2012 LR4 Reluctant to lower from off-road suspension mode

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Longtrail

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Thanks - in which case I have no idea... In the VIN, the C in your case stands for model year, so

2001 - would be 1
2005 - would be 5
2009 - would be 9
and so on up to 2010 where it switches to letters:
2010 - A
2011 - B
2012 - C
It will go up to Z in 2036. So you have a 2012!

The second letter (A) is the plant in which they're built, Solihull I guess?

1670275115531.png
 

ryanjl

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CA647588 originally with AMK (I think). First compressor was replaced at the dealer, so it's conceivable I originally had Hitachi and got switched to AMK.
 

Longtrail

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It's going to visit the ($)/dealership on Friday, is this something I could ask them to figure out? Thanks Folks.

I though I'd share the review of the Unit I think I have (I also don't have an old solenoid...):

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ryanjl

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That must be one of the more informative reviews ever left on Amazon.
 

Longtrail

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A quick update on this; for those unlucky enough to have the C1A13-64 fault (Pressure does not decrease when venting the gallery") I still haven't found the solution but wanted to document what I've tried/learned so far to get rid of this problem... Certainly adding new O-rings to the three valve blocks has helped. There's a valve block at the front, one at the rear and a reservoir middle valve just in front of the air compressor (which in the US is in front of the rear driver side tire). The gallery is a term that describes air in the pipes of the system, so when the compressor isn't running and none of the valves are open it's the air in the pipes that go from (1) the middle valve to the compressor (a short pipe); (2) the air from the middle valve to the front valve block and (3) the air from the middle valve to the rear valve block. When the vehicle is lowered valves on the front and rear valve block are opened and the valve on the compressor is opened to vent air (the valve on the middle valve block is NOT opened, this is only open when the compressor is running and is only used to help fill the reservoir tank). I also observe that when the vehicle is raised the compressor comes on, the middle valve is opened (to start using the air in the reservoir tank) and all valves (front and rear) are open to pump the vehicle up; the front and rear valves are closed when desired height is established but the compressor continues to run until about 258 psi is reached in the gallery and reservoir at which time the middle valve is closed (so that reservoir has a store of compressed air at approx. 258psi) and then the exhaust valve on the compressor is opened and the gallery pressure drops to somewhere between 20 to 40psi. It's interesting! So in essence the reservoir tank is being used like a capacitor in an electrical circuit to store energy (in this case compressed air).

One common cause of the failure appears to be the exhaust solenoid valve installed on the compressor and given my concerns with the aftermarket compressor I went ahead and bought an OEM AMK compressor from the UK; having fitted this I'm still getting the C1A13-64 fault :-(.

My next suspicion was some sort of blockage in the exhaust venting system (creating back pressure), this is the bigger of the two pipes that connects to the desiccant tank on the compressor and the pipe system and exhaust that is attached thereafter. To negate this issue I tried disconnecting this pipe from the compressor (accepting that it will be noisy) but I still get the C1A13-64 fault! So this pipe:

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At this point I took the LR4 to RoverLand in Detroit (they're really awesome) and they confirmed that the RLM (Ride Level Module) ECU is flashed for an AMK compressor and suggested I look for leaks in the pipes (which I've done and don't see any)!

I've watched numerous videos on YouTube and read tons of forums but still can't figure out what might cause this fault, perhaps the pressure sensor on the middle valve but watching it via an OBD2 tool (per previous comments on this thread) I'm not seeing it do weird things! I'm officially stumped (but learning a lot!)... If I make progress I'll report back, I'm grateful for other ideas!
 

ryanjl

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Okay, I read through my troubleshooting I went through with some suspension issues. Here is the thread:


One of the codes I was getting was the same that you are getting. Looking at that thread, I had forgotten I had an issue when I deflated the suspension (to rebuild the center valve block) where the front deflated but the rear raised to off-road height or higher:


My problem wound up being the wiring on the exhaust valve on top of the compressor got disconnected:


But read that whole thread and I posted a lot of other things I had found online.

Have you replaced your air compressor yet? Sorry if I missed it. If not, a free fix may be to drop your compressor and see if anything looks amiss on the wiring for your exhaust valve. If not (and if you don't know whether your compressor has been replaced), it may be worthwhile to just replace it. Yeah, it could be throwing money at the problem, but compressors on these are around a 80k mile maintenance item, so you would just be ahead of the game.
 

Longtrail

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Thanks for responding and yes I did just change to an OEM AMK compressor, I was really careful with all connections, treating them all to a clean, some wd40 and a blast with an air compressor! The key thing in my case is the randomness of this issue; it typically happens the most when starting the vehicle (but can also happen when driving down the road or on a highway). The cable you mention goes to the compressor temperature sensor and also the exhaust valve; it looks like a new cable in my case. I can successfully change the height of the vehicle apart from when the fault has triggered which suggests that my cable is securely connected? I'll read through your thread and see if I can glean anything! Next steps also include:

- Buy an IID Tool and reflash the RLM ECU (just in case, I read this worked for somebody on another forum)
- I read other posts suggesting a link between this issue and the ride height sensors; so the vehicle doesn't move quickly enough (this ones a stretch but I will look at the sensors)
- Possibly replace the center valve and air pressure sensor (or just the pressure sensor)

Bear in mind that this fault hasn't changed since fitting this new compressor suggesting it's another issue somewhere on the vehicle...
 

Longtrail

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Just another piece of information... I notice that the fault often occurs first thing in the morning which has me thinking about cold weather (it's 28F/-2C right now). I read somewhere that just before the compressor is about to run the RLM ECU will vent the gallery pressure to reduce the start up load on the compressor?

This happened yesterday morning (like many mornings), so I get the beep and the fault but the compressor didn't run; could this be because the fault was just triggered? I also wonder why it would need to run the compressor first thing in the morning, is this because there's no pressure sensor on the reservoir and therefore it just does it after an elapsed period of time to determine what the reservoir pressure is, so, open the reservoir solenoid valve, read the gallery pressure (~240-260psi) and pump air if the pressure is too low? Just as a reminder, the gallery pressure and reservoir pressure differ unless the middle reservoir solenoid valve is open.
 

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