Just got a HV system message. Is there anyone understand japanese?

You could be doing way more damage to your car by continuing to drive it. Just because you don't speak Japanese doesn't mean you should ignore it and keep driving. Once the error codes are read you can make an informed decision about waiting for repairs or driving more.

 

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Look into a compatible OBD2 reader for this vehicle, then you (or the mechanic) won't need to learn Kanji

 

My speculation is the inverter pump has failed.

HOW TO CHECK INVERTER PUMP:
1) Prop open engine hood.
2) Open inverter reservoir (that opaque coolant container, next to the big square silver thing in the middle of the engine compartment).
3) Visually look inside the inverter reservoir. NOTE the calmness of the coolant inside this reservoir.
4) Make the car IG-ON or READY.
5) Visually look inside the inverter reservoir again. Do you see fluid movement? It should have a flow rate like a calm tranquil stream.
6) If it is quiet enough, you may even hear the inverter pump; its sounds like an aquarium air pump.
7) DO YOU SEE FLUID MOVEMENT in the inverter reservoir? Do you hear the inverter pump? If yes (fluid movement), Inverter pump is GOOD. If NO (fluid movement), inverter pump is bad and needs to be replaced.

A failed inverter pump will produce different symptoms (ie A/C shutting off) and the same warning icon, with English
( ) on the MFD (Multi-Function Display) in the top left corner, when the inverter begins to overheat.

 

You may want to download an English version of the Prius Owners manual. Try the Toyota UK site, as the UK Prius will be most identical to your JDM Prius; My Toyota | Toyota UK

As a back-up, try Toyota USA; but there are some differences between a USA vs JDM Prius, besides left vs right hand drive position.
Toyota Online Owners Manuals and Warranty

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