Engine will not start Volvo xc 70 D5 2004

[Sueday]

Car was lacking power so read about resetting the ecu by connecting the positive and earth battery cables together, left it for a while then tried to start the car but it will not start, when I release the key the check engine light, oil light and glow plug light flash several times, have I damaged the ecu? Any help appreciated

[oragex]

Try boosting the battery - have the key in position II when doing so (also when disconnecting/connecting battery terminals)

[bmdubya1198]

Connecting the battery terminals? I thought resetting the ECU was achieved by completing a drive cycle. I guess that's only for older models.
When you turn to position III, does the car try to crank, like the battery is dead/dying? Or does anything happen at all?