P0A93 Inverter cooling performance code

The other day I got the red triangle and some of the multi-function display went away mainly the outside temperature part top right corner etc.. It was about 115* outside , Before this happened the car was left idling with the ac on as I had dogs in the car and had to wait for an inspector for a couple of hours. Everything was good drove it home shut off then after about 30 min. had to go another 40mikles got there all good, shut off for about 30 min. re=start then within 3 miles the red triangle appears and I looked it up said to take to dealer in manual. No dealer open after 6pm on friday night. SO I saw a auto parts store they read the code P0A93 got the print out Inverter cooling system performance. I opened up the cap on the inverter bottle it had a lot of turbulance so I said the pump was running however I noticed the fluid/coolant was about an inch low. drove it home at a slower rate of speed no highways this time made it home , shut off next day got some SLL coolant from toyota filled the reservoir to full, put my obdII reader on it it showed the same code , I then cleared the code and the light went off everything as it has been even the display is all back to normal.. So was it just because it was low coolant and very hot and left running for so long , cause I drove it today again and let it idle for about 40 min. no problem and no red triangle or codes appear. Anything I should look for in particular???

thanks very much