Hi all. I've been a long time Priuschat peruser who now needs some help. Hopefully some of you have had a similar issue and can point me in the right direction before flushing an absurd amount of dough at the Toyota dealer. I've had a 2012 Prius for 9 years and currently at about 290k kms. I bought it in 2015 with 50k and it's been close to bulletproof. I had to replace the heat pump several years ago and that's the most major issue till Fall 2024. It started leaking coolant, which I thought was the head gasket. It sat for about a month, which also killed the 12v (original). I replaced the 12v and, after further investigation, replaced the water pump and thermostat, which seemingly fixed that issue (no more P148F code, no losing coolant). The very next day (early Dec) I went to drive it and had P0A9E Hybrid Battery Temp Sensor A High, P0AC8 Hybrid Battery Temp Sensor B High, and P0ACD Hybrid Battery Temp Sensor C High all come on and went into limp home mode. The last battery health test I did with Dr Prius back in the summer said the battery was about 68% healthy. And I had Toyota test it a year ago and it tested healthy. Side note and perhaps related is the fact that I've had a rodent, I think a rat, in the vehicle off an on for the last couple years and actually spotted it running up the back seat the day the codes came on and found fresh feces in the spare tire well and by the 12v. Any advice or suggestions would be very greatly appreciated. Thank you.
If you feel comfortable working around the hybrid vehicle battery, take out the orange safety plug and remove the covers on the battery and check the wiring for the three temperature sensors. If you are not comfortable working around the hybrid battery, take the car to a hybrid specialist or the dealership.
Thanks for the reply. I don't mind getting close to the battery. I planned to try that and have a look. It's the middle of winter here in eastern Canada and has been really cold. Looks like some milder days coming so I'll give it a go. I've inspected the high voltage and other wiring coming out of the battery compartment and around the 12v and battery fan but can't see anything obviously damaged. Next step will be to get the cover off and have a closer look. I'm no Sherlock Holmes, but having all three sensors tripped at the same time having no issues prior in 9 years, and seeing a live rodent scurrying around the trunk area leads me to believe it's a wiring issue of some kind.
I'd like to think there's no way a rodent could access those wires as they're fairly well covered up. But we can be fairly certain that your symptoms are not because your hybrid battery has gone bad. All signs point to the temp sensing plugs and wires having something happened to them that's causing them to malfunction.
PS: In looking at your error codes again, I'm a bit suspicious about the device you're using to read the error codes. It might be that you do not have the correct error code library for Prius in this device/app. Try checking the error codes with a different app or Toyota Techstream on an old laptop.
Interesting. I haven't thought of that. I had a basic Bluetooth obd dongle that worked with Dr Prius. I've used that app as well as Car Scanner and they've read the same. In an attempt to get a code reader that read the INF subcodes I bought the ThinkDiag Mini and used it today to read them again. Same codes. I haven't found a way to read the subcodes and have a sneaking suspicion this model can't do that. But it does say it can generate a freeze frame, which I hope to run tomorrow.
As long as you verified that its the same codes with different app, then it's correct. Just need to examine and likely patch or replace those sensor wires. There's plenty of videos on youtube about how to safely access and pull the covers on the pack.
The three trouble codes that you have only have one INF subcode, which is 123, so you do not need a scanner that can read the INF subcode. There will only be one troubleshooting procedure in the service manual for each trouble code.
You'll need to remove the rear seats and paneling to access damage. Seems the mouse chewed up some wires and/or made a nest in your battery blower assembly. You'll need to rip that apart to inspect and test. Hopefully it's that simple. You'll also need to find out where that mouse entered the car. Rear battery cooler exhaust port or wind screen HVAC intake port. Use galvanized mesh wire to seal those points off. Either use self-tapping sheet metal screws or a good dalop of construction adhesive. Or you can try this: 12V Ultrasonic Under Hood Mouse and Rodent Deterrent for Your Vehicle Don't know how much of a draw on your battery, but I'd carry a jump pack until you get a good sense of how long you can leave the car, before it kills the battery. Hope this helps....
Thank you all for your input and suggestions. This has been very helpful. My next steps will be accessing the battery and fan. Judging by the feces and collection of nesting material and old food crumbs in around the 12v and under the spare tire, I'm confident that's where the thing is spending it's time. I've cleaned all that out so hopefully it's found greener pastures elsewhere. There was also nesting in the glove box at one point (it actually chewed half the manual cover off and tore open a first aid kit to use the gauze, unreal!) so I removed everything and cleaned it. I assume he/she found another sheltered place to set up shop, ie back by the battery. I'll update once I get time to get at the battery. Thanks again everyone.
Pull your cabin air filter, behind your glove box. Check and clean it out. Debris from your cabin filter can jam-up your blower motor assembly and HVAC directional doors. Any holes in your plastic can be duck-taped over and covered with a thin layer of epoxy to reseal the duct work.
Hi all. Just following up with a question I hope some can answer. Do I have to remove the entire hybrid battery to get the cover off and inspect the temp sensor wiring? I don't mind trying to just get the cover off, if we can get some milder days. But taking the entire battery out will be a logistical challenge since I don't have a garage or place to work on it. Thanks for any info provided.
It's easier to remove the cover than to get to the battery under the seat. When you see this picture, you'll understand which wires are damaged. A mouse probably couldn't get inside the battery.
Hi all. I just wanted to post an update to resolve this thread in case anyone had a similar issue. I ended up taking the Prius into my local Toyota dealer. It's been a brutal winter here and has been steady at -10-20 degrees Celsius since Christmas. My ability to do anything outside without heavy gloves is a no go. The issue was the hybrid battery wiring harness. It had been chewed into. Suspicions confirmed. They ordered a new one for $130 CAD. They also quoted 4-5 hours to install, clean all the rat feces and mess and put everything back together. That part I found fairly dubious. That, along with their code reading of the codes I already read for them, and the hour's worth of "diagnosing" came to $1400. It's working fine for now. Hope that helps someone else. Thanks for all the helpful feedback everyone.
I hear peppermint is pretty effective. A little safer on this kids too I guess. But yes, I plan to do some preventative measures.
Agreed. I'm in now way partial to these things. We were advised against poison because it can be quite harmful to surrounding animals as well. I plan to put a couple traps or sticky pads somewhere around the 12v and under the floor in the hatch if I can. There was a fair amount of crumbs and food from the kids which has been all cleaned out. Hopefully, without a food source, they'll find greener pastures elsewhere. We have virtually no issues around here with mice or other rodents. So I do think this was a one off. Fingers crossed.
