Help with p0a84 error?

I recently bought a 2008 prius and every once in a while the red triangle lights up and dr. prius says its throwing a p0a84 error (using a cheap BT obd2 scanner from amazon). This code indicates a problem with the battery fan. So far whenever this happens I've pulled over, checked dr. prius to make sure its not some other error, and checked the battery temps (which are nominal if a little hot, 100-110f). When it happens, if I turn off the AC and radio I can hear the fan in the back running at full blast so I know the fan itself is working fine. I've also visually inspected the fan (it's pretty clean, just a layer of dust) and the wiring harness in the rear which is prone to corrosion from a water leak. Luckily my hatch doesn't leak so far and I didn't see any corrosion in that wiring harness. But it does make me wonder what's causing the issue, and if it's safe to drive (seems fine so far). Any ideas what else to check that could be causing this issue?

I have no idea how old either battery is (the traction battery is an orange DORMAN so it's been replaced at least once) and the car only gets around 35-40 mpg. I'm prepared to replace either one but I would expect if the battery was bad I'd be getting a p0a80 error or something else. Could the 12v be causing this issue?