This is special function for using with Universal Decoding Tool for Renault fuel injection ECU also known as Renault Immo Tool. This function available only for using with TYPE-1 immobilizers.
Select Semi-Auto operation mode (fast green LED blinking). Press START button. After every ignition-on, MIL immediately starts to blink fast. Watch the ECU MIL lamp and count number of ignition-on (start counting from 1). Note number of ignition-on cycles when MIL stops blinking for a while.
ECU is not decoded after this procedure, you only found out its security code. In worst case when MIL stops to blink on 254-th ignition-on, counting takes about 8 minutes.