SLS disaster! Please help

Hi all, let weekend I was up in the mountains with my 2001 td5, noticed a bumpy ride, so pulled over and noticed the rear suspension was on the bump stops (both sides).

Checked fusible link & relay, both fine. Called my recovery service who came, tested the compressor and told me it's getting power but not running.

Had the car recovered home, ordered a new compressor and fitted that today. Tested the old compressor, it's fine. Checked if power was getting to the unit & it is not.

Manually overriden the relay and the compressor fires up (suggesting a Slabs error?) but although the compressor is running, the suspension will not pump up to road height. Air is getting to the airbags to fill enough air to 'shape' them with the back end jacked up, but once I lower the jack, it's sat on the bump stops....

Removed the driver side sensor, it looks nackered so I will order 2 new sensors, but that doesn't explain why both sides dropped and with the ECU over riden, the bags won't inflte...

My next plan is to order 2 new height sensors and a Nanocom incase IT has somehow put itself into transport mode (is that possible?)

Does anyone have any suggestions as to why the bags won't inflate with the Slabs ECU overriden (bridging the relay).

Thanks in advance!

Andy

Hi, you should have visited the "introduce yourself" section first... anyway, to override the SLABS and inflate the bags you have to feed the air supply valves too at the same time with the compressor otherwise the compressor pumps against closed valves so the air will not reach the bags

i attach you a pic to understand what you have to feed at the same time with the compressor then cut the feed when the car is on visually normal level and let the valves and compressor unplugged, this way if there's no leak in the system it will stay on level for many days just the self levelling will not work at least untill you properly diagnose and fix things

i hope you disconnected the battery before you unplugged the sensor cos if not you'll need a tester to erase the fault code and recalibrate heights or it will not work untill then

if the battery was disconnected make sure there's not some problem with a door switch cos the compressor will work only with a signal to BCU for all doors/taildoor closed... if you get a misslock warning when you lock with fob that could be a problem too

good luck

Thanks for your reply, you have certainly shredded some light for me!

I guess by bridging the relay and overriding the slabs ECU, I am powering the compressor but not opening the valves to let air into the bag? Although the bags do inflate to 'shape', is that possible with the ECU over ridden?

Ruined height sensors would explain why it's not self levelling and do seem a likely candidate.

I did disconnect the battery before disconnecting sensor, thanks!

Maybe a stupid question (electrics is not my strong point! If I run power direct to these valves, do I also need to Earth the connections?

Thanks again!
Andy

I dont understand what you mean by earthing the connections... those two air supply valves normally closed and they open when they get feed and must close and keep the air in the bags disconnected... read again what i said and analise the pic cos it's clear enough IMO

Yes, what you are saying makes perfect sense, I cannot explain very clearly my question though!

I will supply a direct live to the points you you have pointed out on your diagram, each solenoid has a 2 pin connector (live & earth), so I was wondering if I will have to make some kind of earth cable to each of the earth positions when supplying a live. If it doesn't run with just a live, then I will add an earth.

I suspect knackered sensors, not giving decent information to the slabs ECU therefore it's not opening the solenoids.

Thanks again!

the green line in the pic is earth(negative lead) from battery and the red one positive, that's all you need on the connectors

Hi!

Right, I connected up as per your suggestion & the air bags inflated

Took it for a short drive & it's on its arse again, so I guess the short drive when it was on the bump stops has ruined the airbags (I suspect they were 15 years old!), new airbags in the shed, so will get them on thisafternoon

One question.... After pumping up, I reconnected the blue & the White connectors and they started to deflate, I assume if they are connected with no power running to them the solenoid opens?

Thanks again!
Andy

you really should read more carefully my posts m8:

sierrafery said:

...those two air supply valves are normally closed and they open when they get feed and must close and keep the air in the bags disconnected

Click to expand...

If you drove it with valves unplugged and it dropped it means that there's a leak somewhere, probably the bags... if it dropped immediately when you plugged back the valves it means there's a problem with a sensor too, replace them as well...then if it will not work you should recalibrate the system and for that you need dedicated tester... the worst scenario is that the SLS part of the SLABS has failed cos normally if a sensor has problems you should get the SLS warning too

Thanks Sierrafery, I should read more carefully!

The bags let down slowly (both sides), assume they are fecked..... Got a new set anyway.

Ok, the sensors do seem well and truly ruined so I'll order 2 new ones tonight and a Nanocom (the amount of times this would have been useful now!!)

I thought the sensors would have no effect whilst the relay is bridged though?

Cheers!
Andy

the relay is exclusively for compressor feed and the SLABS is managing the compressor and valve feeds based on sensor inputs.... the relay/compressor has nothing to do with the valves

Ok great, that makes perfect sense as I removed sensors and found they were so corroded the threads had turned to dust & I couldn't bolt them back in!
Cheers again

Right, it's working!

Replaced both air springs & sensors today. Initially it did not work, so I directly powered the solenoids as advised before in this thread and inflated just until there was some pressure in the air bags.
Then it decided to work, so I got the wheels on and took it out for a test.

Now, the passenger side seems to be about 2cm higher.... Whether at normal height or offroad mode. If I put a digital spirit level on the roof, it reads 0 degrees, but the passenger side is always 2cm lower (I have tried parking it in different places)

Any ideas? Or should I just leave it a few days & keep measuring?

Could I have knocked the calibration out somehow? I have not disconnected the sensors whilst battery is connected.

Thanks in advance!

it needs calibration cos it lost the signal from the faulty sensor while the engine was running which is quite the same like when you unplug the sensor with battery connected if you see what i mean

I feared as much! Must say though, I find it odd that it measures 0degrees with a spirit level!

I'll book it into LR!
Cheers