Prius Died While changing Inverter Coolant Pump

Hi All,

I am a newbie and joined this group to get a solution for an issue with gen 2 prius.

Long story short. I was helping my friend changing the Inverter coolant pump on a 2008 prius. I did it by removing the left headlight where the inverter pump is located and asked him to open the bolts and remove it while i do other things for him at his place. This is what he told me he did later what happenes.
He took out the old pump and didnt wait for ne to come back. He tried to change it himself. Hekept the engine on while he was changing the pump. He joined the wires in opposite direction and the engine suddenly stopped. I came to check what happened and i couldnt see any lights on the dash. Tried starting the car and could see only the check engine light up for a sec when i push the start button. I checked all the fuses . Tried resetting the ecu by removing the wires off the battery but nothing.
Please note there are no lights on the dash and neither the Information display is working.
When i insert the key and try to start the car, the check engine icon only shows up for a milli sec and other than that i cant do anything.
Any guesses or recommendations for me to fix it for him. He is quite under a shock

 

Thanks for your reply. Am2 fuse is all good. Will be checking the relay integration today.
For the second part yes i dont know why he did it. Sometimes ignorance is not a blessing actually