Here is the step-by-step instruction on writing Benz W140 chip using CN900 46/48/4C/4D auto key programmer and CN900 Pro 7935 chip.
If you download CN900 PC software to work with CN900 key copy machine, CN900 can save the read key code data unlimited, read EEPROM and special transponder, like Mercedes-Benz W140 transponder chip.
CN900 key programmer
CN900 PC software (can be free downloaded from official website)
CN900 Pro 7935 chip (for CN900 only)
Select chip type: 44 Philips CRYPTO
Mercedes Benz C.E master transponder key programming
Select key number, press OK
Click on “PIN CALCULATE” button
W140 chip has been successfully read and written