P38A Air suspension issue - one corner

stevelup · Sep 28, 2018

Hi

The rear right air spring is consistently at the wrong height being either too low or too high.

When the whole vehicle raises up or down, that corner moves along in sync with the rear left.

When using the diagnostic tool to raise or lower just that corner though, you can hear a solenoid click but nothing happens. It will neither inflate, nor deflate. The other three inflate / deflate on demand. It's hard to judge entirely accurately but the solenoid click sounds slightly different to the other three which is unscientifically pointing me in that direction. I'm in fact wondering if what I'm hearing is the sound of only one solenoid clicking instead of two. So the inlet / exhaust one is operating but not the one for that corner. Would fit the symptoms.

What I don't understand is why that corner can move along with the others, but not on its own. Seems weird.

Any ideas?

Cheers,

Steve

Datatek · Sep 28, 2018

stevelup said:
Hi

The rear right air spring is consistently at the wrong height being either too low or too high.

When the whole vehicle raises up or down, that corner moves along in sync with the rear left.

When using the diagnostic tool to raise or lower just that corner though, you can hear a solenoid click but nothing happens. It will neither inflate, nor deflate. The other three inflate / deflate on demand. It's hard to judge entirely accurately but the solenoid click sounds slightly different to the other three which is unscientifically pointing me in that direction. I'm in fact wondering if what I'm hearing is the sound of only one solenoid clicking instead of two. So the inlet / exhaust one is operating but not the one for that corner. Would fit the symptoms.

What I don't understand is why that corner can move along with the others, but not on its own. Seems weird.

Any ideas?

Cheers,

Steve

That corner will appear to move due to weight transfer when the whole vehicle lifts or drops.
You need to check the height sensor.
If you have the RSW EAS software, you can read and adjust individual corners, look and see what the sensor reading is for the corner that is giving trouble.
Unusual to have solenoid failure, but problems with the connectors in the EAS box are common. Pull all the connectors apart and look for signs of corrosion.
Does the EAS go into fault mode and if it does what fault is recorded?

stevelup · Sep 29, 2018

Morning!

I'm not doubting what you say about weight transfer but the range of movement is huge. With it in access mode, that corner is just off the bump stop. In 'normal' mode, it's actually higher than the other three corners. Pretty curious... and I'm not sure it can wholly be explained by weight transfer.

I've disconnected the physical link and exercised the height sensor and the range of values returned using the RSW software is broadly the same as the left hand side - nothing jumps out. I was considering swapping the left and right ones but not sure there's any point after this test.

But would a faulty sensor stop that corner from moving using the manual 'up and down' buttons in the RSW software? As I mentioned, I can hear clicking but nothing happens.

There are no error codes since I last reset it about two weeks ago. When it does go into error mode, there are loads of conflicting messages and I can't see the wood for the trees.

I'll check all the connections as you suggest as a next step. I have a spare driver module and complete set of solenoids too. I am tempted to swap that solenoid - shame it's on the bottom!

Saint.V8 · Sep 29, 2018

Conflicting error codes, shows poor diagnostic communications.

Datatek · Sep 29, 2018

stevelup said:
Morning!

I'm not doubting what you say about weight transfer but the range of movement is huge. With it in access mode, that corner is just off the bump stop. In 'normal' mode, it's actually higher than the other three corners. Pretty curious... and I'm not sure it can wholly be explained by weight transfer.

I've disconnected the physical link and exercised the height sensor and the range of values returned using the RSW software is broadly the same as the left hand side - nothing jumps out. I was considering swapping the left and right ones but not sure there's any point after this test.

But would a faulty sensor stop that corner from moving using the manual 'up and down' buttons in the RSW software? As I mentioned, I can hear clicking but nothing happens.

There are no error codes since I last reset it about two weeks ago. When it does go into error mode, there are loads of conflicting messages and I can't see the wood for the trees.

I'll check all the connections as you suggest as a next step. I have a spare driver module and complete set of solenoids too. I am tempted to swap that solenoid - shame it's on the bottom!

Loads of conflicting fault codes means, as SV8 said, you do not have good communication with the EAS.
Solenoid failure is rare, duff connections in the EAS box are not. Driver packs fail too. But if the height sensor doesn't give the correct resistance in any given position, the system cannot correctly position the corner.
The solenoid & valve must be operational if as you say the corner goes from too low at access to too high in normal mode. I'd try swapping the sensors side to side.

P38A Air suspension issue - one corner

stevelup

Member

Datatek

Well-Known Member

stevelup

Member

Saint.V8

Dyed-in-the-wool 100% RR Junkie

Datatek

Well-Known Member

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