Disco 2 Air suspension problems

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Disco Magic

Active Member
Posts
137
Hi, I’ve got a strange fault with SLS and apologies for it being an epic.

Disco 2
7 seat
2004
59k miles.
Pair new airbags 4 years ago.

Back story, a couple of months ago I was recovered home after returning to a car park and finding it on the bump stops. I fitted 2 new ride height sensors as one was perished but reading fine and the was other showing zero voltage on Nanocom. Still no voltage with one new sensor then I identified a broken wire to the connector so I fitted a repair loom/plug. Both sensors were and still are showing voltage and output readings on Nanocom.

Drove the car for around 2000 miles with no problem until a couple of weeks ago when I unlocked it at home and opened a rear door; it dumped it’s air and dropped to bump stops. Ignition wasn’t even on.

I started the car and it wouldn’t pump up.

Nanocom didn’t show any faults, but without doing anything at all on the Nanocom, (other than fault reading - not clearing) when I started the car again it pumped straight up. However, although it stayed up the SLS button on the dash could lift it to off road height but wouldn’t lower it again to standard ride height.

I haven’t had much time so left it parked up until I could investigate.

Had a look at it over the weekend and recalibrated the ride height on level ground. SLS button working up and down so felt quite pleased and went for a short spin around the village.

Just went out to it this morning sitting nicely on air, opened the door fine, ignition on fine, started the engine and it dumped it’s air and went straight down to the bump stops.

I stopped and started the engine and it wouldn’t pump up, left it for 10 minutes and had a brew, started the engine and it pumped straight up to ride height.

All doors always closed when testing SLS operation.

I’m thinking this sounds like the SLABS ECU but would appreciate any advice how to further diagnose the problem. It’s a 7 seater so I’m not interested in a coil conversion because of type approval and insurance.

Thanks in advance for any advice.
 
Disco Magic said:
It’s a 7 seater so I’m not interested in a coil conversion because of type approval and insurance.
Click to expand...

There are threads on this, but type approval is only an issue if you live abroad and have to pass the equivalent of their MOT.
Insurance is not a problem all you have to do is tell them you have changed the suspension to springs and you can change it on your V5c, it is a totally normal modification which is totally legal.

But I'm sure you'd rather get this fixed, best of luck with it.:):):)
 
Hi, yes it can be ECU misbehaviour but it can be sticking exhaust valve too, unfortunately i dont see an easy way to rule these out other than replace. You can try something with nanocom, go in 'SLABS - outputs - SLS exhaust valve(3'rd page) and test it on/off more times while you listen how it behaves, if you hear any oddity as it doesnt make the same noise all the time or something then this can be the problem
 
Stanleysteamer said:
There are threads on this, but type approval is only an issue if you live abroad and have to pass the equivalent of their MOT.
Insurance is not a problem all you have to do is tell them you have changed the suspension to springs and you can change it on your V5c, it is a totally normal modification which is totally legal.

But I'm sure you'd rather get this fixed, best of luck with it.:):):)
Click to expand...

Thanks but, yes, I’d prefer to keep the air ride.
 
sierrafery said:
Hi, yes it can be ECU misbehaviour but it can be sticking exhaust valve too, unfortunately i dont see an easy way to rule these out other than replace. You can try something with nanocom, go in 'SLABS - outputs - SLS exhaust valve(3'rd page) and test it on/off more times while you listen how it behaves, if you hear any oddity as it doesnt make the same noise all the time or something then this can be the problem
Click to expand...

Thanks, just tried that. No audible response to SLS exhaust valve ON/OFF, have worked the buttons many times each way.

Left and right valves sound as though they’re working both ways.

If I go to SLABS utilities I can raise and lower both sides OK.

Just been down the road and back, checked the exhaust valve again with no luck and looked at faults again. I’ve had the old
23-05 SVS intermittent electrical fault 023 times. I had this a few months ago and cleared the fault with no further issues. Whilst the same ECU am I correct SLS/ABS don’t interfere with each other’s faults? I must get a new SVS and do the Option B mod.

Thanks again
 
The SVS would not affect SLS operation at all. The thing that the exhaust valve doesnt respond to the test with nanocom is suspect though, it should click like the others, if you are up to further troubleshooting you should get to the valve, unplug it then give 12V with wires directly into it's connector and if it clicks that way means it's a intermittent wiring issue between the ECU and valve or ECU fault, if no activity in the valve there's the probem

a partial check is to make sure that it's good contact in all the connectors, go to yellow C0391 and give +12v with a wire into pin 1(black/white wire) use a needle without unpluging the connector ... see if it clicks then
C0391,0377.jpg
 
I was just coming back with an update and saw your reply @sierrafery

Have been cycling exhaust valve on/off and it’s currently clicking on but much much quieter and less positive sounding than the Left and Right valves. Should it sound as loud and strong as the others?
 
Unfortunately i dont know how loud it should be cos i didnt test it myself but i presume it should be similar with the others and the fact that it didnt click first time is a sign that the problem is on that path
 
sierrafery said:
Unfortunately i dont know how loud it should be cos i didnt test it myself but i presume it should be similar with the others and the fact that it didnt click first time is a sign that the problem is on that path
Click to expand...
I think I’m going to order a new compressor.

Island 4x4 are £260 plus VAT for a compressor and £140 plus VAT for the valve block alone. Sod’s law says the 16 year old compressor will fail if I just put a valve block on it.

I do agree though, no clicking first time does point to that area.

I’ll report back...


Thanks again
 
Sorry I haven’t been back since, not been too good (not Covid).

I fitted a new Wabco compressor. First time I stopped the engine she sat down on the bump stops.

When she did stay on air I noticed a listing, down on the right side. After a few days on the bump stops then the left side followed.

I’d checked all the compressor pipes with soapy water so assumed time for airbags mine were approaching 5 years old.

Finally fitted the airbags yesterday.

Right side inflated but had a hell of a job to get the left side up. Jack up/lower nothing worked. Eventually I used Nanocom raise function and got the car sitting on air. Stopped the engine and the dreaded whoosh as the system dumped all the air again. It was dark by now so left it until this morning.

Started the car up and wouldn’t lift. Plugged Nanocom in, no faults. Unplugged Nanocom, started car and she lifted. I’d done nothing other than check faults but had seen this before that just plugging Nanocom in and removing it could make the system inflate.

Checked the airbags - left side rock solid but right side slightly soft although sitting up on air. Stopped the engine, minor air sounds. Checked airbags and ridiculously both airbags were rock solid.

Why would it inflate to full pressure after stopping the engine?

Left it sitting for a couple of hours and looked fine and airbags both still solid.

Just went out and started it again and as soon as the engine started she sat down on the bump stops again - and this was with the drivers door open.

So that’s 2 new ride height sensors, repair harness/plug to right side, new compressor and new airbags.

Could it be the SLABS ECU or is there anything else I should check first. Wits end now with 2 cars off the road

Can’t test drive the Disco as MOT expired, just pre booked test only now. At the moment I wouldn’t trust it anyway.

As always, any advice hugely appreciated.


Edit: I say no faults, there was just the intermittent SVS fault. I’ll fit a new shuttle valve switch with Option B mod sometime. Sometimes it’ll show 3 amigos sometimes not.
 
Last edited:
At this point you really should rule out the ECU and if it makes the same with a known good one then i'm affraid that it's a wiring issue and that's a nightmare to troubleshoot
 
sierrafery said:
At this point you really should rule out the ECU and if it makes the same with a known good one then i'm affraid that it's a wiring issue and that's a nightmare to troubleshoot
Click to expand...

Thanks

Stranger and stranger, went out and fiddled again and no voltage showing to right hand ride height sensor.

Left always shows 5.02v, right was something like 4.87v, I’d assumed it was a variation within tolerance.

Just now right side is 0.02v.

Looks like I should rewire the plug again unless that could also be an ECU fault.
 
Last edited:
Disco Magic said:
Thanks but, yes, I’d prefer to keep the air ride.
Click to expand...

Never used the Disco for towing until last year or two - level ride height is no issues with SLS - glad I didn't change over to springs!!! Only used for limited 4WD - serious 4WD would require springs - wouldn't want a bag to spring a leak on an isolated bush track! Only one air bag replaced since purchased new in 2003 - was going to replace airbags as a pair when one developed a small leak, but thought why create waste throwing stuff out before its time! Air compressor all good - was going to buy a refurbishment kit, but no need as yet - works perfectly; cleaned the air compressor inlet fine filter and replaced the perished coarse filter with a piece of sponge from an old car sponge! Compressor filters (two off), desiccant and compressor overhaul kits readily available on line. Only issue seems to be if one of the solenoid valves is faulty.
 
sierrafery said:
As long as the circuit is now identified better rule that out first and save target heights again after that.
Click to expand...

As there “appeared” to be voltage fluctuation when manipulating the harness to the new plug I rewired it through to the plug under the coolant expansion tank. It just felt there might be a damaged wire where it disappears into the trunking on the chassis. Far too tight to join up there hence the rewire.

Got that all done and used my second new plug but it was disastrous. The plug virtually fell to bits and even when connected there was definite voltage fluctuation just by slightly touching the plug.

I’d been dubious about the quality before that so ordered a new plug which I fitted yesterday, much better quality the second it clicked into the ride height sensor.

Once I’d connected it up the left side was showing the usual constant 5.02v and the problematic right side a constant 4.97v. With some relief I assumed this was OK.

A few mins later the right side was fluctuating around 4.5v. I switched it to a brand new backup sensor and that showed 4.97v. Decided to try the suspension but battery was flat by now so charged up last night.

First thing this morning the fitted sensor (that was 4.5v fluctuating) was constant 4.97v.

Half an hour later, without having touched or moved any plugs or wires, it was 0.02v and the ride height value had dropped (presumably due to low voltage).

I switched to the new backup sensor and it’s 0.02v too.

Left side still constant 5.02v.

I hadn’t moved, or even started, the car. Can’t believe it could be a broken wire between the connector under coolant tank and ECU as no possible movement or vibration to move it.

Sounds increasingly like the ECU. Trouble is it’s over £300 for a new one, or some old stock ones on eBay for a bit less, and the usual used ones for £15 to £40 that may or may not be in working order themselves.

I’m constantly chasing rainbows with it, is it worth another £300 gamble for a new ECU?

It had always behaved perfectly until a wire broke to the original ride height sensor plug, is it remotely possible that a damaged wire could end up frying the ECU?

Thanks again for the help.
 
sierrafery said:
So just confirm did you rewire both sensors and still erratic reading cos i didnt quite understand
Click to expand...

Sorry, the left is always constant, that’s the only reason I mentioned it.

Rewired the right side only, left side is 100% original wiring just a new sensor.

I’d just been out to it again as you were replying and the right side is now fluctuating 4.97 to 5.02v. Again, I hadn’t touched any wiring or plugs, it’s seemingly gone from 0.02 to approx 5v on it’s own since I posted about 15 mins ago. Only thing is ignition has been off but I’d turned ignition off/on during previous testing with no effect.

cheers
 
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