Strange Air Suspension Issue - Discovery 4 - 2010

[SpannerMonkeyUK]

Hello, please be gentle as this is my first post here!

2010 Discovery 4 TDV6.

Had a code stored relating to the right rear level sensor, so replaced, on a road test the suspension fault message came up, and the suspension crashed onto it's bump stops so looked at all the live data for the suspension and spotted the front sensor wasn't performing the same as the other 3, new sensor fitted same voltage issue, swopped left to right and the same, any ideas what I am looking for?

The data as recorded was:

	Front Left	Front Right	Rear Left	Rear Right
Access	1.53	3.23	3.23	3.23
Normal	2.03	2.50	2.50	2.50
High	2.53	1.93	1.93	1.93

 

[Blob]

What are the codes that you got? I think you might be looking too deep into the issue here. We had similar on ours a few years back, it's not the always the sensor but quite often the wiring to it, there are repair kits available for that.

As long as you are getting voltages then you're getting data. From memory, they are the are the same sensors on the same axle but working in the opposite direction, the car knows this so it will calculate accordingly so I'm surprised to see such similar readings. I'd expect 3.5 on one side to be equal to about 1.5 on the opposite assuming 5v max on the logic side (not that 0v and 5v respectively would be the limits but you get the idea).

The similarity to our issue was that I thought we had a sensor problem and after changing it the fault was much worse because I'd made the corroded wiring worse manipulating it to change the sensor.

If it were me diagnosing this fault, I'd not worry about the voltages too much but if you can read resistance on the sensors with your diagnostic that will help a bit more. Really though, I'd get the codes when the fault happens and if I'm right, you will see something along the lines of "height sensor open circuit".

Make sure you keep us updated and when you do fix it, post the resolution.

 

[SpannerMonkeyUK]

What are the codes that you got? I think you might be looking too deep into the issue here. We had similar on ours a few years back, it's not the always the sensor but quite often the wiring to it, there are repair kits available for that.

As long as you are getting voltages then you're getting data. From memory, they are the are the same sensors on the same axle but working in the opposite direction, the car knows this so it will calculate accordingly so I'm surprised to see such similar readings. I'd expect 3.5 on one side to be equal to about 1.5 on the opposite assuming 5v max on the logic side (not that 0v and 5v respectively would be the limits but you get the idea).

The similarity to our issue was that I thought we had a sensor problem and after changing it the fault was much worse because I'd made the corroded wiring worse manipulating it to change the sensor.

If it were me diagnosing this fault, I'd not worry about the voltages too much but if you can read resistance on the sensors with your diagnostic that will help a bit more. Really though, I'd get the codes when the fault happens and if I'm right, you will see something along the lines of "height sensor open circuit".

Make sure you keep us updated and when you do fix it, post the resolution.

I haven’t checked the resistance in the wiring but with three being same it made me think all four should be the same, so should it be two and two?

So the fault could still be on the right rear, the original fault location

The 5v supply is okay to the left front sensor, I checked that too… and earth is okay…

When the suspension crashes, see the attached image for the trouble codes… I can not remember the original code, only that it was the right rear sensor.

Thanks for the input so far, it’s turned into a right head scratcher, from what I thought would be an easy fix!

 

[Blob]

I'd definitely be looking at the wiring harness to the sensor. There's a couple of inches of wire from the connector plug itself that isn't taped in the loom, the plastic coating gets brittle over time and cracks then you get moisture ingress and the copper corrodes. It leads to high resistance (or at least did on ours), we could get resistance readings from live data on my friend's diagnostic (can't remember the brand, Launch perhaps? Couple of grand to buy his one).

Good that you've checked your voltages and earths but remember, you can have the volts there but that won't tell you that you have a good connection. I was surprised to find that on fitting a new sensor and then test driving it, I had more problems than I started with only to then find that one wire had completely broken off, it must have been really weak and the fitting of the new sensor was the final manipulation for the wiring connector.

There's no way I'd have refitted it like this or then driven it to see if it was ok! It lasted about 20 minutes. When I stripped the outer back to try and solder a repair into it I found the corrosion on the wiring and realised the cause of the high resistance. Ordered a repair kit for the connector and it's been spot on for almost 3 years now. I assumed that I'd be doing the others but so far they've been fine. The only correlation I had was that a while before we bought the car it had had a replacement air spring on that corner and I wonder if the fragile wiring had been damaged in the fitting of that, fractured outer wiring when it was removed and refitted then corroded over the winter perhaps? Who knows?

That's my tuppence worth on these connectors, hope you find the cause.

 

[sierrafery]

Hi, it's quite common to be a wiring/contact issue hence LR made a repair kit, google out LR030017

 

[SpannerMonkeyUK]

I'd definitely be looking at the wiring harness to the sensor. There's a couple of inches of wire from the connector plug itself that isn't taped in the loom, the plastic coating gets brittle over time and cracks then you get moisture ingress and the copper corrodes. It leads to high resistance (or at least did on ours), we could get resistance readings from live data on my friend's diagnostic (can't remember the brand, Launch perhaps? Couple of grand to buy his one).

Good that you've checked your voltages and earths but remember, you can have the volts there but that won't tell you that you have a good connection. I was surprised to find that on fitting a new sensor and then test driving it, I had more problems than I started with only to then find that one wire had completely broken off, it must have been really weak and the fitting of the new sensor was the final manipulation for the wiring connector.
View attachment 339631

There's no way I'd have refitted it like this or then driven it to see if it was ok! It lasted about 20 minutes. When I stripped the outer back to try and solder a repair into it I found the corrosion on the wiring and realised the cause of the high resistance. Ordered a repair kit for the connector and it's been spot on for almost 3 years now. I assumed that I'd be doing the others but so far they've been fine. The only correlation I had was that a while before we bought the car it had had a replacement air spring on that corner and I wonder if the fragile wiring had been damaged in the fitting of that, fractured outer wiring when it was removed and refitted then corroded over the winter perhaps? Who knows?

That's my tuppence worth on these connectors, hope you find the cause.

LR030017

Thank you for the replies, I appreciate it!

So, are we talking the wiring at the right rear sensor the orginal fault which was the start of all this, or the front left with the strange voltage issue?

I do not understand how we can have 3 sensors working exactly the same voltage wise and it not be the acting differently to the others?

 

[sierrafery]

IMO the problem is with the front left but to make sure unplug that one and see live data with it unplugged if it goes to zero or what happens cos i've seen cases when the scanner mixed up the positions

 

[SpannerMonkeyUK]

IMO the problem is with the front left but to make sure unplug that one and see live data with it unplugged if it goes to zero or what happens cos i've seen cases when the scanner mixed up the positions

I am glad you agree with me that the front left is the one misbehaving, I have checked the feedback voltage at the sensor, and checked the live data and it matches, so I am happy the scan tool hasn't got the postions mixed up.

Thanks again for the feedback, give me a few days (maximum!) and I'll report back! THANK YOU!

 

[TheMunster]

Looks like it's wired back to front or someone has fitted the wrong side sensor somehow, or fitted the right sensor very wrong!

 

[SpannerMonkeyUK]

Looks like it's wired back to front or someone has fitted the wrong side sensor somehow, or fitted the right sensor very wrong!

I would 100% agree with you, but I have had the vehicle just over a year now, and the issue only started after changing the right rear sensor!

 

[sierrafery]

If you swapped the two front sensors and the live data is the same while with front left disconencted you get zero or different reading than with sensor connected most probably the problem is on that circuit.

 

[SpannerMonkeyUK]

So, I have plugged into a friends Discovery 4, and this is what there readings were, and this one has no faults!

	Front Left	Front Right	Rear Left	Rear Right
Access	1.58	3.38	3.38	3.38
Normal	2.20	2.80	2.80	2.80
High	2.68	2.35	2.35	2.35

So I am even more confused now...

 

[sierrafery]

very strange, what kind of diag tool you have, it might have a glitch? try with FL sensor unplugged for test though are those values live readings or stored target values?

 

[SpannerMonkeyUK]

very strange, what kind of diag tool you have, it might have a glitch? try with FL sensor unplugged for test though are those values live readings or stored target values?

Snap On Zeus+

All readings where measured and not the target/expected ones...

Will unplug and see what I see... Thanks again!

 

[gstuart]

Hi

Hope u don’t mind me adding , Out of curiosity have u checked the heights that ur suspension is at first plse

Measuring in mm from the centre of each wheel to the bottom of the wheel arch liner in normal ride height, easier to place some masking tape on the centre of the wheel

It just rules out the very basic start point , plus ensuring the steering wheel angle sensor is correct

A +- 10mm allowance on each wheel is ok , This way u can eliminate that and move on if required, sometimes a re calibration can resolve issues, not always but it rules it out as u move step by step through the system

Hope that also helps u

Ps, enclosed ur screenshot the right way so easier for us to see

 

[lynall]

Ride height calibrated after new sensors fitted?

 

[SpannerMonkeyUK]

Hi

Hope u don’t mind me adding , Out of curiosity have u checked the heights that ur suspension is at first plse

Measuring in mm from the centre of each wheel to the bottom of the wheel arch liner in normal ride height, easier to place some masking tape on the centre of the wheel

It just rules out the very basic start point , plus ensuring the steering wheel angle sensor is correct

A +- 10mm allowance on each wheel is ok , This way u can eliminate that and move on if required, sometimes a re calibration can resolve issues, not always but it rules it out as u move step by step through the system

Hope that also helps u

Ps, enclosed ur screenshot the right way so easier for us to see

View attachment 339636

Thank you, for that, I posted from my phone and it wouldn't let be rotate it! Sorry!!

Front Right	Front Left	Rear Left	Rear Right
2.58v (500mm)	1.95v (490mm)	2.58 (452mm)	2.58v (464mm)

It basically all started from when the rear right sensor was replaced, so maybe I need to check the wiring and that sensor first, as based on the other Discovery I borrowed from a friend today, it seems that the front left works that way by design...