right2bear

I have a 2008 A8L D3 I recently purchased and am in the process of working out some bugs in it. Upon bringing it home the air suspension light would come on occasionally but when the engine was shut off and turned back on the light would go off and I assumed would just reset itself, didn't seem too much of an issue. I did purchase the Ross-Tech OBD reader and when I initially plugged it in, it read that I had a 01772 - signal from level control pressure sensor G291 implausible signal intermittent and I also had 01583 Leak in system detected priority 3 fault frequency 1 reset counter 70. I saved them and cleared them to see if they showed up again after driving it a while. I began to notice if I left the car sit in the garage for more than a day or two the back end would really be sitting much lower than the front. Most of the time if I started it up within a minute to two, the back end would raise and be no problems. After the car sat for about a week the back end was really sitting low so I started it and I heard the pump running but it shut off after about 2 minutes but the back end did not raise at all and both the amber and green suspension lights were flashing on the dash. So I plugged in the OBD scanner and it said the same thing, 01772 signal level control pressure sensor, 01583 leak in system detected, and 01400 suspension level control lower limit exceeded. I figured the lower limit was due to it sitting as low as it was in the back so I put it up on my car lift, after a lot of jacking up different points trying to get the arms to go under the car since it was sitting so low, and I started the car with a little bit of pressure off the suspension and it began to raise like normal. After the pump ran for about a minute it shut off like normal but I had a lot of the car still on the lift so I lowered the lift and the pump then came on again for about another 2 minutes and shut off and it seemed to be at the normal ride height I was used to seeing. I started taking some measurements and the back end is significantly lower than the front, by 1"+ measuring from center of wheel to fender. I tried to research to see if that was normal but can't seem to find anything. I saved the codes again and cleared them and took for a good test drive, 10+ miles. when I got back and ran the DTC's the only thing I pulled on the level control was the 01772 signal level control pressure sensor. I have not gotten the leak in system detected again so far but it could possibly come back. Looking for any kind of possibly fixes. Thought about replacing both the rear level sensors, not sure if they might be the problem. Also should I do a recalibration of the level system? I plan to try and spray everything with soapy water as soon as I can get it on the lift again. Any pointers to start would be appreciated.

Tstealth32

Many threads on this. You need to see if it's the rear left or right. Put the car into lift mode. Once there, put the car into jack mode. Turn car off. Wait. See which side lowered. Determine where the leak is coming from....top or bottom orings, strut bag, connection valve or the top bushing.

https://www.audiworld.com/forums/a8-...oblem-2942086/

right2bear

I forgot to mention it will not allow me to select jack mode. It allows me to access the drop down arrow for yes/no but as soon as I select the yes it clears the drop down selection and stays on NO

ltooz_a6_a8_q7

Read other posts I explained how the system works. Lift, the rear goes up first then front, lower, the front first then the rear.
Both front or rear struts drop, then the chances is the valve block.
Open the valve block to check of there are leaks on any lines. G291 is in the valve block.
How to get to the valve block, it's in one of my videos under my signature.
Like I said, if you pick up a car with something not working, make sure you don't need it. It's never easy to fix anything in A8 D3.
Cheers,
Louis

right2bear

I guess the little bit of research I did on the jack mode not working said as long as you aren't attempting to lift one wheel at a time it didn't matter. When I use my car lift the entire car is getting lifted simultaneously so the air system is not trying to correct anything but I don't know why my jack mode will not work at all. Ever since I brought it home it does not work. It will let me enable tow mode but jack mode won't let me at all. Is there a fuse or something for each mode that might be the reason it won't allow me to enable it?

ltooz_a6_a8_q7

Did you put it to lift first then jack mode would work.

right2bear

Yes, I always put it into lift mode prior to using my car lift as any other position on the suspension has the car sitting too low in order to get my left arms under the car. But yes I tried every different suspension mode and tried the jack mode in each one and no matter how I do it, the car will not let me enable jack mode. Like I said tow mode does work but jack mode consistently every time (approximately 20 times of trying) always goes back to NO when I am trying to enable it. Anyone ever had this same problem. I even contacted our nearest AUDI dealer, 250 miles away, all they said was bring it in of course and they will look at it, more like start replacing parts until its fixed is my fear, $5k+ later.

MP4.2+6.0

Answer 1:

1. Bad apparent rear strut. It isn't going to get better with time. Might be other things like valve block, but 90% of time it seems to be a strut at the end (and corner) dropping the most and first.

Logical Conclusion 2:

1. You are frying your compressor, a day at a time. Not getting any better with time, but rather worse. Just double the price of #1 if (when) you fry the compressor too. Literally another 5 C bills +, or you can start trying your small motor rebuild skills.

Guess 3:

3. You might have a failing compressor relay, resulting in some of the lift mode struggles. Contributing factor is the plainly overworked compressor. Routine and Audi SOP to replace relay with failed compressor. Hassle to get at, but parts cost is only in $30 type range IIRC. Not a sure fire guess, but promptly dealing with #1 and likely #3 is your most likely tried and true bet to both getting back to a nice ride and avoiding more pain with #2.

right2bear

I was thinking the same things. I think I will order a new relay and replace it first and check for leaking struts, most likely the drivers rear since it is the first to lower upon sitting for a while. The relay is under the dash correct? What is the best relay to get, one video I watched he had a different number of relay but it was still the 40amp 12 volt relay just want to make sure I get the correct one for it that will hopefully last. Also I think I will recalibrate the level control as I just don't think the rear should be an inch lower than the front sitting on level ground in luxury position. I guess I haven't tried dynamic mode to see what ride height is but I leave it in comfort all the time anyways.

right2bear

I just read another thread of some people talking about oiling the air system that helped the valve block and air compressor, they took off the air intake hose and put a few drops of air tool oil and let it go to work. Is this a good idea, to me it makes sense and it's worth a try but wanted to see if anyone else has ever tried this with any luck or possibly worse case it takes out the compressor or something stupid. Can't imagine it would as it's not like I would dump an entire bottle in but lube seems to help any moving parts and an compressor is no different. Where would I find the intake hose to do this on a 08 A8L is it on the compressor itself or is it routed somewhere else for possibly cleaner/dryer air. Also the only video I saw on the valve block showed it was behind the drivers front wheel opposite of the compressor but on the same wheel well. The guy talked about it being vacuum hoses though which they should be air lines going to each individual air shock correct?