I am sending this post in case schematic was not enough info. for you to understand how to test. I don't know just how knowledgeable you are.
step # 8 using test light connected to Battery voltage test brown wire
step # 9 using DDM check voltage accross both grey wires (Normal is 5 volts)
step #10 wth PCM C1 blue connector disconnected and EGR disconnected using DMM connected to ground (not EGR connector ground) test brown wire for any voltage if there is voltage you have a short to power and needs to be corrected