SCN (Software Calibration Number is used to prevent unauthorized / Benz authorized maintenance factory to make unnecessary software update system failure due to (chaos update of the car is really will brick…)
In fact, SCN coding also has the meaning of preventing unauthorized parts circulation. On W204, such as dashboard, gearbox, computer, etc., the main parts must pass through the SCN coding to synchronize with the car ECU, otherwise it will not work properly.
Before you start SCN coding, you have to issue a SCN request to the Mercedes Benz Corporation, and there are two ways, Online and Offline,
Online, your DAS / XENTRY must have a network connection, and you must have the valid user name and account number of STAR NETWORK, basically all online homework It will go into the vehicle database of the benz server to make a query and determine whether it is a legitimate and necessary SCN, and then send it back to you with a SCN code.
Offline is the use of DAS/Xentry without network connectivity, but must be completed according to the application form, Email or fax to the German Mercedes Benz Corporation, they will be audited to send a group of SCN coding, so that the maintenance factory can do Offline SCN coding.
Basically SCN coding was necessory since W204 (2007) W212 W221 W207 and other compents need to replace, so it doesn’t have to worry about theft of main parts of the problem,
On the W204, you need SCN coding parts, dashboard, airbags, transmission computer, ECU (CGW), front and back SAM, and so on
Parts COMAND APS, rearview mirror, steering wheel…without SCN coding and high theft rate ~!
Xentry DAS (Diagnostic Assistance System) is the complete diagnosis system that is used to troubleshoot Mercedes-Benz car problems and is the official Mercedes-Benz dealer software. It can configure, reprogram, initialization of new components, program, perform guided tests, read or erase fault codes in any of the systems including AirMatic, AirBag, SRS, EIS, Transmission, ETS, BAS, and all of the control modules. DAS Xentry software requires the C3 Multiplexer Star or C4 SD Connect hardware. The c3 multiplexer is an earlier model that was replaced by the C4 SD Connect. To operate Xentry, you will need a laptop with a serial port RS232 to connect the Multiplexer and run the Xentry software. The online marked is flooded with pirated versions of Xentry Diagnostic scanner, so be careful and avoid those hacked versions. Online merchant which may not be authorized resellers, distribute the software and show you how to install Xentry as you can see on this guide.
Why Software Calibration Number (SCN) Coding is important?
Because if you are experiencing trouble with your transmission, there is a good chance that the problem is with your ME Control Unit and that SCN coding is needed to resolve the issue. Unauthorized technicians can not fix this problem because only certified technicians can access the Mercedes-Benz server.
Why all work on your Mercedes should be done by a technician who is SCN certified.
SCN coding is required to update the software when a new Electronic Transmission Controller (ETC) or fuel control unit (ME) is installed. In a majority of the systems in Mercedes Benz, SCN coding is required after the replacement. These systems include; SRS airbag computer, 722.9 gearbox computer replacement, Gearbox module, SAM computer, ABS, ESP control unit, the COMAND system, intelligent headlight computer instrumentation, and ME modules, among others. All these systems require the network authorization from the Mercedes-Benz Technical Service Center for the completion of the process. Unauthorized technicians can’t do this.
Why SCN Coding Services Are Needed
SCN coding is required for a number of reasons. First of all, it is required by law; you may also be fined if you have not performed this crucial step. Secondly, you need this if you want to make sure that your vehicle works at optimal levels. SCN coding is also required to prevent any aftermarket enhancements that are done to improve the performance. If you want to install additional control module in the future, it will require SCN coding.
Here are some of the things that happen when you need SCN coding. First of all you check engine light will be on. You may notice that your transmission gets stuck in a 1 gear. If you turn the engine off then on again, this may resolve the problem, but only temporarily, then the same thing happens again. You may also feel a kick when you shift into drive or reverse. Any of these could be signs that your Mercedes needs SCN coding.
How it Works
The repair process of the ME control unit requires the technician to update the software in order to solve the real issue. Now, to update and correct the software programming, you need to re-code it with the help of SCN Coding. To repair the ME control unit two steps are required; flashing and updating the software by using the Software Calibration Number (SCN). However, most independent Mercedes Benz service shops cannot perform this process of updating Mercedes Benz ME control unit SCN because only the authorized technicians can access Mercedes-Benz server.
Why flashing is required in the updating process of Mercedes Benz ME control unit software? In simpler terms, flashing is a method to update the ME control unit software. Flashing would be required in many circumstances; for instance, in cases when your DTB requires the software to be updated, when TAC/EDAC requested the updated software, if there is any part with new ECU number or when a new Mercedes Benz ME control unit is identified by SCN.
SCN system definition
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 behavior 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.
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!)
I see less and less control / modification being allowed within the retail/repair “network”.
SCN coding importance
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.
The Mercedes Benz online SCN coding hardware: MB SD C4 / C5
The software version of Xentry DAS is able to do SCN coding: Xentry DAS V2017.11, V2017.09, V2017.07
For the users who own mb sd c4 software v2017.07 or v2017.09 or v2017.11, you just order SCN Online Coding service
If you MB SD C4 software is before than V2017.07, you are advised to buy the newest sd connect C4 update software, then order SCN Online Coding service
UPKEY SCN Online Coding service Feature: convenient and fast, online authorization login via usbkey.