SLS problem doing my head in

[Timmy]

So I've been chasing an SLS problem. Please don't tell me to change to coils, I actually changed back to SLS after the last owner converted.

I've just changed both rear air bags for brand new contitechs. I've also replumbed the whole air harness from bags to compressor. Confirmed no leaks in either bag, or either fitting on each bag with soapy water.

Car will stay inflated overnight. As soon as I unlock and open door, car will deflate to bump stops.

I've swapped the left height sensor out for another used one as I was getting some strange readings on the nanocom (015 instead of 130 where I had set it). I think it may not have been plugged in correctly.

So do people think it is height sensors or something in valve body, or even the slabs ecu?

[lewy]

Wow,this is a new one,watching with interest,I presume you can hear air being exhausted when you open the door.
Will it stay inflated if you leave it unlocked overnight.
unhook the battery for half an hour whilst it is inflated,see if it droppes when you hook the battery up,dont forget the radio code.

[Timmy]

Yep sure can!

[Barefoot Dave]

Can't think of all the options in the slabs menu, but why don't you try a factory reset? I get the impression that it may have been programmed to allow a Shorty easy access/ egress.

[Timmy]

That's a good thought.
I actually have a late model slabs ecu to go in when I convert cdl. Maybe I should just put that in now!

[lewy]

Have you told the slabs that you have put the air back in

[Timmy]

Sure have. It has been working for a few months now. Sorry, WAS working...

[gusthedog]

How old is the firmware on your nanocom? I had exactly the same issue and it turned out to be that the auto height setting wasn't being stored in the car due to issues with my nanocom's software being old. Essentially (from memory here and it was 3 years ago) when you set the height you had to select the reset to bumpstops setting rather than saving the height as the buttons had been reversed on the screen but not in the software. So choosing one actually meant selecting the opposite. Does that make sense? I found the firmware issue on one of the UK forums. Updating the nanocom sorted my issue. Might be worth checking.

[Timmy]

I have just updated to the latest (1.29 from memory). As I also had read that issue.
I swear I've read every single post on sls ever written now haha!
The confusing part for me is that it happens when opening the door, which is possibly waking up the slabs?

[Roverlord off road spares]

Tim maybe it's some how switching through to TRANSPORT MODE, this will lower to the bumpstops. You did do a lift in suspension didn't you, did you fit the level arm spacer to raise the height of the ARM on the Lever?
Cheers,
Mario

[Timmy]

Definitely no transport mode on, did check that as I had heard of ghosts turning it on lol
Yes, very good point. This is possibly in line with when I did the lift.
I have put the height sensor spacers in and recalibrated based on new height too.

[Roverlord off road spares]

Maybe your nanocom is playing up. No setting the commands.
I recall you had many attempts trying to synch the BCU and ECU and then it seemed to work.

[Timmy]

But it seems to remember the settings, and pumps back up to there when I restart the car (sometimes takes a few attempts to remove the sls warning light when at bumps). So the settings, in my opinion, have saved.
The bcu sync thing was why I upgraded the firmware haha!

[sierrafery]

So if i understood well it keeps level OK while driving and over night but goes down to bumps when you unlock and open a door then it goes back to level when you start the engine?

if it's so you should rule out a sticking exhaust valve so before you leave the car over night go to the compressor housing and unplug the exhaust valve(C0781, the black one which is alone on the compressor) and leave it so... then if it will not go down in the morning when you open the door it means we are closer to the issue

[Timmy]

Thanks for the input sierra.

Tackled it further this morning, strange issue I found was the sls warning light wasn't going out after a few ignition cycles like previously. Plugged nanocom in and left height sensor reading 000.

So I swapped out the sensor with another known working one, and still 000. This narrows down to slabs or wiring, right?

Took the slabs out and replaced with newer d2a version, programmed to air and checked height sensor. Still 000.

Told the nanocom to start pumping the left bag anyway, and eventually it started registering?

Only thing I can put it down to now is the connector, or possibly a bad ground somewhere?

I still took off the exhaust valve connector as directed, that will just confirm it's to do with signal, and not the bags or hose connections.

[Timmy]

Here are the nanocom screens showing aa reading then no reading!

[sierrafery]

Check connectors C0391, 0392 round yellow and grey near the fusebox to not have bad contacts or corrosion(disconnect the battery before you unplug them cos a fault will be logged in the SLABS which will stop it work untill it's erased... double check the mode to not be on transport cos it's important, with a good SLABS if it's a wiring issue to the sensor it should log a specific open circuit fault code, also it's compulsory to have a code logged as long as the SLS warning was on due to a fault not due to transport mode when it's on without codes and the rear goes down to the bumps... unplug a sensor and start the engine for few minutes then read the fault code, you MUST get open circuit for that sesnor...if not it means that nanocom is failing again cos it happened not once... not long ago a fellow from d2boysclub was in quite similar situation, nanocom didnt show any fault but plugged in autologic and it got the fault code, here is the link if you are registered D2BC.co.uk • Login (http://www.thed2boysclub.co.uk/viewtopic.php?f=5&t=42809&sid=61f80ba0cf79404252f07457313ab1e4)

i've copied the pic of autologic reading while nanocom shown no fault code, unfortunately it seems that it makes tricks with SLABS too not just with ACE so if you have the chance try with a hawkeye, lynx, T4 or autologic cos these are all on original testbook main dealer protocol not like nanocom cos you might work in vain relying only on nanocom in this area

[Timmy]

That's concerning, I haven't been able to read any codes at all from SLS faults! I thought it was strange, given the sls warning light was on...

I'll check the connectors you mentioned, was also thinking I'll replace the height sensor connector with another off a wreck.

Frustrating! Will have to try and find someone with a testbook equivalent!

[Timmy]

Also, just confirming sierra, the plugs are near the inside fuse box? Not the engine bay one?
At work, I don't have rave to check 😟

[Roverlord off road spares]

Tim, this may all be the reason the previous owner removed the SLS and put coils in as he was about to neck himself from frustration:o
Cheers,
mario

[Timmy]

Don't think for a moment I haven't been thinking this whole week...

[sierrafery]

Also, just confirming sierra, the plugs are near the inside fuse box? Not the engine bay one?
At work, I don't have rave to check 😟
near the engine bay fusebox

[Timmy]

Yes, very good point. This is possibly in line with when I did the lift.


Hmmm, just looking at the rave location for those two connectors...

Right above the shock tower, so maybe i stressed them or knocked them while putting the new shock in?

Keen to check it out tomorrow!

[Timmy]

So 100% an electrical issue. The car stayed at the designated ride height for 2 days while I didn't touch it. I disconnected the battery, and unplugged both connectors at the fuse box, sprayed with contact cleaner and ensured they were definitely clean and undamaged.

Went and unlocked the car just then, opened the driver's door and *ppshhhhhh* the back end sinks to the bumps! GRRRRRR!

I stupidly locked the car to go and sulk, then realised I should have got readings of the sensors. So unlocked and ignition to on, both sensors reading perfect voltage and height. WTF!

Any more ideas, or any places I can measure voltages or resistances? Only problem is getting into those pesky plugs, the sockets are tiny!

[SPROVER]

I've been reading this thread and just realised I went through a very similar thing about 2 months ago. My cousin just put new air bags in his 99 Disco and it was doing something very similar. I used my Nanocom to try and get his height level and it would keep going down. I couldn't figure it out. I had used it on his car previously and it had worked. Plus I had done it on mine when I put my lift in. And it all worked fine.

Anyway, his were sitting on the bump stops. He was on his way to Rosebud and I told him to pop in at the Land rover place in Mornington. To see if they could figure it out. And what do you know! They hooked it up to there machine and set it up for him. No problems at all. He explained to them what he had been through. And they told him that some times the Nanocom can corrupt the computer. Or something along those lines.

And now he has had no problems at all with it. And a big shout out to those guys down in Mornington. They didn't even charge him for it. Top service!
Hope this helps. Maybe try one of the Land rover specialists. Shouldn't take them more then 5 min to do.

Cheers

Chris

[sierrafery]

So 100% an electrical issue. The car stayed at the designated ride height for 2 days while I didn't touch it. I disconnected the battery, and unplugged both connectors at the fuse box, sprayed with contact cleaner and ensured they were definitely clean and undamaged.

Went and unlocked the car just then, opened the driver's door and *ppshhhhhh* the back end sinks to the bumps! GRRRRRR!

I stupidly locked the car to go and sulk, then realised I should have got readings of the sensors. So unlocked and ignition to on, both sensors reading perfect voltage and height. WTF!

Any more ideas, or any places I can measure voltages or resistances? Only problem is getting into those pesky plugs, the sockets are tiny!

When you open any door the SLS becomes active and the system tends to even up the level(even if the book sais it doesnt without ignition in real life it happens) but so it does when you turn ignition off when it might lower the end a bit after you left the vehicle...to release air it must open the two air supply valves and the exhaust valve so if when the system becomes active on door open signal it opens the two air supply valves which would not affect anything as long as the exhaust valve is closed ...what i presumed is that the exhaust valve got stuck open when you left the car but as the air supply valves were closed it didnt drop then when you opened a door the air supply valves opened too and the air goes out through the stuck open exhaust valve

the exhaust valve is connected to the compressor and maybe it closes when the compresssor starts pumping then the system is behaveing normally untill it's left over night again .... i hope i could make myself understood in my rotten english but that's the theory why i said to make the test with the unplugged exhaust valve

[MarknDeb]

Does the car go back to ride height once you start to move, if it does I wouldn't worry about it, as long as it stays up while driving you shouldn't have an issue

[Timmy]

Thanks Chris and sierra again for the replies!

Both of those theories are something that I have considered but maybe it's time to put them into action...

My thought is that somehow overnight it's losing connection (cold weather, bad connection) and doing exactly as you mentioned sierra, trying to level when the door wakes up slabs. Would explain the 000 reading even though intermittent.

Chris, I've also lost a bit of faith in the nanocom if it can't even read an sls code! I'll probably take it to a dealer or the local land rover repairer and see what they can offer for insight.

[Pedro_The_Swift]

I am no expert in SLS,, but after two cars and 8 years with it,, one thing I know is that SLS wont work with the car door open. up, down, or sideways.

[Timmy]

Yep absolutely agree Pedro! Problem is that I shouldn't expect it to drop when I open a door, so something is screwy lol

[SPROVER]

Yep absolutely agree Pedro! Problem is that I shouldn't expect it to drop when I open a door, so something is screwy lol

His one was showing no codes but doing a very similar thing to yours. Maybe take a 6 pack of beers to your local Landy guy and ask him to set it for you. [emoji2]

[Roverlord off road spares]

Yep absolutely agree Pedro! Problem is that I shouldn't expect it to drop when I open a door, so something is screwy lol

Maybe it is programmed for little people so they don't have the height to try and climb into the driver's seat.:confused:

[Timmy]

I think you're right. I'll just leave it and live with the fact that it's programmed for my wife lol

[lewy]

tape the door switches closed

[sierrafery]

tape the door switches closed

That's impossible on a D2 m8, the switches are within the latch actuators:cool:

[Timmy]

Just had a thought, I changed the slabs over and I *think* before I did the calibration it still had the same issue.
Wish I remembered more clearly!

If that's the case, it has to be sensor wiring surely?

[sierrafery]

IMO a sensor wiring(or any other wiring) issue would have affected the system all the time not just after a "sleep" ... you should rule out that sticking exhaust valve thing though...which means that if it goes down to the bumps with the valve unplugged it's certain that it's stuck open cos it must be closed without feed if you see what i mean...if it keeps level with the exhaust valve unplugged but goes down with it plugged it means that the management gives a deflation command when you open the door and that would be normal only if the input from the sensors at that particular moment is higher than for normal level

what you can do alsomid to let the cable of nanocom plugged in and the driver's window opened as to have acces to plug in nanocom and turn ignition on without opening the door and read the heights then go into inputs menu and watch the valve inputs while you open the door

IMO this problem of your's is quite complicated so it needs serious investigations

[Timmy]

The problem with that theory is that when you lock the car it does the 20mm drop feature flawlessly. If valves were getting stuck, wouldn't it go all the way down when that happens?

Also, would keeping the nanocom plugged in not allow the computer to sleep? As a side I've noticed the sls doesn't function the same when I'm in the slabs menus. It's As if the nanocom overrides the slabs normal function?

[sierrafery]

It's no problem with the theory, maybe with my english or way to put things, i didnt say about VALVES getting stuck only about the EXHAUST valve

1. the 20mm drop is stopped by the system by closing the two air supply valves so even if the exhaust valve which is on the compressor is open the air stays in the bags and if in the morning the system is trying to relevel it opens the air supply valves which would not be a problem if the exhaust valve was closed but if it's stuck opened too the air leaves the bags... please read again what i explained about how the system works.

in a nutshell:
1. inflate = air supply valves open + running compressor
2. keeping air in = air supply valves closed
3. releasing air = air supply valves open + exhaust valve open

the air supply valves can be opened by the system one at a time too if only one side needs adjustment


2. i didnt say to leave nanocom plugged only the CABLE into the diagnostic socket as to be able to plug in nanoocom at the other end without opening the door and read heights and monitor valve inpouts then cos otherwise it's hard to reach the connector above the pedal through the open window:cool:

[Timmy]

Sorry my misunderstanding! Will try that then. Also keen to get testbook fault codes.

I thought nanocom instructions said something about the cable being plugged in by itself causing the nanocom to blow up and not be warranty when plugged in like that?

[sierrafery]

I can't see why to be a difference for nanocom if it's plugged into the cable or with the cable into the OBD port cos i see no logic and i've pluigged mine in so several times without any problem but if there are instructions about that better follow them and forget about this test even though it would have been a good test... but if you have access to testbook wait untill it's plugged in maybe you get a fault code and then you are on the good track

[biggin]

Xaymaca is correct. The cable should be connected to the Nanocom before plugging the obd2 plug in. This is because the earth contact is longer on the obd2 Plug than the other contacts, so the earth connects first before all other contacts which prevents voltage spikes from damaging the Nanocom.

[Roverlord off road spares]

Xaymaca is correct. The cable should be connected to the Nanocom before plugging the obd2 plug in. This is because the earth contact is longer on the obd2 Plug than the other contacts, so the earth connects first before all other contacts which prevents voltage spikes from damaging the Nanocom.
Yes !!!!!!you can get sparks out of the nanocom plug if you plug it into the cable that is already connected to the OBD2 plug.
Cheers,
Mario

[rangieman]

Luv my coils:p

[Timmy]

Go away or I'll come over and let the air out of them 😛

[Roverlord off road spares]

Luv my coils:p
You won't luv them too much after you get hemorrhoids from sitting on them too long:D.

[Pedro_The_Swift]

or you put more than a packed lunch/six pack in the back,,,:p

[Roverlord off road spares]

or you put more than a packed lunch/six pack in the back,,,:p
People that remove airbags and fit coils just can't man up they made a mistake and tell the truth that they would prefer the coils instead:D
The ride is just like chalk and cheese.
Airbags last quite a while, it's just a consumable that will need replacing at some time.

[Timmy]

So I still haven't managed to do the exhaust valve test due to a flat battery from repeated start stops. I was charging the battery (while it was still connected - I know bad form) and I was measuring the volts it was putting into the battery.
I noticed, with key out and all doors closed, that it was dropping then going back up, then repeated. I could hear a clicking when it happened.
It was the exhaust valve cutting in and out? Not sure why it would have been doing that?

[sierrafery]

the exhaust valve alone would not affect anything as long as the air supply valves are closed... that releveling thing with ignition off was discussed fe w times i think on this forum too and there's no final conclusion on it...some of them are doing it some dont but it's not normal behaviour cos the system was built as to inflate bags only with engine running(except when SLS fob is used), IMO it can be a quite common ECU missbehaviour or the ECU gets a false engine speed signal somehow

[Timmy]

you should rule out a sticking exhaust valve so before you leave the car over night go to the compressor housing and unplug the exhaust valve(C0781, the black one which is alone on the compressor) and leave it so... then if it will not go down in the morning when you open the door it means we are closer to the issue

Just following up on this issue... Battery charged, car pumped up and left overnight with exhaust valve unplugged.

Opened car this morning, started, no saggy bum. We can count out sticky exhaust valve then I guess?

[sierrafery]

Yes, it seems that it drops on management request and in this case IMO it's a ECU missbehaviour

[Timmy]

I can't understand that swapping out the ecu still has the problem occurring though? Unless as mentioned by SPROVER, the nanocom is corrupting the ecu in some way?
Really need to get it onto a testbook. Would a hawkeye bring up the error too do you think?

[sierrafery]

Hawkeye is on the same protocol with T4 and made by the same factory so it should show you a fault if there's any... anyway if you have access at least to hawkeye v.6 and you get no fault code support the body on two jacks at normal even level, go through calibration menu, and when it asks about calibration blocks confirm.... this would rule out a nanocom misscalibration issue too

by the way what values do you get in "target heights" section with nanocom? are they equal with the actual height readings when the car is on level?

[Timmy]

Yep, apart from when the left randomly reads 000.
Otherwise they're always on par with eachother. And I can change their target height with Nanocom and it stores them.

[sierrafery]

Yep, apart from when the left randomly reads 000.
Otherwise they're always on par with eachother. And I can change their target height with Nanocom and it stores them.
then IMO better replace the left sensor and calibrate again or if the sensors are new it's a contact isuue on that circuit...did you check those plugs in the engine bay?

[Timmy]

Have already done that, remember? :p

[sierrafery]

I forgot but but now it's certain that it drops on management request so there's the issue somewhere, at least swap the sensors between them and if you'll get that 000 reading on the other side it means that the sensor is the problem and if you get the intermittent bad reading on the same side it's the circuit cos as you say the ECU was ruled out.

[gusthedog]

It's the nanocom. Take it to a dealer and get them to set the height. Bet you a 6 pack it works

[Timmy]

So plugged into a hawkeye today. Doesn't seem to be ability to calibrate on it.
It did read codes that the nanocom had no idea about, so cleared them.
The car seems to be micro managing the height at traffic lights when stationary, lowering a bit then raising then repeat.

Still need to go to dealer and calibrate now. And swap height sensor sides.

[sierrafery]

hawkeye must be upgraded to v.6 to calibrate, tell to the man with hawkeye that it's free... anyway what were the fault codes though?

[Timmy]

Both were historical.

One was the exhaust valve as I had u plugged it to drive there.

The other was left height sensor connection broken or short.

I didn't get to write down the numbers quickly enough before they got cleared lol

If I had a list I'm sure I could point them out! I'll ask if he can upgrade it lol

[sierrafery]

The code numbers are irrelevant, that left height sensor code is the gist of it IMO, there's the probem on that circuit it's niot a calibration issue as long as it gets to normal level now and then

[Timmy]

Would I have been going crazy if I was wiggling the wiring loom that goes along the chassis, and seeing the left sensor height reading go from about 140 to 160?
I don't think the compressor pumped during that time. Maybe a wire has rubbed through and is getting better connection when wiggled?

[sierrafery]

The fault code and the symptom are both pointing to a problem on that sensor's circuit, you should get hold of a known good SLS chassis loom or rebuild the wiring, they used to make tricks in the sensor's plug too

[Timmy]

That doesn't sound fun to replace the full loom! I believe it does the fuel pump and other stuff too.
Perhaps I could splice in a length of 3 core wire closer to the engine bay, being I thought I saw the wiggling down the back adjust it the reading.
Stay tuned party people!

[Timmy]

Well, at this stage the car has been functioning and drivable for the last few days *touch wood*

I'm not sure if it was clearing the codes with hawkeye (they were only historical), or a good proper wiggling of the wiring loom, but it's working.

The two sides are sitting at different heights by a bit, I'm scared to calibrate using the nanocom in case that did corrupt things!

I might still take it to a dealer, suck up the money it will cost and just get it done properly. :(

Thanks for all the input everyone has offered so far!

[CU55TM Disco]

Had u thought of bridging the signal wire from the known good sensor, across to the faulty sensor. The SLS ecu would see the same height from both sides then. And would rule out a rooted sensor.

Might be time to get busy with the multimeter/test light and the soldering iron and make some repairs.

[Timmy]

Definitely not a faulty sensor as I had swapped in a known good one.

I've know recalibrated using nanocom, so wasn't that either.

I'm confident that the wiring loom is damaged, since giving it a good wiggle it's been faultless since. I need to complete a permanent fix and put new wiring in spliced up further up the harness.

[sierrafery]

Doesnt seem a too good improvisation to me cos putting them in parallel might create a voltage drop as the sensors are working based on magnetic hall effect and the SLABS is very sensitive to the input while the sensor's output is very dependent on SLABS's internal resistance so the result could be an even level both sides(whichnis good) but lower than normal

[Timmy]

Correct me if I'm wrong, but bridging the signal I don't think would make it level either.

My thought is that the compressor will keep going until the height sensor says it's at the required height.
If the compressor is pumping into the left bag, the right will be going up only marginally so the compressor I think would actually end up blowing out the bag in some cases.

Example: Left bag inflates by 20mm, the right sensor might inherently go up 5mm and so it actually ends up inflating 4 times as much as it should?

Does that theory make sense?

[sierrafery]

Not to me

bridging the signal from one sensor to both inputs and leaving one sensor unplugged will keep the compressor running untill the SLABS gets the target height input so if you start with that with even level from the bumps both bags will get the air for the same time cos the height inputs for both sides are the same being from one sensor... corroborated with what i said before about voltage drop the level might be different than the normal cos one sensor's signal divided in two can be different than on one single circuit for the reasons i explained... better dont bother with this theory and fix the wiring issue somehow then calibrate it and IMO it will be good;)

[sierrafery]

By the way, when you jiggled the wiring did the action reached the sensor's connector too...cos most contact problems are within the connetors(as an analogy with the injector harness) that's why you can find these kits on the market: Discovery 2 SLS AIR Suspension Ride Height Sensors Harness Connector Repair KIT | eBay (http://www.ebay.com.au/itm/Discovery-2-SLS-Air-Suspension-Ride-Height-Sensors-Harness-Connector-Repair-Kit-/151466538011) (read the description) so IMO better get one and hardwire the sensor to the SLABS input then IMO you'll be fixed for good

[CU55TM Disco]

Correct me if I'm wrong, but bridging the signal I don't think would make it level either.

My thought is that the compressor will keep going until the height sensor says it's at the required height.
If the compressor is pumping into the left bag, the right will be going up only marginally so the compressor I think would actually end up blowing out the bag in some cases.

Example: Left bag inflates by 20mm, the right sensor might inherently go up 5mm and so it actually ends up inflating 4 times as much as it should?

Does that theory make sense?

Wont make it level, but will determine if it is the sensor or wiring that is causing grief.

[Timmy]

Latest update.

I replaced the plug and about 100mm of wiring on the left hand sensor. Got a really good condition plug off a wreck.

So far it seems happy! Reading a lot higher than it previously was. I soldered all the connections, heatshrinked, then electrical taped the loom back up from protection.

Have since recalibrated but needs some fine tuning - it's surprisingly hard to find a flat surface around here!

[CU55TM Disco]

Good news mate!

My left and right are within 10mm of each other, no matter how many times I recalibrated, and then fine adjusted witht the nanocomm, thats where they wanted to sit...


Latest update.

I replaced the plug and about 100mm of wiring on the left hand sensor. Got a really good condition plug off a wreck.

So far it seems happy! Reading a lot higher than it previously was. I soldered all the connections, heatshrinked, then electrical taped the loom back up from protection.

Have since recalibrated but needs some fine tuning - it's surprisingly hard to find a flat surface around here!