SCN Coding

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KevinF

Active Member
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Jun 20, 2012
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83
Location
Hungerford
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E saloon
Whatever MB's official reason for moving to SCN coding might be, the net effect is frankly simply anti-competitive - in other words it forces owners to use MB dealerships rather than independents.

MB may well point out that *anyone* can buy a Star system, but the reality is that the capital cost of the latest version, plus the monthly subscription, means it is beyond the reach of many smaller independent garages.

I wonder if the EU competition commissioner has been asked to take a look?
 
The move to SCN coding was *very* important. There are too many configuration items in every ECU now to have someone set options by hand whenever an ECU is changed, or to understand how changes on one device have to be done on other devices. These cars are really very very complex, and unlike your laptop, if something goes wrong can result in fatalities.

There are software dependancies between different ECUs, and actually loading software into ECUs is now needed regularly - and thus so is up-to-date diagnosis equipment and up-to-date firmware disks too. A simple example is the Audio system. If you update the firmware in the COMAND unit the firmware in every other MOST device needs also to be compatible (if you want it to work reliably) and thus they all need firmware updates. If you change one component then all components need to be updated to be properly compatible.

The latest equipment even now uses ethernet to load firmware into some ECUs (so it takes 20 minutes not 20 hours).

Without SCN coding it would take considerably longer to change any control unit, would result in mistaken configurations, and thus the cost of repair (or re-repair) would go up and up as systems got more complicated. SCN coding basically allows the correct configuration to be loaded into the car.

Imagine what could/would happen if you had to "hand code" the airbag controller after replacing it ? Would you trust all of your airbags to work after the local mechanic had to set all the options correctly ? I certainly would not.

Your comment that "The capital cost of the latest version, plus the monthly subscription, means it is beyond the reach of many smaller independent garages" is just wrong.

If your garage has the skills to deal with the technology (and i'd argue that if they don't they shouldn't be doing complex things with the newest vehicles), then it is completely affordable.

If you want to work on older cars, then most independents seem to use a clone machine and use it for limited things.

The EU competition commissioner has previously taken a good look at this market and enforced rules that mean diagnosis equipment (for newer vehicles) is available at sensible prices. This is not true in the rest of the world. Mercedes diagnosis systems in USA are more expensive, and in the far east (and I think Australia) are not available at all to independents.

Sorry to be so contradictory, and in summary, but without SCN coding there would be mis-configurations and un-reliabilty - possibly dangerous to life - occurring quite regularly. And if you are going to need to work on newer cars, there are very affordable Xentry diagnostics systems - you just need to talk to Mercedes.

Richard
 
...The EU competition commissioner has previously taken a good look at this market and enforced rules that mean diagnosis equipment (for newer vehicles) is available at sensible prices.
£15k plus a monthly sub in the £100s is the cost of the latest Star kit, I am told.

richard;2076192S said:
...sorry to be so contradictory, and in summary, but without SCN coding there would be mis-configurations and un-reliabilty - possibly dangerous to life - occurring quite regularly. And if you are going to need to work on newer cars, there are very affordable Xentry diagnostics systems - you just need to talk to Mercedes..

Ah. Always happy to be informed by the informed. No need to apologise.

Here's my point though: xenon headlight ballast - has to be coded via Star before it will raise or lower aim in response to vehicle pitch sensors. Headlight blinds oncoming drivers unless it has been coded by Star. No option but to visit dealer and hand over wedge. Is that MB ensuring safety or is it something else?
 
£15k plus a monthly sub in the £100s is the cost of the latest Star kit, I am told.

There are other Mercedes supplied options. Your independent just has to talk to the department at Mercedes that specifically supports independents.

Here's my point though: xenon headlight ballast - has to be coded via Star before it will raise or lower aim in response to vehicle pitch sensors. Headlight blinds oncoming drivers unless it has been coded by Star. No option but to visit dealer and hand over wedge. Is that MB ensuring safety or is it something else?

It does not need SCN coding (well certainly on older cars). SCN coding is the "online" bit where the config is needed - which only works with Mercedes supported systems. SCN coding was initially used for engine/gearbox/airbag (as coding them wrong is a disaster, or messes u emissions), then added for the instrument cluster (on W164) as so many got that wrong and menus disappeared, and now for just about everything.

However, It does need Star Diagnosis - and most independent Mercedes specialists have at least one Star Diagnosis "clone" machine which is very much sub £1000 (although interestingly none on eBay, but see Car & Truck OBD Diagnostic Tool China Global Supplier-High Quality, Low price, Fine Service ) - these can do all the testing but as you note less and less configuration. If they don't have one then they are not able to do a proper diagnosis job on Mercedes !

Just to add one extra point, Mercedes make the diagnosis protocols available to makers of independent diagnosis systems (such as Autologics) so that they can develop Star Diagnosis competitors. This again is an EU requirement.

Cheers

Richard
 
I fully agree with the point about the potential for misconfiguration and unreliability, but as someone who has worked in driverless vehicles and aviation all my working life, I think that it's slightly emotive to justify some of M-B's behaviour on the grounds of safety.

Yes, certain functionality in some ECUs is definitely and inescapably safety critical and will be designed and written to the equivalent of DO-178B Level B/C (think of the consequences of cruise control going rogue, or separation radar getting its decimal point in the wrong place).

Those elements of code and equipment will be partitioned away such that the remainder of the vehicle can be changed/update/reconfigured as required without requiring the entire vehicle to be re-qualified.

A simple analogy being that Airbus don’t want a change to the In Flight Entertainment system to require them to re-qualify the Flight Control System software. What they do want to do however is ensure that Blue Ray player type X will work with Controller Y and Screens Z – and that if the controller needs to also work with a particular comms system then it can be coded accordingly.

For that reason a lot of time and effort is put into partitioning functionality such that the (re)qualification impact of in-service design changes can be minimised. That is in all cases except Eurofighter Typhoon where partitioning was done to meet political workshare agreements.

Whilst I’m sure that the entire SCN system is managed to suitably high pseudo-safety-critical standards within the Design Organisation (i.e. Mercedes Benz), I’d be seriously amazed and impressed in equal measure if their dealers have the same level of quality in any ICT device that is connected to the vehicle.

I just don’t believe that the dealers’ ICT is under sufficiently tight configuration control for that to be the case. Moreover I bet that each dealer’s insurer doesn’t realise that they are taking responsibility for safety critical software otherwise their indemnity premiums would rocket.

Instead I suspect that in fact SCN is intended to maintain a degree of configuration control which has, until now been absent in the vehicle industry, and as you rightly say is necessary to ensure compatibility across multiple sub systems.

With the advent of greater levels of vehicle autonomy I suspect that the ‘quality’ standards will have to evolve even more – probably to the point of locking the dealers out of certain systems, but I doubt that they’re there yet.
 
Zulu. I agree with you. SCN was definitely used initially on
SRS (we can understand why mis configuration there is a safety issue)
Engine/Gearbox - to ensure people didn't configure wrongly and cause emissions problems (I think this was because of the USA emissions regulations)

- It has then been extended across the whole vehicle (starting with the instrument cluster on the W164 when it was launched).

The "configuration control" that was enforced between SCN coding was to only allow certain things to be altered using Star Diagnosis (with a password protected engineering mode that allows the very knowledgable support people in Germany to instruct a technician in a workshop how to change other parameters). This still allowed technicians to code things wrongly (and have to have more training!)

As with you, I see less and less control / modification being allowed within the retail/repair "network".

Cheers

Richard
 
My understanding is that the requirement for SCN coding also helps reduce theft of parts from cars - both COMAND and Airbags are quite sought after.
 
My understanding is that the requirement for SCN coding also helps reduce theft of parts from cars - both COMAND and Airbags are quite sought after.

On control units that need 'initial startup' (which is at least those that need SCN coding and probably more on new cars) the process seems to upload serial numbers etc into the Mercedes data card database (VeDOK). For brand new COMAND units it also sends the anti-theft pin to Mercedes. - It maybe just COMAND unit serial numbers are uploaded (as those are all i've checked)

Richard
 
My understanding is that the requirement for SCN coding also helps reduce theft of parts from cars - both COMAND and Airbags are quite sought after.


I am happy to confess that a lot of the above has gone over my head. However, if Mercedes has really implemented SCN in part to deter theft, I have to say I think the strategy has signally failed. And mostly because the biggest thief is MB itself.

Consider:

£360 including VAT for a xenon ballast.
1.5 hrs to fit at dealer hourly rate + VAT
+ SCN coding at prevailing rate + VAT

Thick end of what? Circa £900 to change a component that costs perhaps £15 to manufacture?

That doesn't feel like protecting the consumer and other road users to me. It feels like *bend over and take it like a man.*
 
I am happy to confess that a lot of the above has gone over my head. However, if Mercedes has really implemented SCN in part to deter theft, I have to say I think the strategy has signally failed. And mostly because the biggest thief is MB itself.

Consider:

£360 including VAT for a xenon ballast.
1.5 hrs to fit at dealer hourly rate + VAT
+ SCN coding at prevailing rate + VAT

Thick end of what? Circa £900 to change a component that costs perhaps £15 to manufacture?

That doesn't feel like protecting the consumer and other road users to me. It feels like *bend over and take it like a man.*


As per Richard's post... did you try getting an alternative quote from an Indy who can do SCN coding?

Some Indies will have STAR with the SCN functionality (as Richard does - and he is not an MB dealer...).
 
Hi all,
A few months ago my car broke down. After a long inspection at a MB specialist garage, they gave me the diagnostic. Front Sam unit needs replacement and also The TCU is broken ( speed sensor ).
I had the Front Sam unit replaced with and used one,cause was cheaper (450GBP) but after the car went crazy and multiple errors occurred :

*Without changing gear,consult workshop
*Anti-theft protection activated. Please visit your MB workshop.
*Top up coolant ( which is disappearing )
*EZS (fail)
*ESP (fail)
*AC (fail -not blowing air at all )
* Beltpretensioner - RBTMFR_204 (Pretension front right) - MT/AT
And many more.
Been to a few other garages ,paid for some diagnostics but without any luck.

any help?
 
To fix this you must have an official genuine Star (Xentry).

You may find that a second had SAM cannot be fitted. New only as they maybe coded to the chassis number.
 
I second that. Get it coded (which needs genuine Online Xentry Diagnosis to update the software and set all the settings), and hope the 2nd hand unit you bought is (a) compatible and (b) not broken.

I must say £450 for a second hand unit seems excessive if that was what you paid for the unit itself.

Richard
 
PS, sadly those messages are differing enough that it may be the new unit is crapping on one of the CANbus (i.e it is incompatible/not-working) but it is possible that the installer didn't plug in some of the 20 or so connectors properly too.

R
 
It looks like of the LED light control box of the left headlight broke down. Is it possible to SCN code a used part from eBay to the car? (It is a 2014 w212 car with a static led control unit.)
 
Firstly, I have only done this on the ILD lights but assuming the same then the answer is No. The led controllers come un-configured so they don’t blow up the light. When you configure them you enter the code from the top of the light into XENTRY which then configure the right outputs with the right current. Once configured can not be changed because if u plug in a wrongly configured one it can damage the leds.
So a used one would need to be from a light with the same code on top. I don’t think the vin is stored in them.
Bumper off to change the LED controller as under the light

What’s your VIN?


Richard
 
Thats the wrong part number according to EPC, and Im 99% sure I'm right you can't re-code an old controller. The problem is that if you plug it into the lights and its come of a different car it will put the wrong current down the LEDs and damage them.

Which will be a lot more £ then the £316.80 the new part costs.

Richard
 

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