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Can you explain why you think the module is okay?
I connected it without connecting to the motors, and still got a blown fuse... (sorry if I didn't phrase it clearly enough ). To me it looks like the module is not okay, but possibly not just the motor... I still need to check it without the seat recline or headrest motor connectors just in case.
Btw, should I disconnect the battery every time I plug/unplug connectors to the module? I placed it on the floor in front of the seat temporarily, so there's much smaller risk of affecting anything else around like airbag connections. But it it's safer this way, I'll keep doing it.
I did check the resistance on the motors before that though, and here's when it's get stranger... On the driver's side all 3 motors are within 1-2 ohms, but on the passenger's side it's only the seat height motor that's within 1-2 ohms, but both front/back and cushion recline are waay more, around 50 and 37 respectively. Which is something I don't understand. I'd expect faulty motors to have lower resistance, not higher.
I explain it in my post above (3x connectors!!)
> Measuring seat motors:
Whatever value (like 4. to 7. Ohms)
should be in the same ballpark - Not 2. Ohms compared to 60. Ohms
Look at the schematic to know what you are pluging in... I dont think this modules can short its power supply. Meaning you buy a replacement module and it will blows fuses the same way.
De-pin connector if necessary to keep open suspected load circuit.
even a relay melted shut contacts will only keep a motor running non-stop.
To get a high-load you need a short circuit.
Seems like the module is faulty. Tried plugging just the front connector with only 4 wires: the one that comes from the fuse, ground and 2 more going to the CAN bus. The fuse dies instantly. Removed the module, checked the resistance between the fused and ground pins (no connectors plugged) and got 0.001. So there's definitely a short circuit in the module itself. Now there are two questions: can I trace the faulty component or should I try a new module from e-bay straight away, and is it just the module or something else too. Might be time to try direct 12v to the motors.
Seems like the module is faulty. Tried plugging just the front connector with only 4 wires: the one that comes from the fuse, ground and 2 more going to the CAN bus. The fuse dies instantly. Removed the module, checked the resistance between the fused and ground pins (no connectors plugged) and got 0.001. So there's definitely a short circuit in the module itself. Now there are two questions: can I trace the faulty component or should I try a new module from e-bay straight away, and is it just the module or something else too. Might be time to try direct 12v to the motors.
Good job finding a short on the PCB itself.
I double checked your board from pics on Post# 11... nothing that can be replaced easily. (Infeneon interface chip looks like it may have been zapped).
I double checked your board from pics on Post# 11... nothing that can be replaced easily. (Infeneon interface chip looks like it may have been zapped).
Your best bet is a matching eBay unit.
So it's likely a chip, not the relays? I could desolder the relays, but everything else would be more difficult (especially not knowing for sure)...
Do you think I should check the motors just to be sure the replacement unit isn't dead the moment it's plugged in?
the relays are itching you... its not gonna hurt the board worse than a hard short.
(I give it 5% chance relay are the bad guys)
You have wiring diagram just not the schematic. A + B + C
It's easy there are:
A load side
B control side
C board power supply
power interface ??
This chip is my favorite suspect here but likely not worth fixing.
> PLAN B...:
-- Follow the power trace around from the power input pin.
-- Repeat with GND trace input, follow it
-- See where they can meet up to short, open these parts or cut traces so you can jumper back across afterwards.
Last edited by CaliBenzDriver; Aug 23, 2025 at 08:59 PM.
That is a good point!!
I really don't know how/why this module can go into short circuit without self protecting. Voltage surge??
Testing the motors is one good idea - Need to supply the 5 to 10Amp start-up surge.
Don't totally trask the board into a doorstop because you may need to harvest coding chip for the replacement unit.
Tested all the 5 motors with a 10A external fuse, all work perfectly in both directions. Looking at the wiring diagram, apart from the motors, power, ground and CAN connections there's an Easy-Entry switch connection with four 0,5 wires. Not sure how to check it.
Thanks for the tip on the module design. I've found a very good deal on e-bay, so hopefully I won't need to repair the old one (fingers crossed).
Tested all the 5 motors with a 10A external fuse, all work perfectly in both directions. Looking at the wiring diagram, apart from the motors, power, ground and CAN connections there's an Easy-Entry switch connection with four 0,5 wires. Not sure how to check it.
Thanks for the tip on the module design. I've found a very good deal on e-bay, so hopefully I won't need to repair the old one (fingers crossed).
Nice progress!
Now you have good confidence to believe the working motors won't fry your replacement module.
The log will read... original unit shorted out for unknown reason.
Last edited by CaliBenzDriver; Aug 25, 2025 at 08:29 PM.
@CaliBenzDriver and @znd I have learned a lot reading your troubleshooting. Thank you for sharing with the forum. I hope the replacement board works as plug and play. Odd that the board has some short in it and can’t locate where it is. Semiconductor chips don’t fail that often so not sure if it’s control side, load side or something to do with power supply side. In any case if this issue ever happens to me I will refer back to this thread. Looking forward to the good news from @znd that everything is in working order again once he tries the replacement board.
@CaliBenzDriver and @znd I have learned a lot reading your troubleshooting. Thank you for sharing with the forum. I hope the replacement board works as plug and play. Odd that the board has some short in it and can’t locate where it is. Semiconductor chips don’t fail that often so not sure if it’s control side, load side or something to do with power supply side. In any case if this issue ever happens to me I will refer back to this thread. Looking forward to the good news from @znd that everything is in working order again once he tries the replacement board.
These cars are not misterious... you can do a lot of good with basic tools, schematics and helpful MBWORLD connections.
The key is to identify what you're dealing with and grow more focussed from there.
Last edited by CaliBenzDriver; Aug 27, 2025 at 12:58 AM.
Now you have good confidence to believe the working motors won't fry your replacement module.
The log will read... original unit shorted out for unknown reason.
So the module arrived. I'm not sure which car it is from, as it was advertised as w204, the listing photos had w212 handwritten on the box but mine arrived without it. All hw/sw versions/revisions, as well as the board, are identical to mine (see photo).
First, I plugged just one connector - with power and CAN B pins - to make sure it doesn't blow the fuse. Then disconnected the battery, plugged 3 more connectors (and the battery of course) - and nothing. The fuse is okay, the passenger door buttons won't do anything, folding the seat doesn't move the seat forward. And then I thought I'd try buttons on the driver's side. And they move BOTH seats. What's even funnier is that 4 motors (back recline, headrest, seat height and seat angle) work in the same direction, but the back and forward button moves the seats in different directions:-/ Even memory buttons work for both seats. Folding the driver's seat doesn't move the passenger's (or it would be too funny).
Looks like I need some coding:-/ Will the Launch Creader do the job do you think?
yes, you need to code the replacement to match what your car expects.
Connect original module with just enough pins for power and CAN.
Backup the original configuration with scanner
Switch modules with replacement
Write the iriginal config onto replacement.
Connect all connectors... fuse stays solid ?
Lastly clear faults...
enjoy your repair.
The problem is, I can't connect the original module with power and CAN because there's a short circuit between the power pins. I did order Creader, but I'm not sure there'll be much I can do
The problem is, I can't connect the original module with power and CAN because there's a short circuit between the power pins.
I did order Creader, but I'm not sure there'll be much I can do
You may get lucky with your replacement module matching your car
else you'll need to SCN from scratch
or perhaps get original coding cheap physically transfered via soldering.
You may get lucky with your replacement module matching your car
else you'll need to SCN from scratch
or perhaps get original coding cheap physically transfered via soldering.
So I got Creader Elite. It does see the new module, doesn't see errors for it, can run and finish normalization (the seat does move), but the passenger door buttons still don't work, the driver door buttons still work for both seats (in sync apart from moving the seats back/forward where they move in the opposite directions), and folding the seat still doesn't bring the seat forward. I've also tried the actuation test, and with the seat back F1 brings the seat forward (F2 backward), but for the seat itself it's vice versa. I've also tried changing separate settings like Easy Entry (it's active for driver but inactive for passenger seats) or setting the body type for the module to "coupe" (it opens as "sedan" for both driver and passenger seat modules, which is quite weird) but the changes don't seem to be stored - the next time I access these setting I still see Easy Entry disabled and the body type still opens as sedan. I believe Creader should be able to change settings, shouldn't it?
Is there anything you can suggest except soldering or ordering another module with higher chances of being from the same model?
So I got Creader Elite. It does see the new module, doesn't see errors for it, can run and finish normalization (the seat does move), but the passenger door buttons still don't work, the driver door buttons still work for both seats (in sync apart from moving the seats back/forward where they move in the opposite directions), and folding the seat still doesn't bring the seat forward. I've also tried the actuation test, and with the seat back F1 brings the seat forward (F2 backward), but for the seat itself it's vice versa. I've also tried changing separate settings like Easy Entry (it's active for driver but inactive for passenger seats) or setting the body type for the module to "coupe" (it opens as "sedan" for both driver and passenger seat modules, which is quite weird) but the changes don't seem to be stored - the next time I access these setting I still see Easy Entry disabled and the body type still opens as sedan. I believe Creader should be able to change settings, shouldn't it?
Is there anything you can suggest except soldering or ordering another module with higher chances of being from the same model?
I strongly suggest to SCN Code that working module so it matches your chassis options.
No two ways around coding as your original module is shorted out and you said no soldering (to transfer original chip).
Could you explain SCN coding in a bit more detail? I'm not really familiar with it unfortunately.
Soldering can be an option, but a software solution looks a bit easier, and I don't even know which chip is the coding one
Mercedes use the same identical modules on 40 different chassis.
SCN level coding configures the module to match your installed options.
All new modules can be programmed
Some used modules can not be reprogrammed (solder!)
Last edited by CaliBenzDriver; Sep 3, 2025 at 08:09 PM.
yes and you wrote the module was not accepting your changes.
Seems like Creader just doesn't support SCN coding. When I choose "special function", which opens this body varian/national version/year prompt (pic 1), there's no "write coding" button that I see under "variant coding" (pic 3). So "special function" doesn't write anything, just allows to choose 3 options potentially specific to the chosen model/version/year (pic 2). With individual settings it's different as I've managed to "write coding" after changing the direction of the seat position motor - now both seats move in the same direction when I press the driver door buttons.
I can't find a description of all the individual settings, so it seems like I either have to find an SCN-capable software, or consider soldering. Do you think desoldering the 4 relays and the chip that you thought could be the reason of the short circuit is likely to make the original module readable by Creader? This way I could back up the original configuration and potentially restore it to the new module. Looks a bit safer than soldering the configuration chip (unless the suspicious chip IS the configuration chip).
this menu is where you have a chance to configure the module for free and not have to pay to get it SCN'ed.:
VARIANT OPTIONS ... WRITE CODING
it's the screenshot for the driver seat (N32/1, as opposed to passenger N32/2) and I believe it's inactive for both. I was a bit surprised to see "passenger" here for both modules, not just for the passenger seat module..
I made a table of all variant coding values for both modules just to compare them. No sure what LES/LNS or "LS V/Z Motor"/"LS H/T Motor" are.
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). To me it looks like the module is not okay, but possibly not just the motor... I still need to check it without the seat recline or headrest motor connectors just in case.
