Okay, be nice to me as I am a new driver, new car owner. I recently purchased a 2007 Prius from someone I knew. The car was pretty roughed up, but was said to have the hybrid battery replaced a few years prior to me getting it. It sat for around 2 years before I bought it and drove it. My dad is a mechanic so her tuned it up and it drives great. The only issue I have had at all is the check engine light (o2s, not a huge deal and will be replaced) and the RTOD. I have been reading many posts here and elsewhere about what it could possibly be because it comes on and drives fine still, and goes away again. I noticed it coming on when I have driven it for a while (40ish minutes or more) in the heat (in Minnesota, so anywhere from 85-100 F) and usually if I'm doing stop and go on city roads or traffic. The triangle goes away after the car has cooled and the battery has been reset. It does not go away if it's just cooled but not reset, but won't come back on if I reset it until I drive it in the extreme heat again. There's no heat warning showing up, and just the red car with the exclamation point on the center console. I got myself a OBD2 diagnostic interface and ran tests with the dr.prius app and no codes came back at all for the battery, but I ran them when the triangle was not on the dash anymore. I replaced the air cabin fan and filter not that long ago as my AC didn't work and now it works great. But the triangle came on the first time I used the AC. I'm just at a lost point currently. I only paid $2000 for the car so I'm not trying to take it into the dealer to get fixed (it's quite a bit roughed up cosmetically as well and I know as a woman the dealership with rip me off big time anyways) the car has 270,000 miles on it but is running fine otherwise. Any ideas on what to do?