Red Triangle 2009 Prius, Hybrid or Aux?

Hi I've recently gotten the red triangle twice. First time was on the highway in the middle of a 1 hour commute. The car wouldn't go over 45 mph so I got off the highway. I was able to make it to my destination and later all the way home by not running the AC to conserve power. I drove the car for several weeks after that (although with covid I only drive short distances a couple times each week)

Then recently I started another trip, but only got about 5 miles before getting the triangle again and drove back home. I put the car into diagnostic mode so I could see the voltage. In park it was showing the voltage as 13.9v but as soon as I put the car into drive gear the voltage dropped to 13.3v.

Is there a simple way to diagnose if it is a hybrid battery issue or Aux battery issue? The car is 11 years old, I've only owned it for about a year and I'm not sure if either battery has ever been replaced.

Also I'm wondering if anyone knows anything about the Dr Prius Lithium Iron-Phosphate batteries. If I'm going to put in a new battery I would consider that option. Thanks!

 

Prius-Codes by TampaToma posted Jul 31, 2020 at 10:36 PM

 

When I put the car in Diag mode tonight the voltage on the Aux battery was 12.1v. When I put the car in Acc mode it went down to 11.8v. When I fully turned the car on it went to 13.8v. I drove the car around the block and red triangle disappeared. Before that I used the Dr Prius app and got the codes shown in the screenshot above.

 

126K Miles and no water in the cabin area that I know of.

 

The P0A1D refers to the hybrid powertrain control module. I tried to do research on this code and was surprised to find not much info on it. The most important info I found was in this screenshot on a car repair website. It has me very intrigued so I'm going to take a look at my AUX battery and check the connections. I also ordered a NOCO Genius5 12V battery charger and will try charging up the AUX battery. I'm thinking maybe it got weak from lack of use during covid. Also I do remember once a month or so ago that my smart key stopped working randomly one day and I thought it was very odd, but then it started working again a few days later. seems related to this issue I'm having now.

If none of my tinkering uncovers anything obvious I will take it to my mechanic to have the codes looked up on techstream. Thanks so much for your input!

 

Wow! Thank you that is super helpful. I did take all of those connectors out yesterday and inspected them and didn't find any corrosion. I will double check again now that I have these pics and know exactly what to look for. Also took the front kick panel off and looked there as well. I hooked the battery up to a battery charger and let it run for about 6 hours last night. The charger indicated that the battery was full so I disconnect the charger and checked the voltage using the car's diagnostic screen and it was only showing it at 12.0 Volts and as soon as I put a small load on it (stepped on the brake pedal) I saw the voltage dip to 11.4v, so at this point I'm thinking it's just a totally dead aux battery. I'm going to order a battery and try that. The charger I bought also had a battery repair feature that I might try as well, but at least I will have a backup battery on the way.

 

Can you explain what you mean by "R+Ring?"

 

hmm... a red car? I believe I did when I was having the issue. The codes have all cleared now. I've ordered a new 12V battery that should be delivered on Wednesday. I took out the original battery, ran it on the auto charger and then performed the repair function on the charger. I'm using the Noco Genius 5 charger [ NOCO - 5-Amp Smart Battery Charger - GENIUS5 ] which is a 5 amp charger but it has an AGM mode so I'm assuming it lowers the amps for an AGM battery. I also ordered a new volt meter so I can get a more accurate reading on the battery. The one I have now is not digital so it's hard to get a precise reading. After charging and running the repair function on the original battery I installed it back into the car and checked the voltage in the diagnostics again and it was reading 12.1V and dips down to 11.8 when I turn the head lights on. So at this point I'm pretty sure that 12v battery is bad OR there's something wrong with the control ECU that's causing it to report the wrong voltage. On wednesday with my new meter I will be able to double check the voltage on the existing battery, and can also hook up the new battery to see if I can a different result.