I have a 2005 Prius. I drove it to work and as I was leaving the dashboard lit up with all sorts of warning lights including the dreaded red triangle. I had to leave it there for a couple of days until my boyfriend came to look at it. He drove it to autozone because he didn’t have his code reader. He turned the car off and when he came back outside, the car was completely normal again and said nothing was wrong. We got it back to my house and had to leave it there for a couple days. This weekend all of the lights came back on. We took out the fan, which was relatively dirty and cleaned it out. But then we test drove it, turning it off and on a couple more times, and all the lights came back on. Then two more codes popped up C1310 (malfunction in HV system) and C1241 (abnormally low or high battery positive voltage). And we turned it off a couple more times and the C1310 went away. The fact that only the replace hybrid battery comes up makes me think it’s not that the whole thing needs to be replaced. When the lights are off and it’s not showing a code, the car is fine, drives normal, and it screen shows it charging normally. When the lights are on and it’s showing a code is when it acts weird.
welcome! start with a load test of the 12v health check the inverter fluid reservoir for movement with the car 'ready' then get tech stream diagnostic software if you're gonna diy if the hv battery is bad, it never goes bad altogether. it's made of of modules that fail one or two at a time. but at your age, they will continue to fail you can get a prolong grid charger to restore some life, but you might be better off dropping $1,600. on a new battery all the best!
I assumed that it was the battery, but then reading other people’s experiences, they said the code reader specifically said the certain cells were bad. The code reader only gives the replace hybrid battery. I just wasn’t sure if that really meant anything, like, if it could be something else. Thank you for your reply! I will try those other things this weekend!
More info for the C1241 than you probably want to read....8 pages https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/21avn/cic12414.pdf
What code reader are you using to read the codes? My guess is a generic one that can’t read the Toyota specific codes. Your going to have to get a reader that can read the Toyota specific codes to progress any further.