W211 airbag controller replacement

[connashio1]

Hi all,

I have an intermittent fault on my 2003 W211. The SRS alarm light comes on and passenger airbag on light goes off, and was thought to be the seat occupancy sensor pad in the passenger seat.
My local Merc specialist has tried 3 emulators and the problem does not go away. With his laptop plugged he can see alarm messages (I don't have the details) reporting. This happens with the emulator fitted and with the seat connected. The only think left that he can give as the cause is the controller unit.
As a new OE one is £500 he suggested getting a used one. The question I'm having trouble finding a definitive answer to is this. Can a unit from another be coded to my car? If not I have to buy an OE one and hope that really does fix it.

Thanks, Paul

 

[connashio1]

Has anyone bought a secondhand airbag ECU and had it coded to their car? Or have I just wasted £20???

Cheers, Paul

 

[connashio1]

I found out the answer.......

 

[Petrolheed]

Just read this thread, the srs ecu is coded to the car, I think the selector module, EIS, Instrument clsuter and the SRS module have VIN specific coding, but not sure if you can re-code a used replacement SRS ecu.

 

[Salal]

There usually isn't a easy fix when it comes to these sort of problems, unless if you have the right tools.

All modern ECUs are interlocked to the car they are fitted to originally with the VIN being programmed into the ECU and even if the one you bought is the same part number. it will most likely be incompatible to your car as depending on your car specification each will have different software installed accordingly and now SCN (Software Calibration Numbers) come into play as well and most new ECU's supplied by MB will need this carrying out after installation.

Usually, an old ECU cannot be brought back to factory state to be fitted to another car. Even the official MB star diagnosis can't do it. However there are other tools which some are factory Mercedes programs such as Vediamo which dealers don't really have access to anyway and some after market tools which can do it. If you look around you might find someone that can help you out. But with SRS systems its best to go to the dealer if you want to go down the route of a new SRS module, as you'd be surprised a lot of people do dodgy repairs and its the one thing you'd want to work properly if you ever need it. Another option is to send it off to someone and they can copy your original module and transpose it with all the relevant data into the new used one which will make it work. But don't be surprised if the used one is also faulty which will just confuse things even more with the troubleshooting.

Sometimes its best to just bite the bullet and go to the dealer if you don't have any other options.

Did your indy check the wiring to/from the seat as wires are common to chafe/break around there due to the movement of the seat over time.