|
4.8 Air Suspension issues, EHC 74 code and compressor won't switch on
Hi All, I really need some help with my suspension, I've read loads of threads on this but I can't find a solution. The car is now slammed to the ground and running on the bump stops, I stopped using it as soon as this happened.
I have pulled the codes using INPA and DIS and I get the 74EHC Accumulator Pressure Remains Constant (accumulator filling requested). When I searched for this I found that the compressor might need a rebuild so I rebuilt it with the kit and no difference. I could hear the top black part of the compressor clicking like it is trying to switch on but it then immediately throws the error again. So I replaced the compressor with a new (aftermarket) unit and I am getting exactly the same thing. When I try to raise the car with INPA I can hear the top of the compressor clicking but the compressor doesn't kick in, when I try to lower the car I can hear a click from the rear of the car so it appears as though the signal is being sent but the compressor won't turn on. The first few times I could hear the compressor releasing air until now the pressure reads 0.5 and there is nothing left to release. The car was already slammed before this. There is a back story: I got the inactive warning on the dash and stupidly left it for a while, then I replaced one sensor and it turned out not to be the problem but I found that the rear sensor was seized, I bought a replacement and the found the bolt pattern was different when I went to fit the new one so I drove it for a week without the sensor, the suspension was fine. I managed to fudge the bolt pattern and assumed the sensor was the same as the loom was identical, this new sensor didn't change anything. So I bought a genuine sensor from BMW and fitted that. I was still getting an error but the rocker light was now illuminated and I could raise and lower the car with INPA (I had always been able to do this). Then one day as my wife was driving the car it slammed to the ground in one journey on all 4 corners at the same time which is when I stopped using it, this was about a week or so after the sensor was changed. Since then I have been chasing the problem as above and now don't know where to look, I am not convinced that a BMW garage will know without replacing a load of parts. Oh and there is an LPG tank in the way so I can't easily get to the battery compartment. The 2 air suspension fuses in the right rear are not connected to anything (I have 2 axle EHC) and I have checked the fuse in the glove box which is fine. I am not sure where to go with this now, I would gladly take it to a garage and sink some money but it has to be within reason and I don't know where I am going to find the expertise in SW London. Is there anywhere else I can look? Should I get the LPG tank removed temporarily to get access to the battery compartment and the control module? Could it be that? Can this be repaired or only replaced by BMW? I can see all the air lines and the loom disappear under the right boot cover, is there something under there that could have gone? I notice that the connectors to the top of the compressor (3 of them) are not connected to the power loom to the bottom of the compressor so I am guessing the top bit sends a reading somewhere which then sends power to the bottom part to switch on? I am at a real loss here and I can't use the car until the is sorted, I am not sure where to go next! |
Hi mate. Welcome to the air suspension hair pulling club!
Ok..I think you’re gonna have to get access to the pump/battery area. I found when mine started playing up that the battery state of charge was affecting the pump operation so I would start by checking the voltage at the battery in cold state ie after systems idle for at least 20 mins. If it’s under 12.45 volts then it might need charging. Mine was down to 12.20 volts and died not long after. New battery and all was good again. Then I’d check connections at the comp and check when it actually is running. I don’t use INPA as it doesn’t allow a reset of the EHCII module from what I understand. I use ISTA which allows individual strut operation on a corner by corner basis, easy resets and a live check of the sensor operation. It would probably be worth your while to see if an Indy has access to ISTA and can reset your module, and see where you go from there. |
Simple things first - what is your accumulator pressure and compressor temp readings ?
From just your info it sounds like the ECU is requesting the compressor to run but there is a wiring issue preventing it from running correctly |
Thanks guys, I have all the readings, just trying to work how best to upload them...so you will have them son!
|
|
Quote:
What is ISTA? Is that the same as DIS / GT1? I don't seem to have ISTA in my list of apps. |
Hi
ISTA is the newer version of INPA (as I understand it). I use it to remove errors and reset EHCII module which is what controls the system. It allows diagnosis and test programmes etc. I highly recommend it. From those pics the first thing that stands out is that you have the same issue I did, which is a plausibility error on your front left sensor. If you look at the voltages on all of your other sensors, you'll see that they are within a similar range, except for that one. If you use INPA, look at the Offset Values from the ECU screen. In my case the offset value was -5145 whilst the other wheels were all around 400 - 450. The sensors when operating correctly put out a voltage depending on where the arm is (ie ride height). When you are setting the ride height you are telling the system which voltage you want and it goes to that point. It has a limited range and the sensors are also prone to being knocked out of place or water ingress messing them up. This is how I found my sensor https://xoutpost.com/members/lvr-alb...3-14-08-29.jpg You can see the arm pointing down. It should be like this https://xoutpost.com/members/lvr-alb...3-14-07-50.jpg If it is in the right location I would be starting by replacing the sensor. They're pretty cheap and easy to install. Then reset the ride heights etc. If that doesn't work then I used a combo of INPA and ISTA to re-write the error in the sensor range to get it back. |
From a quick look (im at work) the reservoir pressure screams you have a leak or a dead compressor to me.
|
Quote:
Then I found the right rear sensor was seized so I replaced that, first with an aftermarket one but I found the bolt pattern was not the same as the one I removed. I fitted it anyway while the new one was on order from BMW and then I replaced the new aftermarket one with a new genuine BMW one, but this didn't clear the error - annoyingly I can't remember if I got a different error after this. At this point I was still able to adjust the suspension using the laptop. The a few weeks later the car dropped to the ground and I got the ehc74 error. The LPG tank is now out and I have bitten the bullet and booked it into a specialist on Tuesday as I am flummoxed! I will have another look this weekend but I don't really know where to look next. I will check the battery compartment and probably remove the side trim to see where the cabling and air pipe goes but I don't really know what I am looking at. Will keep you updated and will post with the diagnosis from the garage. |
Quote:
|
Quote:
Regarding where to look next, there are only three things it can be, a major leak, compressor not sealing or electronic setting. Major leak can be an air bag has popped. I was lucky and happened to be near mine when it let go so heard it happen. I replaced only the bag (not the whole strut) with some help of one of the members here. Funnily enough it was the front left which was also the one giving me the plausibility errors you're getting. I would be having a close look at the bag itself there and doing leak test, and then a close look at the connections around the compressor and check what you did is properly sealed. As you've got over 13 bar on the compressor it doesn't sound like it's the issue. In your pics you've shown pressure in the accumulator. What happens to remove it? Are you activating the struts? If there are no leaks then the next step is to address that front left reading. Have you cleared errors (delete fault memory) in the module yet? Not sure if anyone here can chime in with resetting the module on INPA? I do it with Insta when playing around. This is what I had in my ride heights. https://xoutpost.com/members/lvr-alb...8-19-06-04.jpg I had to progressively adjust that value by resetting the height on that strut only (just repeating the other values on other struts) to get it back within the range of the others and it's worked correctly ever since. |
I’m going to go with your compressor is shot. You can also reactivate the ehc2 with Inpa by clearing the errors while in that module. This will activate your switch and try to air up. I have a feeling your pressure switch in the compressor is shot or stuck.
Do you have your original compressor? Also. Reset errors and make sure you watch the compressor. See if you have a leak somewhere by it, or in it. |
Quote:
https://i37.photobucket.com/albums/e...psu2rjd4h6.jpg |
Quote:
I've dropped the car off at the garage and will report back with what they say, I hope they manage to diagnose the problem, I need my car and my wife off my back! |
So the saga continues, the garage diagnosed the problem as the fuse panel, they bypassed the panel and managed to raise the car so a new one was ordered from BMW for £86. I think they are talking about the blue fuse panel located in the boot floor by the rear seats but I will confirm.
Then the discovered that one airbag was losing pressure over time so to save the hassle I got them to replace that at around £480 all in. Now they are saying the car keeps losing its calibration settings and drops as a result. They mentioned something about a valve setting that needs to be set if the compressor is replaced (which I replaced earlier). They said it accepts the settings and the ride stays level but as soon as you drive away it loses the settings and drops again. They have now tried something different and it seems to be working (will confirm what) but the tech is not 100% sure its resolved so they are going to let it sit over the weekend and see what its like on Monday. They also said they have another X5 with the same problem so I am wondering if they are making the same mistake with the calibration on both cars? While it was there I got them to replace the expansion tank and do a full service, bill currently stands at about £1000! When they told me about the fuse panel it was a lot cheaper to fix the suspension than I was expecting so I got them to do the other bits to save me having to do them, little did I know at the time they were going to find other issues! |
Could be the ride height module. I hear those are quite expensive.
|
Quote:
|
Quote:
|
Hi, did you solve your problem?
|
|
| All times are GMT -4. The time now is 08:14 PM. |
vBulletin, Copyright 2026, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.6.0
© 2017 Xoutpost.com. All rights reserved.