What does it mean if one of your height sensor is reading 42.0v and the other around in around 2 to 3 volts. Air suspension keeps failing?

this is from the WM, dont mean much to me but it might help you,

Height sensor operating voltages:

Supply voltage .. 5 volts - supplied by air suspension control module
Output voltage .. Left-hand and right-hand rear: Voltage decreases with compression and
increases with rebound Left-hand and right-hand front: Voltage increases with
compression and decreases with rebound

 ... - .- -.




Y. O. L. O.
.

Thanks, So if the front left has very high voltages does that mean the rear right has to much compression which is causing the hole system to crash, Because the rear right is sitting very high, And its height sensor was changed only the other day after it broke and bracket which it is placed onto might be in a slightly different place than what it should cause the old one was extremely hard to get off. Would it need calibrated do you think?

Hey Ive got exactly the same issue on my RR2003 except all the wheel heights are ok..
ive turnrd my brain inside out trying to figure it out, im sure one of the long time members must have come across this particular fault, if so id be really grateful if they could give us their insight please!

Things that i have already checked before finding this crazy high voltage on the nearside ( left) front

Starts up and runs all day without any fault ( on All Comms)
but as soon as i drive out within half a mile or less up comes Suspension Inoperative ( or whatever)
follow closely by th3 enevitable no Abs and DSC lights.

Faults recorded at that point are:

Instrument panel bus can + occasionally EVB function fault from ABS ( but abs ..no DCs)

i have replaced the ABS module ECU..
i have replaced all 4 height sensors
EAS ECU inplausable voltage validation ( or similar..)
have checked the speed sensonsor for all 4 wheels in live Data.. whilst driving all work consistantly and was no jumps etc..
Right height ( overall) invalid input on live data page.. ( which i think refers to the crazy volts on FNS height sensor, all the other sensors are in and around 2 volts.
Car is not sagging level wise an& holds it height all around over all the time ive had the problem..
have re de flated re calibrated the all around heights several times and seems ok

i have most recently checked the connections replaced the feed cable to the highlighted sensor.
and @dded a fu4ther earth .. thinking that the high voltage was a floating earth but no luck..
i notice with the FNS sensor plug disconnected that the volts on the plug are just .12 v
tried yet @nother new sensor .. same high voltage.. have disconnected the arm from the sensor to the chasis and rotated it to see if in some position i could get the voltage down to the typical but the best i got was around 9 volts and that would be in a position that would be unplausable what ever way around i fitted the sensor..

in desperation i have ordered a replacement EAS ECU but cant think it would be this because unplugged the volts a just .12volts as said previously..
After this i am @bsolutely stumped.. i guess i could replace the 3 wires from the sensor right back to the ECU but dont like doing this because of the mess of splicing into the 3 wires coming away from the ECU..

Im completely at a loss as to what to do next.... HELP Please..Please!
Th@nks Matt...

I would think you have a faulty reading as the battery is only 13V & there's not likely to be any transformers in the circuit to raise the voltage.
I think 5volts is the typical max voltage used by most of the sensors in a car, sometimes 10, but always below 12 so low battery voltage is less likely to cause problems / errors. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

If there is more than 5V between the supply and earth wires at the sensor plug then either the suspension ecu is faulty or another source of power is getting into the wiring from damaged wiring.

The voltage between the sense wire and the earth wire at a disconnected plug will be close to 0V.

Hey guys thanks for taking the time to reason this out for me..
As said logically there should only be low voltage at the end of the sensor lead, and in fact when unplugged this is the case..
that why i hav3 ordered a replacement ECU.. thanks.

i think in the meantime i will just check though accross the 3 sensor wires themselves.
i have checked the live data voltage reader on my Discovery 3 which essentially is the same as my RR and the sensor sensor reads fine around 2 volts....

its therefore logical to think that maybe one of the 3 wires from the sensor going back to the ECU is perhaps picking up some kind of oscillation from inside the ECU..

once i get the replacement ECU i will need to code it to my vehicle.. im not sure My All comms plug in will do this..

But sincere thanks for the kind suggestions i have received. i hope at some point tobe able to nail this down and
get this on the site for any one else who is struggling with this issue....

Thankyou.

Cheers Matt..

The 5V and sense wires could be removed from the plug at the ecu to allow testing of the voltage on the 5V and sense pins from the ecu and on the 2 wires going to the sensor. The wires are quite easily removed from the plug once the main centre section is removed from the outer housing. The main centre section can be temporarily refitted to the ecu without the outer housing to allow access to the ecu pins with a meter lead attached to a pin or a small, thin screw-driver.

Thanks for this Greame, ill try this today..
incidentally i have tried to replace the ECU but i should have realised it needs to be coded so foget this for the time being!
but with the new ECU in i notice the high volts are still there so probably ECU is not the cause...

Thankyou, Steve

Try just unplugging the main ecu plug then check the voltage on the 5V supply and sense wires at the loom connector at the height sensor.

Thats a good idea Greame, Thanks,
means i can see if there is some other feed coming into the circuit between the ECU and Sensir ends of the cable.

ill try this in a few mins when im back home
Cheers Steve

Just to report back, .. ( sorry for my gap in commenting, i have had no internet for the past week or so)

No matter what i do the front left volts vary from around 40+volts. and the Height in mms is a minus figure
the others heights are fine except the rear right.. the volts are +/- 2 volts but the height is a minus.

I have checked wiring to the front left by splicing straight from the ECU but no difference at all.
I have tried re calibrating all heights with my All Comms but whatever i set the heights to nothing radically changes..
Heightwise The car looks roughly ok all around but just a about 200 mtr of driving and up comes inactive Sus, followed by ABS warnings etc ..

and the fault ‘Invalid articulation’ shows up on my All comms ( not surprisingly)

I feel sure that i could be the ECU but ive tried a couple of used units from Ebay but they dont function so i think i need to get a garage to fit one and re code ( All comms cant do this )

Is there a floor in my reasoning ?i dont know .. Please let met know what you think.. Please anyone!,,

What happens if you leave the left front sensor unplugged. The system works in a basic mode with only 3 sensors which is probably what its doing now but leaving the sensor unplugged will show if the articulation errors still occur or not.

Thanks Greame, i have tried this..
ii get the same air sus inactive message after a couple of hundred metres of driving.. along with the’ left front height sensor faulty’ message.

what i havent checked is if i do this and look at the ‘Live Feed’ on my diagnostic tools to see if it reports ‘Ride Height invalid’

which is what im getting at the moment....

I’ll give this a go tomorrow..

Thanks...

I'm suspecting that the LF abs signal might be getting into the height sensor signal circuit due to a wiring fault. Can you unplug the LF abs sensor and go for the short drive that would normally cause the suspension fault to see if it still occurs, possibly monitoring live values for the height sensor at the same time to see if it still gets corrupted?