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D4 Fault code interpretation **Resolved**
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Pauliebanger
 


Member Since: 23 Jun 2023
Location: Lincoln
Posts: 25

United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Loire BlueDiscovery 4
D4 Fault code interpretation **Resolved**

Hello,

My D4 2013 has a suspension fault. The vehicle is on the bump stops and will not 'inflate', though the compressor's motor does run briefly on start up if the fault code has been cleared beforehand.

This post is enquiring about how to interpret/use the fault codes revealed by the IID tool.

I have read the following fault code using my Gap IID tool:

C1131-92 – Air supply – Component failure - performance or incorrect operation (68)

I can see from the code structure at section 4.3.3 the user manual that the code and definitions agree and that a component failure has been identified. The hex code 68 indicates that the test failed since last cleared and that is it confirmed.

Since there are now no other fault codes recorded, is it reasonable to assume that the air supply unit has failed?

The LR workshop manual suggests the following action for Air supply issues ''Using the manufacturer approved diagnostic system, check for suspension air supply unit related DTCs''

Is it possible using the GAP tool to identify which specific component in the 'air supply unit' has failed? eg compressor, motor, or dryer etc?

Or is this where I need to physically inspect the air supply unit, its associated plumbing and wiring to effect a diagnosis?

Best regards,

Paul
 

Last edited by Pauliebanger on 27th Sep 2024 7:52 pm. Edited 1 time in total 
Post #237739815th Sep 2024 4:48 pm
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grzesiul
 


Member Since: 11 May 2008
Location: UK
Posts: 6398

Poland 2016 Discovery 4 3.0 SDV6 SE Auto Loire BlueDiscovery 4

looks like your compressor is kaput!

GAP nor other tool would show whether compressor motor is gone or dryer is fuked ....

Also manual indicates clearly EAS leak on massive scale or air unit faulty

good luck
Greg
  
Post #237743116th Sep 2024 6:14 am
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Pauliebanger
 


Member Since: 23 Jun 2023
Location: Lincoln
Posts: 25

United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Loire BlueDiscovery 4

Hi Greg,

Thanks for your response, I appreciate your help.

Due to a recent injury I can't do much physical work at the moment, so I'm using the down time to get as much info/evidence together as possible to try to understand what the problem is, what was the cause, how many other components may need to be checked and so on.

So these are my thoughts so far.

You are correct, the WS manual effectively indicates that either the air supply unit has failed or something else in the suspension system has failed. Which of course in isolation does not really tell me anythng I didn't already know or could have deduced.

So I just wanted to know if further scans or maybe live data could reveal more to narrow down the scope for initial investigation.

I suppose this illustrates what I was alluding to i.e. the codes will not always specifically identify the failed compnent and must be interpreted in conjuntion with other available scanned data and visual inspection/testing.

When I first read the fault codes, a second one, C1A20 - 64, was present. This indicates 'Pressure increases too slow when filling reservoir'. This could be incorrect valve opertions or air leaks before or downstram of the reservoir or a failed air supply unit.

After clearing all fault codes, only C1131-92 now reappears. This leaves my interpretation as 'air supply component failure'.

I suspect, therefore, that your 'faulty compressor' diagnosis is correct so that's where I'll start investigating. I recognise that other underlying failures could have caused the unit to fail but until I can get some pressure into the circuit there's not much pressure testing I can do.

Best regards,

Paul
  
Post #237744016th Sep 2024 9:35 am
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grzesiul
 


Member Since: 11 May 2008
Location: UK
Posts: 6398

Poland 2016 Discovery 4 3.0 SDV6 SE Auto Loire BlueDiscovery 4

sorry to hear about your health

i guess simplest thing to do would be looking for leaks in all relevant spots where valve blocks are as well as air line connections on top of the air struts and all, does not demand too much of physical hard work

on gap tool you can look at full list and tick all sections related to EAS and record output which might be as meas-leading as anything else.


your latest code clearly states the following:
Air spring or pipe air leak
Suspension air supply
unit failure

so if you have amk or hitachi unit just get one from ebay where there are plenty of good uns for like 150 quid

replacement is super simple

good luck

G
  
Post #237744416th Sep 2024 11:09 am
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Martin
Site Admin and Owner 


Member Since: 06 Nov 2004
Location: Hook Norton
Posts: 18561

United Kingdom 2006 Discovery 3 TDV6 SE Manual Buckingham BlueDiscovery 3

From a forum search, this code appears to be mainly linked to leaking pipes.

https://www.disco3.co.uk/forum/search.php?...lts=topics
 06 D3 SE / 15 LR D90 XS SW / 88 LR 90 Td5 / 68 BMW 2000 ti
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Post #237744716th Sep 2024 11:27 am
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grzesiul
 


Member Since: 11 May 2008
Location: UK
Posts: 6398

Poland 2016 Discovery 4 3.0 SDV6 SE Auto Loire BlueDiscovery 4

he also had C1A20 - 64 which is indication of failing compressor in most cases as I had on mine bus

Wink
G
  
Post #237745016th Sep 2024 11:54 am
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Pauliebanger
 


Member Since: 23 Jun 2023
Location: Lincoln
Posts: 25

United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Loire BlueDiscovery 4

I have removed the air supply unit. Even with my wonky arm it was indeed pretty easy. I was lucky as none of the fastenings put up much of a fight.

The unit is an AMK. There was very little dirt inside the air compressor housing cover, no obvious wire chaffing/damage and no crushing of pipework. The fabrication date shows it is the originally fitted unit. There is no external corrosion visible.

There is no restriction in the air-flow to the inlet from the air filter/silencer pipework.

On the bench the motor runs strongly. The compressor inlet has a strong pull and the outlet has a reasonable air-flow. Though I've not been able to measure the pressure, holding my thumb over the outlet port easilly prevented the passage of air, so I don't think it is generating the expected working pressure. Unless it is escaping from the exhaust port. I ran out of available hands to check this, so that's a job for tomorrow.

I've not yet opened the dryer to check the condition of the desiccant.

I did remove the pilot exhaust valve to inspect the seals (which were OK). Since I don't know what I should have observed regarding valve operation, I can't confirm if it's operating correcty or at all. There are no observable moving parts.

The is a twin pin connector to this valve, what should happen if these are energised?

Paul
  
Post #237747916th Sep 2024 10:02 pm
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Pauliebanger
 


Member Since: 23 Jun 2023
Location: Lincoln
Posts: 25

United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Loire BlueDiscovery 4

Replacement AMK 'type' air supply unit ordered on Tuesday pm.

Arrived before lunch on Thursday.

Fitted and working on Thursday PM.

So I guess the correct interpretation of the DTC is that the unit is faulty. I still don't know what part of the unit is causing this but for now I'm happy to get the car back in more or less working order.

There does not appear to be any major air leakage and the pump runs only infrequently for a few seconds at a time.

I'll be checking out the whole circuit for leaks soon, just in case the cause of the compressor failure was due to over-use in combatting air leaks.

There are no uncleared DTCs

Many thanks to grzesiul and Martin for your advice.

Best regards,

Paul
  
Post #237835227th Sep 2024 8:12 pm
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