Inverter Coolant Pump Speed Signal

2015 Prius Three with ~ 60,000 miles, no accident, first owner, original aux battery.

Hey guys,

Going to need some help. Woke up one morning and the car didn't start. No interior lights, headlights or anything. Pressing the igniton once and twice without depressing the brake pedal and nothing lit up. Figured it was the battery so I charged it up and then it started and parked the car into the garage and let it charge.

Fast foward to that evening, I checked the voltage of the battery and it looked fine 12.5ish, started (ready) the car to see if it would work and it did. Turned it off and I heard a weird sound coming from the engine bay, not your typical pumping sounds or whatever. It was more of a clicking near where the ECU/inverter coolant reservoir and inverter was. Then I quickly noticed the voltage of the battey was rapidly decreasing.

Tried removing all of the fuses one by one and nothing would stop it until I removed either the 7.5a AM2 or the 7.5a ABS Main No.2 fuse or a weird combination of both and it stopped the weird clicking/whirring sound or my battery just got too low. Charged up the battery to full and it was able to start (Ready) but I got a DTC code from my OBD2 sensor. It had 3-4 warnings of the same code.

The code was: DTC P314A

Cleared it and it still had a permanent code. Googled it and apparently it's for the Inverter Coolant Pump Speed Signal?

When I started the car (Ready), one of the rad fans kicked on so I was guessing it was the pump that had failed. Tried looking inside the reservoir with the 2x start without pressing the brake pedal and didn't see any movement.



Fast forward to today, I replaced the pump and lost some fluid in the mean time. Filled the reservoir back up and turned the car on (Ready), it started and the pump sucked the fluid in so I'm guessing the new pump works. Car didn't show any codes with the start button pressed 2x aswell as in Ready mode but then I turned the car off and then it still had the whirring/clicking sound that rapidly drained the battery and I was unable to start the car again, same thing no lights or anything from the screen when I keep pressing the start button or any combination probably due to the low battery. Not sure if the code is back on since the battery is charging right now..

What would be causing this? Would it be a dying AUX battery? I charged it up and I checked the voltage with multimeter and it didnt really lose anything over night, car starts fine when it's fully charged. I believe the voltage is around 14ish or something I forget when the car is ready so it is being charged.

Just that turning it off = RIP battery... due to something clicking/whirring sounds like its coming from behind the inverter coolant reservoir or under it? Fuses look fine. I am missing one 10a fuse that states MAYDAY but I doubt that does anything.

EDIT: Apparently the battery even when fully charged doesn't start up anymore. I open the driver side door and it makes the sound and the voltage on the battery starts dropping quickly. Still nothing when I press the start button.

 

Yeah probably the route I'm going to go next. Voltage drops way too irratically and fast when I charge it and then open the door and the weird sound happens and then I can't even get anything to go on.

 

Do you have any recommendations for a replacement battery? They're pretty pricey from a quick search on AutoZone, around 238 for the Optima and $195 for the Duralast...