P0A93 / Weird pump behavior

2006 Prius 183k miles

During a recent longish drive (about 1 hour of highway driving in, in 80F weather), the red triangle of death came on along with the check engine light. Turned out to be P0A93 (inverter cooling system performance). I then checked the inverter pump operation by looking for turbulence in the inverter overfill tank. There was some turbulence but not as much as what I've seen in others' YT videos. Given that the pump was "working" (to some extent), I reset the light and code by unplugging and replugging the 12V battery and continued on with my trip home without any further codes. On another trip while going up a big hill, the lights and codes came on again. Seems to me that these instances are indicating inverter overheating, hence the delayed errors.

I scoured PRIUSchat's many many posts on this topic for several hours and made a list of things that could have gone wrong that I checked one by one. Here are the things that I checked that did not have any issues:

• inverter overfill coolant tank level is good
• radiator coolant level good
• no debris at bottom of radiator
• checked hose routing according to the inverter coolant line schematic and all is good (no swapped hoses)
• no visible coolant leaks on hoses or pump housing
• all fuses (especially AM2) passed continuity tests
• bled the system with vinyl hose method for several minutes, only the tiniest air bubbles came out in the first 10 seconds of bleeding nothing else, pretty air free as far as I can tell
• no visible coolant contaminants
• both radiator fans spin and blow air towards the engine when AC is on coldest

Now we get to the interesting part. Of course, one of the things to check is for any corrosion on the pump connector. Before this point, the pump had always turned on when the car was in Ready or in accessory mode. I could always hear a very quite, consistent hum, and feel a vibration when touching the pump or the 2 hoses. As mentioned, the turbulence in the tank had always been very gentle compared to the videos I saw. Upon unplugging the pump and checking the plug on both sides, there was no visible corrosion, they were spotless. When I plugged the connector back in and turned the car on, I get nothing from the pump. Completely quiet, no vibration, no turbulence in the tank. I'm 99.9% sure I plugged it in correctly and confirmed hearing and feeling it click in.

I'm kind of stuck now and would love to get your input on what to do next. I have service records going back about 30-40k miles and in that time, the pump was never replaced, and the coolant was never drained. I did notice that the pump had the silver bracket as opposed to the black bracket, so maybe it was replaced under the recall many years ago. Not sure. Also a few other components were replaced aftermarket by previous owners / mechanics, I wouldn't be surprised if this is also the case with this pump.

Should I just try replacing the pump or is there anything else I could be troubleshooting? I was thinking maybe I should try getting the ENF code with Techstream but not sure if that'll actually be worth the effort to set it up.

All feedback and insights welcome! Thanks y'all!!

 

Ok yea I will place an order for an OEM pump. When replacing the pump should I also drain the coolant and replace it with new coolant? I'm more inclined to do so given that it hasn't been changed in at least 40k miles potentially a lot more. But I'm worried about air trapment when turning on the new pump for the first time, not sure if that could cause damage to the new pump.