressor will run and then you will get the second code about too many transitions.

My suspicion is a leaking strut and or leaking valve block. Need to do more work to see if you can figure out which strut is leaking down. And if a valve block is leaking back into the gallery, that could explain why gallery pressure seems to hold so high for so long. My pressure drops pretty low within a short time. It seems to depend on how good the piston seals in the cylinder.

 

Thanks for the quick reply and for clearing up some of my misunderstanding about how the system works. Your comment about the fuse matches with what I had been thinking, but I didn't see it drop more in one corner, so that led me to conclude that there isn't a leak in a strut. That said, the right front generally sits about an inch lower than the left front. Your idea of checking the bag pressures intrigues me - is there a fairly easy way to do that? I don't recall seeing that option in the GAP live values. I guess I should also try soaping up the struts and blocks, as well.Thanks again!

 

No, bag pressure is sadly not monitored. Only one pressure sensor exits and that is for the gallery, which of course is only the pipes from and to the rear valve block and from center valve block to compressor. Just that "space". So the system uses smart math to figure out if there is an issue, hence the "Algorithm based failure" because while it can not detect an actual leak, it can infer there must be one.

There is no left or right gallery. But if the vehicle is not sitting level then you need to do a suspension calibration. Unless you meant after sitting a while?

If you get creative with 6mm push connects, you can make gauge kits, etc and manually check stuff. But it can be a lot of time and work.

FYI: If you look at how air struts are designed you will notice the air bladder portion is basically not at all like a balloon. It rolls and folds onto it self and the strut moved up and down. The center part contains the absorber. So it is not anything like a bladder/bag. And what happens often is the rubber part can crack where it is folded back onto itself the most often, which is at standard height. But changes in heigh can move that crack from the fold to a new location and therefor seal it up better. So sometimes you can get a vehicle that drops at standard height, fuse out, but not at off-road height, fuse out, because the crack has been moved past the fold. Also because it is not a bladder the strut can leak at other spots, usually the very top seal at the center. This is from o-rings in side failing and then their leaks into the core of the strut.

 

Update: I set the vehicle to normal height yesterday, left the fuse in, and measured the corners. Today, the corners are at the same height they were yesterday. So apparently, if there is a leak in this system, it is a very slow and appears to only show up in specific circumstances (such as flexing of the strut when offroading). Also, having seen some photos of LR3s at their bump stops, I see that my previous assessment was an overstatement. After several days, it drops noticeably, but not to the bump stops. The drop is typically larger in front than in back.

The "actuator stuck open" error for the air spring valve that I was getting while offroading does seem to point to a valve block issue. Could that issue by itself (without a significant leak) cause the "algorithm based failure/too many events" warning? The only other thing I can think of is a bad height sensor. Is there a way to test these other than by monitoring live voltage values while raising and lowering the vehicle?

 

The leak may be in the strut rubber when folded just in the right spot. When my last strut when bad I would get faults pretty much only when off-road. One one trip I had to leave the GAP tool installed and clear the fault so I could keep going and have ability to change height. That is when I knew I had a leak, found it with soapy water and replaced with OEM struts from the UK. Oddly importing parts if a lot cheaper it seems. And yes, a bad valve block can also cause a strut leak. I am not actually sure how it knows an actuator is stuck open since there are no position monitors in the blocks, as far as I know. I think it is based on resistance or something with the solenoid. You can certainly check out the values. I never needed to for a valve block so not sure which to look at specifically.