Watch ? very simple ! we start from the assumption that you have the necessary to the reading of the Flash , and then read the flash in boot mode the ecu that you want to scodificare partially, after the write always in boot mode the file that you can retrieve with carsoftware , then mount the control unit on the machine and turn on the ignition , wait a few seconds after you disconnect the ecu and rewrite the flash in boot mode of reading done initially , and then mount the ecu and you have done everything correctly, the engine starts.
If you follow all the procedure you can write your own like the flash of both units .