I

invisible999

Member
What can cause CAN Bus fault and how to fix it?

I am now having air susp inactive/HDC inactive message on 2006 RR HSE US model and only error code ALL COMMS III reads from air susp unit is 0x0032 CAN bus Fault.
 
Odd that your reader outputs in that format - any 'B' codes? I suspect given there is an HDC fault, the cause lies with a wheel speed sensor, wiring to one or a mechanical defect causing the output to be detected as invalid.
The DTC you list is most likely due to a missing message or implausible value being broadcast, not a defect on CAN, if there was, then you'd most likely not be able to communicate with the RLM
 
I don't know what are B codes. Could you tell?

So... what would be the right course of action to fix Air Susp. Inactive/HDC Inactive message/situation?

Just to recap:

1. Front air springs and all 4 height sensors were replaced 3 months ago (spent $2700 on it)
2. Only suspencion and HDC inactive messages are coming on dash. There is no message about limiting max speed
3. I checked fuse #57 in the glovebox, it is fine. Checked (visually, without uplugging) relay in the trunk responsible for the air suspencion, also no signs
4. Looked at the height sensors in front and checked cable connection - seems fine
5. We live in semi-desert area - there was no rain in last 2 months, so there is no possibility that water got it
6. Battery is fully charged and has been replaced 2 month ago with a brand new
7. Message on dash is only about susp/HDC, no message about max speed limit.
 
B codes are body, P codes are powertrain, C codes are chassis and U codes are communication.

The code you are reading is the two byte code direct from the control module, this isn't useful.
You need to be using something capable of reading the whole vehicle and outputting ISO 15031-6/SAE J2012 DTC's. Also, I think you're jumping too far ahead, you (nor anyone else) have not diagnosed the causal defect - you've just read one control module and assumed the stored code points to a fault. In this case, it doesn't, it points to a result due to a fault elsewhere. i.e. the air suspension range/performance is restricted due to missing / implausible data being broadcast on HS-CAN.

You've already stated there is a HDC error message, that points towards the causal factor being the composite speed signal broadcast by the ABS is missing. Generally this is missing because of an invalid wheel speed sensor value.
And that is why you need to read all modules for DTC's and evaluate the output in a human-understandable format as defined in ISO 15031-6/SAE J2012 in order to progress the diagnosis, not get hung up on a 'CAN fault' or a defect in the RLM system - which is performing as expected, given a HDC error.

Edit:- I've just looked at the diagnostic tool you're using, it doesn't claim to work with your model year, which may be part of the issue. From http://www.obdcartool.com/products/Range_Rover_MKIII_-_All_Comms.html
Range Rover MKIII - All Comms,MKIII All Comms

Used to Communicate Withthe Range Rover L322 Vehicle. (2003-2005)

Before Ordering Please check the Last 8 digits of your VIN.

Only MKIII Range Rover Vehicles up to 5A999999 Will Work
Click to expand...
 
Thanks for insights. Regarding the tool - the software the last 8 chars are 5A181916 so the tool should correctly work with them.
Now, I got what I got and if this tool (apparently) does not read what you are saying then I have to take it somewhere where they can and I don't have too many choices in my location.

What DTC stand for?

>composite speed signal broadcast by the ABS is missing

Would in this case there be a message that max speed is limited? I don't have that and can drive 65mph no problem.

I also did check all other components and did not see speed sensor error. Obviously it does not mean that it is not there.
 
So at another forum someone >12 years ago described a problem that looks very similar

www.rangerovers.net

Eas inactive/brake/abs

www.rangerovers.net www.rangerovers.net

Now, the author said at the end that it was due to faulty ABS. Plus he had problems that I did not see - speedometer/etc warnings. But I wonder what might be a contributing factor if you say that Susp/HDC is the result, not the culprint of the probelem.
 
DTC = Diagnostic Trouble Code.
The CAN Fault is a red herring, if there truly was a 'CAN fault', you wouldn't be able to communicate with the RLM to interrogate the faults.... Speed limiting messages don't always occur - and my guess - for it is a guess without any further meaningful information is just that. You really need to move away from the RLM and look elsewhere IMO.
You need to separate the RLM & ABS 'faults' in you mind, they are not the same, I'd say the RLM is a cascade error due to implausible data - most likely from the ABS, but until you can get meaningful data, including live values if necessary, then it's all guesswork.
 
OK, a little bit more information... Today I swapped BCU - got replacement off Ebay - due to all the weird problems I was experiencing with unable to unlock read doors/tailgate, roll down windows, etc. I was getting bunch of
Servo-valve or connections open circuit

messages when reading BCU codes. Once I swapped it, I don't see any of these messages.

However, it did not address the issue we have been discussing - the susp/HDC remains inactive. I cleared codes and read them again and see followin

One more follow-up. Before swapping BCU, I was reading following codes

MKIII Communications Performed by RSWsolutions - All Comms Software.
L322 Anti-Lock Brake Module Query Results: Performed on 7/14/2024 5:05:52 PM
!
Anti-Lock Brake System Fault Reading Complete...

0x58 0x0058 Precharge pump.
Click to expand...

And susp unit:
MKIII Communications Performed by RSWsolutions - All Comms Software.
L322 Air Suspension Module Query Results: Performed on 7/14/2024 5:07:22 PM
.!
Air Suspension System Fault Reading Complete...

0x32 0x0032 CAN bus Fault.
Click to expand...

So, CAN Bus is there again, and now I see this Precharge pump message...
 
1. You never mentioned the other issues, is there anything else you're not sharing? there may be something relevant to your concern.
2. Investigate the ABS fault.
3. Forget about the 'CAN bus fault'.
I strongly suspect that whoever wrote the software put their own take on the meaning of the fault codes to some extent, which is leading to your fixation on irrelevant CAN issues.
 
The ABS code I see is 'Precharge pump'. Is this something related to pump or something else?

I will have to take the car to the dealer and pay $250 just for diagnosing the issue and I would have zero trust based on past performance of mine and other people that what they say is accurate. I would like to avoid this if possible and figure out what are alternatives.
 
invisible999 said:
The ABS code I see is 'Precharge pump'. Is this something related to pump or something else?

I will have to take the car to the dealer and pay $250 just for diagnosing the issue and I would have zero trust based on past performance of mine and other people that what they say is accurate. I would like to avoid this if possible and figure out what are alternatives.
Click to expand...

Hi

Sorry that I don’t know much about the RR , my knowledge is mainly on the D3 however had to do a lot of work on the canbus system, air suspension system etc

Ref diagnosis, there’s one called an Autel AP200 which is very basic but so handy to keep in ur glovebox and only around £70-80

Says it will work up to 2016 but of course no 100% guarantee, just trying to think of a way to save u money , understand dealer prices can run away with themselves so to speak and quickly add up

Also have u done a canbus test using a multimeter

Wished to at least share the info in case it may be useful to u and maybe , just maybe might be able to pin the error down without having to go to a dealer

More than happy to share the details , plus was the battery fully charged before fitting and was the BMS module reset

Will look for the USA Autel ap200 link for u as it seems there are various models , plus happy to share the multimeter canbus testing process with u just in case

Of course many modules if changed would need re programming , not always but can throw the system if modules are changed here and there

At the end of the day u may indeed still may req to go to a dealer , just being honest and upfront with u
 
Last edited:
So found this link, ref the white ap 200, it has live data so u can check things like ur wheel speed sensors etc

www.autelonline.com

Maxiap AP200

Autel MAXIAP AP200 is the new released OBD2 Bluetool Scan adapter with all system diagnoses. It's Cost-effective diagnostic tool for device for DIYers and car hobbyist. AP200 is equipped with its own App -“Maxi AP200”, have superior systems diagnose, support OBD function and Oil/EPB/BMS/TPMS/SAS...
www.autelonline.com www.autelonline.com

See it can also reset ur BMS battery module for when a new battery has been fitted , assume the new battery was fully charged before installation

Plus assume the height sensors were also re calibrated when they were installed and the steering wheel angle sensor was reset , apologises if you’ve been asked these questions before

Might be worth giving the company above a call to ensure it’s compatible with ur vehicle

Hope this may help in a small way with the limited amount of knowledge that I have with the FFRR , just trying to see if maybe the ap200 might show an error and point u in a direction of the fault without having to visit a dealer
 
Last edited:
I can't tell you because the third byte of fault data is missing - the detail of the fault - performance, voltage high, voltage low, etc.

Your comment "pay $250 just for diagnosing the issue" - as someone that 'just diagnoses issues', I'd say it'd be money well spent as your diagnosis tool isn't really doing it for you is it? - it's not all about 'just plug in to the car and it tells you what's wrong', you have to interpret the data, determine what physical checks need to be carried out and have an understanding of the range of expected measured values, have an ability (and the equipment) to carry out volt-drop tests, check data and sensor signals for correct voltage range and waveform along with a host of other system-dependent checks, based upon initial findings.

So yer, it's 'just for diagnosing the issue'.
 
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