Suspension Fault Issues

[Kevintjones]

I need help with the air suspension on my 2013 LR4 (120k miles). For the past month or so, I have been getting an amber "Suspension Error" light. It would happen about 50% of the time and the vehicle continued to ride and operate normally with or without the error. The ride height control would continue to operate all of the time. I think that I noticed that the light tended to come on more often when I had my family in the vehicle with me. I have 5 kids so we weigh it down pretty good when all of us on in it. I also noticed that the vehicle was very slow to rise to off-road height, but it would eventually get there. So, this is what I did:
1. I replaced the air compressor (the entire assembly) with a new one. This didn't change the behavior of the vehicle at all. I was still getting an amber warning light about 50% of the time. I drove the vehicle with the new compressor for about 2 weeks.
2. Next, I replaced the front valve block with a new unit. I have previously owned an LR3 and a different LR4 (along with a D2 and a P38 Range Rover) so I have done these jobs before. Once again, this didn't change the behavior of the vehicle at all. I drove the car with the new compressor and the new valve block for a week or so.
3. I went on vacation for 7 days and left the car sitting. When I got back, the vehicle was still at normal height with no observable lowering. This confirmed to me that I didn't have a leak in my airbags.

I got back in town and drove the vehicle a lot for the next few days and only had one or two suspension warnings out of 9 or 10 trips so I was thinking that maybe things were getting better. But, yesterday I had major issues. I drove the car for 50 miles without issue. When I got back in the car after an hour to drive back home, the suspension system started acting up. The first warning said to remove the vehicle from the obstacle and return to normal height. I did this and started driving home. A few miles in, the red "Suspension Fault - Do not exceed 30 MPH" light came on and the car completely lowered. I pulled over and restarted the vehicle. The vehicle never could raise much in the front end and the back would return to normal. I then got a warning that the vehicle was rising too slow and that it would continue to rise when cool. A few miles later, the red "Suspension Fault - Do not exceed 30 MPH" light would come back on. I continued this process for the entire ride home. I stopped 4 times to restart the car and drive it as far as I could before the fault would come back on.

Today, I couldn't get the vehicle to raise at all or the compressor to come back on at all. As soon as I crank the vehicle, the faults come up and nothing happens. So, I took it to a local mechanic who seemed to be pretty familiar with Land Rovers and these air suspensions. He erased all of the codes and tried it again. These are the codes I have:

1. U0421-68 - Invalid Data Received From Ride Level Control Module
2. C1A27-12 - Compressor Circuit - Circuit Short to Battery
3. C1S20-64 - Pressure Increases Too Slow When Filing Reservoir - Signal plausibility Failure

These three codes continue to come up and the compressor doesn't do anything. We reconnected the old compressor (which I still had) and it runs for a few seconds before shutting down too. His recommendation is to buy a third compressor and go from there. This doesn't seem like a good solution since both compressors seemed to be working the same previously. Neither caused the warnings to go away or get worse.

Any ideas or suggestions? Right now, the vehicles isn't really drivable because it is sitting so low. Thanks for your help.

 

[ryanjl]

Some thoughts:

Your symptoms do seem like a compressor. Did you replace the compressor with the same model? There are two: AMK and Hitachi.

Could be a height sensor. Look at the 4x4 screen on your nav. Does it look like one or more wheels are going haywire? If so, it's the height sensor on that wheel.

Could be the center valve block. It's right by the compressor. Remove it and take it apart and see if there's any gunk in it (primarily dessicant from the old compressor drier).

Did you measure the height of the vehicle before it would sit overnight? If there's a leak on one of the springs, the vehicle will auto-level itself even when it's turned off, so it may look ok to you if it's a slow enough leak. Trick there is to remove the EAS fuse when you park it to keep it from auto-levelling while it sits.

 

[Kevintjones]

Thanks for the input. Yes, I replaced the compressor with the same style. I have the AMK model.
I thought about the wheel height sensor. But, none of the lines go haywire on the 4x4 screen.
I have not done anything with the center valve block. I will take it apart and see how it looks.
Lastly, I have measured the heights at each wheel overnight. I pulled the relay and nothing had dropped overnight. I don’t think that is my problem.

 

[djkaosone]

I have this same issue and did most of the things you did, but I have the older hitachi compressor. I had 2" lift rods at the time of faults then I added the sya kit and replaced the 2" with 2.5" lift rods, which made it worst.

Anyhow, with my setup now I was able to properly calibrate the suspension by adding 0.5" to each corner. It doesn't fault as much. Only when the compressor heats up past 120*C.

So, the short version is try to recalibrate your suspension first and go from there.

 

[jlglr4]

No real experience with the air suspension yet (knock on wood), so just brainstorming with you.

I agree that it doesn’t make sense to keep replacing the pump, as long as it didn’t burn itself up and its the right model. One thing you might check or replace right off the bat is the power relay, just to eliminate that as a source of any potential problems.

The short to battery suggests you’re getting power somplace when you shouldn’t be. Seems like a bad relay might cause this, but also a worn wiring harness someplace. Here’s an example where a worn through wire in the chassis directly above the compressor assembly was apparently activating the compressor vent solenoid, which in turn caused the slow to pressurize problem:

https://www.landroverworld.org/threads/suspension-fault-c1a36-01.29216/page-3.

Otherwise, central valve block leak (or any leak between the compressor and the reservoir, including the reservoir itself) seems like a good place to start, as ryanjl mentioned above. Also, maybe the exhaust valve is venting when it shouldn’t for some other reason (e.g., bad signal from control module, or clogged exhaust line), or possibly the intake line is crushed or clogged.

 

[Kevintjones]

Thanks for brainstorming with me on this. I checked the central valve block this morning. It looked brand new with no signs of foreign material at all. I doubt that is my issue based on how it looked. In addition, I have already replaced the relay as well. It didn't change the behavior at all.
I too am wondering about a worn wire. I have look around some for signs of wear, but I haven't found anything. I'm going to keep looking.

 

[jlglr4]

When I got back in the car after an hour to drive back home, the suspension system started acting up. The first warning said to remove the vehicle from the obstacle and return to normal height. I did this and started driving home.

Curious what this was about….what did you do to satisfy the warning? I assume you were not actually on an obstacle. Was the car not already in normal height?

 

[Kevintjones]

Curious what this was about….what did you do to satisfy the warning? I assume you were not actually on an obstacle. Was the car not already in normal height?

Yes, the car was already in normal height. I was in a perfectly flat parking space. I disregarded the message and started to drive. That is when most of the bigger issues started.

 

[jlglr4]

Just trying to think about how that might aid in the diagnosis of what’s wrong. Not sure how the system detects an obstacle. I’m guessing it thinks there is an obstacle when it tries to level the car by releasing air and the height sensor doesn’t detect a corresponding change. Or maybe also when adding air and not sensing a height change. Maybe someone else here knows and can chime in.

 

[Kevintjones]

Thanks for those thoughts. I have no idea. I would love for someone to chime in. I agree that may have something to do with it. I tried a third compressor today and nothing changed. The car almost immediately says “Suspension Fault” and the terrain control goes dark and the compressor turns off. I’m going to spend more time tomorrow looking at the air reservoir and looking for wire damage. I’m running out of ideas.