Hello! First time poster here. I have a 2007 Prius with about 190k miles on it, got it used almost 2 years ago. The HV battery was replaced right before I bought it and I haven't had any issues with it. I was recently driving and got the red triangle of death. I drove it off the highway and got it towed to my place. I got a Autel MaxiAP200 code reader and it returned a P3000 (INF 123), P0A1F (no INF code) (Battery Energy Control Module), and C1241 (no INF code) (Low Battery Positive Voltage or Abnormally High Battery Positive Voltage) The car still drives fine, no noises and it is not in limp mode. The report I pulled first showed battery Block 4 and 8 to have lower voltages than the others and the range between the lowest and highest block was about 1.15V. I later drove around to watch the live data of the HV battery cells voltage and they all seem fine. None are more than 0.5v out of step with any of the others while at rest or under load. I attached a report I just pulled while the car was in ready mode, at rest. I took the 12V battery to AutoZone to get it tested and they said it was good. When I tested with a multi-meter I got a 12.18V reading with the headlights on while in accessory mode. That seems fine but I'm not sure if Prii are more sensitive to lover voltages in the 12V? After reading other posts on here I took a look at the Battery ECM connector. There's some corrosion on some of the pins (pictures attached). But, it doesn't look burnt as I have seen other posts on here show then there are battery ECM problems. Would corroded pins lead to a P0A1F? When I removed the 12V battery to get it tested the codes reset. The only one that has consistently come back is C1241. P01AF has not returned even after driving around to observe HV battery health. I got a red triangle a few months ago and had to replace the inverter coolant pump, which still seems to be working. I am not sure where to go next here in diagnosing the problem. (I was hoping wither the 12V was bad or that I'd find burnt connectors to the Battery ECM). Could a low 12V cause a P0A1F? Should I try replacing the 12V and/or the Battery ECM? Or is it the HV battery going out?
how old is the 12v? if they did a load test, it should be fine. the low voltage code is often because of corrosion on the pin connectors is keeping full voltage from passing. or it can be anything along the route from the 12v to the ecu
If the problem remains, the next things to check are covered in the Repair Manual section for C1241 and the wiring diagram (more info).
