Red Triangle of Death, Heavy Rain & 12v Battery

This morning the Red Triangle popped up about 5 minutes/200 feet into my daily drive with 2009 Prius. I turned into a parking lot and turned off my engine. It hasn’t been able to start or go back on since. Now, all of the dash lights are on. The brake, swerve, abs,pvc, check engine,and red triangle are now all lit up.

It’s been raining pretty hard in SoCal the last few days and I’ve gotten the red triangle before in the rain. My dad got it checked out and I believe they rebuilt the HV battery last year. I’ve taken some silicone and sealed up as many cracks as possible on my trunks since then.

Also I’ve had the check engine light go on and off for the past week with autozone saying the code meant a stuck coolant valve. I’ve put it off due to work and school and kind of regret it now.

I checked the 12v battery through the maintenance menu and it’s reading 11.7v and 11.2v on ready mode.

Any advice for a broke student on DIY fixes to avoid expensive repairs?

 

Thanks everyone. My dad ended up taking a look at the car and he told me the monitor read "Transmission ____" (English isn't his strongest language) and the the car never came back on again. Any clues from this?