In this video I will take you through the process of reset, (also known as Tech2 reset), and reprogramming of the engine ECU on a Vauxhall Astra H 2004.
You can follow the second part of this steps, if for example, you are replacing the engine ECU with a second hand one, or even with a new ECU, although in this last case you might need to program the calibration software.
Hope you enjoy the video.