Share my real experience : Yesterday try to replaced EIS in W212 with other used one, not exactly the same part number, but with help of EPC was replaceable
Orig EIS + 1 key functional (orig EIS have some malfuctionals, sometime ok, sometime not, but all keys data readable yet) calculation key password online, get erase password success – all data saved
Other used one EIS from scrapyard, no any keys, then through step: W212 all key lost to get key password, get erase password – all success
then renew this EIS with all valid passwords – success
read all EIS data from orig part and as first write VIN, then write all key data ( the process is almost the same as when teaching ELV or Emulator unit to W204)
use orig key and NEW EIS is success activated
all work with both EIS are on the table, without car !!!
put new(used) EIS back to the car and need little time wait for key recalculating to car, then turn to first ignition position and again wait for recalculating….
at end turn to 2nd ignition lights OK, again wait for recalculating in ECU, after message away try turn key to start – car start, all okey
Remote lock/unlock work, no any problems…
With ELV steering locking unit All work on W212 from 2009 year !