Before I anger anyone I have tried to google this and used search on many forums to find what my fault is but without success.

It's a long write up but bare with...

I have bought a cayenne which I now despise! First 2 miles of buying it, it dropped its coolant. This is all sorted by me and the help of a friend which I am very greatfull for.

The same day that I fixed the coolant pipes it's developed an air suspension issue!!

From the very beginning here is what happened... I parked up on the drive and the air compressor carried on operating which I found a little odd, I had dinner and it was still working... At this point I got very worried I started up the car and then switched it off and now it was making a huge hissing from the area where the air compressor is. It eventually cut out (maybe burnt out, I don't know).

The next day I took it apart and found that the brown line which I believe to be the exhaust line had a split in it, I cut this bit off and put it all back together. Took it out for a spin and then it aired out at the front and simply refused to go back up! I quickly ordered an air compressor rebuild kit. I left the car for around 5 days, started it up, then the front decided to raise! How? I don't know. During that time it didn't lose any air whilst stationary for a few days. Today I finally got it and I fitted the new piston ring and seal to my air compressor. Still get the same light on the dash, and now the front holds but the back decides to air out and stay like that. Extremely confused I had the car diagnosed, initially there were lots of faults I don't even remember them all but in the end we ended up with just one, 01772 - pressure sensor signal wire. It's great that I know this but still I am left baffled with what it can be.... I am extremely confused, why did just the front air out and now just the back with the front being perfect. What causes this? Is my compressor still faulty? Is it the actual big G291 sensor that the air lines connect to? Is it the ecu? Is it wiring?

Someone please help me because I do not know what to try to fix next....

I refuse to take it to Porsche because they will simply say replace the g291 and compressor = ££££

I have been to some indies and they say that it's a leak, and I feel like I am teaching them about cars! - extremely frsutrating.

Note - it occasionally allows me to select a ride level if I try it from cold in the morning. Apart from that it just sits as a random no matter which is selected.

Note 2 - when I fitted the air compressor post changing the seal and ring I watched the back raise up and then just go down again.

I hope and thinks it's some kind of sensor

 

what year is your cayenne?

 

955, 2006 reg

 

The "G291 sensor" is the air distribution block which controls where to send the air depending on inputs from the level control unit.

The "01772 - pressure sensor signal wire" indicates that either the distribution block is not getting a signal from the level control unit or vice versa. There is usually additional data after the fault code description, like "short circuit" or "open circuit" , no further description may indicate an intermittent or undefined fault.

It is unlikely that it is the compressor or the control unit as you would have had fault codes for those.

You can dig a little deeper with your diagnostic tool and check the live data on the control unit , this will give you a better idea of exactly what the problem with the signal is, or exactly which signal is the problem.

The random suspension levels are either being generated within the
distribution block (it is faulty) , or it is receiving weird instructions from the
level control unit (probably wiring fault between control unit and distribution
block)

I would start by just checking the distribution block is plugged in properly, next would be to test the distribution block.

Just my opinion.

 

Thanks a lot for the reply, how would I test the distribution block?

Just to let you know I don't have diagnostics software, it was just a local garage which diagnosed the fault codes for me. Following the 1772 code it says 'signal implausible'

Just an update: yesterday I changed the air compressor and it worked perfectly. Today I get the dreaded air suspension faulty light and the brand new compressor simply doesn't engage. Does this indicate a wiring issue? Or maybe the g291 distribution block? I did notice that I crushed my temp sensor abit when I done a rebuild on the last compressor (silly I know), could this be the cause of the issue?

Can anyone point me in the direction to find the air compressor relay on a right hand drive car? Is it under the passenger seat on the battery?

 

Yes it could be the temp sensor, this may cause the compressor not to work, as it does shut down if it overheats. There are lots of ifs and mays . You need a proper diagnostic tool to read actual values on the control unit, otherwise you are just guessing.

There is a "drive links" function on the PIWIS which will test all components.

The signal implausible is an interesting fault code because it depends on which signal is being read. It can be for instance your temperature sensor is constantly reading x degrees due to damage, but the control unit knows this value is supposed to start at x1 degrees and slowly increase to x2, Or it could be something like a pressure signal is remaining constant due to a leak, but the control unit knows the pressure should be increasing because the compressor is running,or it could also be the control unit commanding a certain valve to open, and it would expect a corresponding pressure change which it is not seeing.

The implausible signal could be from any of the modules/components attached to the level control unit (compressor, distribution block,level sensors,body sensors etc).You need to figure out which signal is implausible. This would then allow you at least to determine which wires to check or which unit to change.

 

Ok thank you for explaining. So my plan of action from here is to replace the relay for the air compressor (when I find out where it is) and I have ordered a new temp sensor. If the solution is still not found then I will take the car into a local Porsche specialist who has the correct diagnostics tools and knowledge.

 

Update:

All sorted. In my search for the relay I found a burnt out fuse located on top of the battery housing. It's the 40amp fuse, I changed it and now all works perfect. So I don't know what caused it or how long it has been like this but all my confusion and frustration is over. All works so if anyone gets an issue like mine then maybe check that fuse.

How anyone know what that fuse does because I cannot see it on any diagrams. I am still on the hunt for the relay though....

 

The 40A fuse (F13) in the current distributor on the battery is the level control compressor fuse!
http://workshop-manuals.com/porsche/...tor/page_1746/