2008 Prius No READY + Red Triangle + No Inverter Coolant Flow

I’m having a no-start / no READY issue with my 2008 Prius and I’m trying to confirm the root cause before replacing parts.

Here’s everything that’s happened:

The car originally would start (go into READY), run briefly, then shut off with a red triangle and “PROBLEM” message. After that, it got worse and now it won’t go into READY at all. It powers on like normal (dash lights, etc.) and sounds like it’s about to start, but “READY” never appears.

I replaced the 12V battery with a new one, and all connections are tight and clean. Brake lights work, so the brake switch seems fine. I also checked the main fusible link and basic fuses—they appear good.

I pulled codes with a basic scanner and got a bunch of seemingly unrelated codes (MAF, throttle, O2, lean condition, etc.), which made me suspect a voltage or system issue rather than all those parts failing at once.

Here’s the key observation:
When I was able to get the car to start briefly, I checked the inverter coolant reservoir and saw NO movement at all—only slight vibration from the engine. I also put my hand on the inverter coolant pump and only felt a brief vibration at startup, then nothing. No steady humming.

From what I understand, the inverter coolant should be visibly circulating when the car is in READY, even if the engine isn’t running. Mine is completely still.

Now the car won’t go into READY anymore at all (just powers on but doesn’t start), and I still have the red triangle.

Based on this, I’m suspecting a failed inverter coolant pump causing inverter overheating and a hybrid system lockout.

Before I replace the pump, I just want to confirm:

- Does this sound consistent with inverter coolant pump failure?
- Would a failed pump cause the car to eventually refuse to go into READY at all?
- Is there anything else I should check (wiring, fuse, etc.) before replacing it?

Appreciate any help—trying not to throw parts at it blindly.