2012 LR4 Reluctant to lower from off-road suspension mode

Here's the exhaust valve opening just after ignition on:


The resulting gallery pressure (time axis is different because of the software being used)


Driving down the road this then happened to the gallery pressure at the same time that the C1A13-64 triggered:


I'm losing my mind on this one!

To continue with the saga in the hopes that this will help folks that get to follow...

This weekend I removed new AMK compressor and checked all electrical connections very carefully; this involved a continuity test on all leads while also moving them around to check for a breakage, everything checked out and all wiring harnesses look OK, here's the lead that goes to the exhaust valve and also the compressor thermometer:


A good and secure connection to the compressor exhaust solenoid valve:


I wrapped the cables to keep them safe:


I also double checked that the solenoid valve was good by measuring the following resistance (it's 16ohms) and also pulled it apart to check o'rings look OK (they do):


I installed a different reservoir valve block with a different pressure sensor to try and rule out a dodgy pressure sensor, also cleaned and double checked all connections:


So in general I went through it with a fine tooth comb and didn't discover any issues. Having completed this and put it back together I still got the C1A13-64 fault :-(. The next step is the GAP iiDTool, realizing the gravity of my situation I bought one from Island4x4 in the UK, at the current exchange rate (1.2) it was US$472, that includes £25 for shipping, it took about a week to arrive. I will pick up from there in the next post!

This evening I managed to get the GAP iiDTool connected! Bear in mind that a local shop confirmed with their scan tool that the RLM ECU is flashed for an AMK compressor I was pretty surprised to find this with the iiDTool:



Given the two compressors have different characteristics this has the potential to be a fundamental issue! Needless to say I've flashed the RLM ECU with the AMK ECU firmware and will report back in a few days if this is/was the root cause of the issue.

OK, so to close the loop on this... four days later and several trips including suspension calibration I have not once received the C1A13-64. This is great news so far... I don't want to count my chickens but so far the suspension has been rock solid.

It's been a great learning journey and I remain amazed and thankful for the help I've received here and the wealth of knowledge that exists on the internet. Thank you .

So switching the firmware to AMK sorted it in the end?

ftillier said:

So switching the firmware to AMK sorted it in the end?

Click to expand...

Yes, but the moral of the story is that not all scanners show the firmware correctly (the Indy shop had a scanner showing it as flashed with AMK firmware (incorrectly)). The iiDTool showed it as Hitachi (the iidTool being correct in this case), once flashed with AMK firmware the problems went away! I'm generally pretty thorough so I was always suspicious given I'd been through the system a few times already (so servicing valves, checking for leaks, checking wires, removing the exhaust pipe from the compressor, etc. etc. etc.).

I've left my steps if anyone gets to this point in the thread and wants to know what I did.

Hi @Longtrail - you and I must be living parallel lives. 2011 LR4 Lux 5.0L V8 non-HD w/ 105,000 miles. I got the same fault code on my first scan w/ the unit you suggested. Mine says it's intermittent and I am not having the same problems you did (yet). I also have an inclined driveway and when I get the rare error message, it's at startup. I shut it down, let it run through a system check, start it back up, and the error message is gone. No noticeable difference in the ride or other problems (so far).

Did I mention I lived in Oakland County in a small town named Lake Orion? ("Ori-on" not like the constellation.) That was about 4 years of my life during the early 2000s. Nice folks, but not "home".

Looking back, do you think you needed to service all those components or would it have worked if you simply changed out the compressor and programmed the ECU to accept it? Of course, it can only make your suspension better/more stable to have done the servicing.

My ultimate goal is to have everything work as intended. It would be satisfying, even if there were some things that I rarely or practically never use.

P.S. Regarding your comments about the camber of the wheels at different ride heights, I've noticed the suspension system seems to adjust more readily when the rig is moving. In fact, it will automatically switch to normal mode from access (and I believe off-road) whenever I am entering normal driving conditions. I was thinking maybe the compressor had more "juice" to do its job on the fly, but maybe it's the system taking this camber issue into account.

Once you go over a certain speed, the system will restore normal ride height automatically. Usually it will display a warning in the multi-function display on the instrument cluster telling you to slow down or it will return to normal height.

I've seen glimpses of this before, but this time I was looking right at it when it happened. I have an upward inclining driveway. I parked and walked around the front of the LR4 to enter the house. I heard a mechanical click and brief hiss. The front end lowered quickly, but in a controlled manner. I think it is the rig trying to level itself.

BigBriDogGuy said:

I've seen glimpses of this before, but this time I was looking right at it when it happened. I have an upward inclining driveway. I parked and walked around the front of the LR4 to enter the house. I heard a mechanical click and brief hiss. The front end lowered quickly, but in a controlled manner. I think it is the rig trying to level itself.

Click to expand...

It will self-level even with the truck off. With the truck off over night or even days, sometimes it'll self-level after opening/closing a door.