Date registered: Jun 2012
Vehicle: 1998 E320 base sedan @ 160kmiles
Location: Boca Raton, FL
Mentioned: 79 Post(s)
Quoted: 1168 Post(s)
The key you show does not have the trunk button which is unusual. Plus the key you have probably has the Japanese standards mark rather than the FCC .
I have not done the transplant but someone on this forum did one for another forum member. It needs masking, heating the chip to remove on both fobs and transfer the one for your car to the new one (precision soldering). But you need to make sure that the microcontrollers have the same part number.
The micro-controller contains an EEPROM where all the car relevant information is stored (VIN, hash codes, sequence number, etc.). It cannot be reprogrammed on the fob, but can be removed, and the codes can be read, and transferred to a virgin chip with special equipment. I do not believe many locksmiths have these equipment or want to invest in them as the volume is to low to make investment financial sense.
It is certainly possible to modify the transmitter network (which is made up of transistors, crystal, resistors, and capacitors) but you need to have the circuit diagram, knowledge of how and what to do, and equipment to test it so you do not have a key that does not work at all.
Here is a typical gen 1 USA key inside. Does your look like the same ?