2005 Prius won't start after changing headlight

Good start. I suggest rooting around the area of the headlight and beyond, and checking every electrical connection you can reach. Also, look at the cables to see if any are torn.

The VCI cable and software will help you narrow down the area.

 

Possibly 12v is OK but there are a few things to know about it to rule it out. The 12v charges very slowly during driving so you really need a good long trip or trickle charge to get to full charge. Did he replace with Toyota OEM Prius battery or what? Then there is the diagostics mode where you can check voltages.

 

1. Put a charger on the new 12V battery overnight, to make sure it is fully-charged.
2. Check the tightness of the cable connections to the battery, including the negative cable connection where it bolts to the body.
3. Make sure the 12V battery is securely mounted in the battery tray so that it cannot move around as the car hits a bump.
4. Open up the main relay/fuse box next to the inverter and make sure that all relays and fuses are securely plugged in.
5. Inspect the dedicated positive jumpstart terminal in that box (covered by the red plastic cover) and make sure the 10 mm nut at that terminal is tight.
6. Get Mini VCI so that you can retrieve the DTC logged by your car.
7. If you are not able to find the loose connection then you will need to obtain professional assistance.

 

or go to a toyota dealer, and pay them $100. to retrieve the code.

 

Problem solved, a nice letter of complaint should follow

 

Sorry I somehow messed up the capacity
Alex

 

It's good that you found this. Have you gone over any bumps since restoring this wiring harness connector - to verify that this was the root cause?