BRAKE ABS VSC lights. ON

C1241 Low Battery Positive Voltage
C1259 HV System Regenerative Malfunction
C1391 Accumulator Leak Malfunction

C1241 would suggest checking whether your 12 V battery is in good condition. I'll put money that it isn't. You need to use a DMM (digital multi meter) to check a) the sitting voltage with car off, b) the voltage drop under load and the subsequent voltage that it settles at under load (use the headlights on to apply a sufficient load) in IG-ON (not READY) and c) the voltage when you make the car READY. Be prepared to replace the 12 V battery. Once replaced, clear the codes and take the car for a short drive (if necessary) to see if the other two codes come back – I suspect they will.

The C1259 is most likely set because of the C1391. Focus on the C1391, there is an extended warranty on the accumulator pump and you should take your car your preferred dealer to see if it qualifies. If it does, it will be fixed free of charge.

 

b) is low, what were the conditions?

 

12.15 V is ok for the load test as long as it held the voltage over a 5 min period.

Looks like your 12 V battery and inverter are ok (13.8 V indicates the car thinks the battery is on the full side).

Yes, focus on the accumulator. Have you checked with Toyota whether you qualify for getting this fixed under the extended warranty? Another member just had Toyota agree to cover the repair under warranty, so it would be worth checking.