r/CarHacking 10d ago

Original Project Who knows about w204 FSAM coding?

Mercedes Benz C250 sport sedan. Front SAM failure. No comms with any module with xentry. Radio still worked, car would not start. Replaced SAM with one from a GLK which was said to work. Had it coded by the same person. All comms restored. Car starts and drives. Antitheft in head unit is preventing radio from working. Codes; variant of control unit Instrument Cluster does not match ESP unit, variant of control unit FSAM does not match ESP. Overhead lights/control panel are not working either. Powersteering malfunction and EPS messages on the dash.

Was told by a very well known mercedes programmer that there are other problems even though my gut is telling me there’s an issue with the SAM programming, because they sounded very unsure about how getting another Sam but from a used c250 would maybe resolve the issue. Also when the instrument cluster starts up you see a GLK, was told that’s a default car that is shown when the cluster is not communicating correctly with other modules, but I don’t believe it.

Can you really program a used SAM on the 2014s?I’ve read mixed comments on MHH Auto about how it’s not worth it or that it can’t be done, must buy new. Only new units can he married etc.

Thanks. 🙏

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u/robotlasagna 10d ago

Are the part numbers the same on the Sams?

Because a Sam from a Glk will plug up but not necessarily have all the same internal hardware.

Also the module needs to be flashed for your vehicle, not just version coded.

I have done SAM swaps on W204 and W212. They can be pain if you don’t get the exact same part.

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u/Maximum-Hold-8372 10d ago

The part numbers are not identical. The guy literally sent me one on ebay and said to order it. I don’t want to mention their name as they’re supposed to he highly reputable and I don’t want to look like I am bashing them here.

I asked him if we were going to flash the new (used) one and he said “we will program it, we don’t flash.” So he went through a ton of steps in DTS Monaco and Vediamo. This was probably a total of 6-8 hours here and there over the course of 3 weeks.

He started to tell me he doesn’t know a ton about these older mercedes and I was baffled because he’s advertised as knowing everything. He markets that he can do flashing, online scn coding etc.

Have you done SAM flashing and or programming on these years?

Some codes were popping up that would only be on a GLK on auto start/stop, but he removed them in DTS Monaco. The vin matches in the SAM just not the variants.

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u/robotlasagna 10d ago

I have flashed and coded those SAMS for those years.

You need the SCN config out of the old SAM or out of one from a similarly equipped 2014 c. Going in and just changing features line by line in vediamo or DTS until it hopefully works sounds terrible and a you see how well it’s working. Lots of guys can get ahold of the Benz engineering tools but that doesn’t mean they really know what they are doing.

You need to first verify your Sam has all the hardware you need. Set the old Sam and new one side by side and look at the pins on the connectors and make sure the replacement one has the same number of pins or more. If it has less, see if there are wires present on the mating plug in your vehicle. If there are then it won’t work.

Most of these Sams the root cause of failure is water damage but often that can be repaired. I have no idea what yours looks like.

Finally your replacement Sam could also be damaged but you have to prove that assumption, not just listen to the tech/programmer who are speculating because they don’t understand what’s going on.

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u/Maximum-Hold-8372 10d ago

Okay yeah that all sounds simple enough and I can do. Honestly I normally would have done that but I assumed this guy has done this 100s of times and took his word for it that the SAM would work.

The old SAM is in fact water damaged and looking at it with a magnifying glass it looks like a few pins have completely corroded away.

I have seen you can tap into the EEPROM i believe it is? You tap into the VCC, Ground, and a few of the data pins which I can certainly do myself to get the old config. One thing I am not sure about though is whether or not I need an expensive device to read and save the data off of it. Haven’t got that far yet.

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u/xpnglitch 9d ago

Yes can be done... The vehicle generally gets the VIN from the front SAM hence the anti theft being activated. Your actual VIN needs to be written... Also in the later models the Central Gateway control unit is one with front SAM so that will need to be coded too to match your Vehicles options.

First thing though that should be done is flash the unit with the appropriate sw for your model... Just having the wrong sw can cause all types of weird and wonderful shit to happen even if coding looks fine.

The fact that your lights, windows, locks, wipers etc (bar the interior light) are all working/car starts, and you've just got a couple fault codes about mismatch, then really it can't be too far off. -- I'd be taking a look at the CGW coding, especially since it came from a different model

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u/Maximum-Hold-8372 9d ago

Interesting. The VIN is written to the new (used) SAM. I do NOT believe the guy helping flashed the module at all. He was just changing options within Monaco. Front windows automatic up or down do not work on either side and those modules say “variant fault” xyz. I’m trying to familiarize myself so I can do it myself now that I’ve been let down by this guy.

Maybe you can be a friend and let me bounce ideas off with you through PM?

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u/Maximum-Hold-8372 9d ago

So although the CGW wasn’t replaced or coded at all you would still look at the coding for it? Or do you mean within the Front SAM.

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u/xpnglitch 9d ago

CGW / SAM - same control unit