Red Triangle/Red Battery/Red Car icons + 10.9v 12v

I've had an 07 since 2018 that's been great minus an ABS actuator replacement I diy'd a few summers ago, but it's been acting up lately. I had my power brakes 'go out' a couple months ago, which ended up being my fault, brake fluid was below the low line and I didn't notice it. I got that refilled and it was fine and then a week later it lit up with warning lights and I read them manually with the blinking system and saw C1241 (Low Battery Positive Voltage or Abnormally High Battery Voltage). I checked my 12v voltage and sure enough it was sitting around 10.8-11v while checking through the touchscreen menu you can get into that will read the voltage.

I had oreillys test that battery, which I had bought from them a few years earlier, and they said it looked fine and just needed to be charged up. I was sick of dealing with it and decided I'd just buy a new 12v battery from Toyota to ensure the 12V wasnt going to be an issue. That was about 2 months ago. It was fine until today when I went to start it up and got the red triangle + the red battery icon, the car with the ! icon, and a check engine I believe. I have an MX+ bluetooth OBD2 scanner coming in later today, so I cant read any codes yet but will post what I find. Haven't had any issues with the hybrid battery discharging fast/not charging up how it normally does/etc but we will see if it's having issues when I can read the codes.

One thing I did notice is that my new 12V is reading 10.8-10.9v when checking it through the touchscreen menu again. It drops to 10.1v when the headlights are turned on and jumps to 14.4v when the cars turned on, so it is at least getting a charge. However, I read the 12v voltage manually with a multimeter and was getting a low 11.5V reading, but when jumping into the car and testing it through the menu, it shows 10.8-.9 volts. Not sure if the discrepancy is normal.

Any ideas here? I havent been making longer drives in the car, usually around 5-10 miles at a time multiple times a week ever since it started giving me problems. I dont trust it on longer drives and have been using a different vehicle for those. Prior to all these issues, I was putting around 600-900 miles a month on it. I dont know if the shorter trip duration is not fully recharging the battery (may need to buy a charger and juice it up once a month?) and/or I got unlucky and got a faulty 12v or if something else is going on.

Obviously the codes will help a lot, but wanted to brain dump this and will update it when I have more info. Thanks!

 

Thanks! I got the MX+ OBD2 adapter and ran a full scan and it had two P0A08s popup this morning, which seems to be a fun one to try and track down. The red triangle and warning lights did not appear this time. The engine ran some to charge up the hybrid battery while scanning, after the scan I checked and my 12V was at 11.9v through the diagnostic menu.

Found the repair manual and the trouble areas are:

• Auxiliary battery
• Fusible link block assembly
• Fuse (for 12 V electrical
equipment)
• Engine room relay block
• Inverter cooling hose
• Water pump with motor
assembly
• Cooling fan motor
• No. 2 cooling fan motor
• Wire harness or connector
• Inverter with converter
assembly (DC / DC
converter)

I can hear the inverter pump running and saw the fluid moving around so that seems fine. Checked the 12V and the connections were tight and the 5A fuse looks good.

Will have to do more digging to try and determine what's going on. Will likely take the 12V to Toyota and have them test it as well.