P0A93 means the Prius hybrid inverter has its own dedicated coolant loop and the car has decided that loop is not moving enough heat away from the power electronics. On the 2010–2015 Prius the usual culprit is the electric inverter coolant pump failing or an air pocket left in the loop after a coolant service — not the main engine cooling system. It is worth taking seriously because the inverter/IPM assembly it protects is the same one behind several Toyota recalls.
What the real-world data shows
Related NHTSA recalls (the power-electronics assembly this code protects):
- 14V053000 — Hybrid propulsion system: inverter. Toyota recall of certain 2010–2014 Prius for an inverter (IPM) fault that can cause the hybrid system to shut down — the power-electronics assembly the P0A93 cooling loop is meant to keep cool.
- 20V369000 — Hybrid propulsion system: inverter. Toyota recall of certain 2013–2015 Prius / Prius-family vehicles for an inverter concern in the same assembly.
- 18V684000 — Hybrid propulsion system. Toyota recall of certain 2010–2014 Prius covering the hybrid propulsion system.
Owner complaints: In NHTSA’s complaint database the inverter/coolant theme is heavily concentrated in the Gen-3 Prius: of 2,822 complaints filed for the 2010 Prius, 74 mention the inverter, coolant or water pump; the 2012 Prius shows 32 such mentions of 687, and the 2013 Prius 17 of 410 (pulled 2026-10-04). The pattern thins out sharply on the Gen-4 (2016+) cars.
How often this is searched: “2024 Toyota Prius P0A93” is the single most-searched make/model DTC query in our own Bing Webmaster logs (~500 impressions/month), which is why we built this page first.
Common causes on the Toyota Prius
- Failed electric inverter coolant pump (the small second water pump that circulates coolant only through the inverter/power-electronics loop) — the most common cause on this generation
- Air pocket trapped in the inverter coolant loop after an engine- or inverter-coolant service that was not bled correctly
- Low inverter coolant level or old, degraded Toyota Super Long Life Coolant in the inverter reservoir
- Restricted or kinked inverter coolant hose, or a clogged inverter cooler/radiator passage
- Faulty inverter coolant temperature sensor reporting a false performance fault
How to diagnose it
- Confirm which coolant loop and check its level — The Prius has two separate coolant systems; P0A93 is the inverter (power-electronics) loop, which has its own reservoir. Check that reservoir cold — a low or empty inverter reservoir points straight at a leak, a bad pump, or an air lock, not the engine cooling system.
- Verify the inverter coolant pump is actually running — With the car in READY, look/listen for coolant movement in the inverter reservoir. No visible flow with a full reservoir is the classic failed-pump signature on the 2010–2015 cars. The pump can also be checked for current draw.
- Read inverter coolant temperature in live data — A capable scan tool shows the inverter coolant temperature PID. A reading that climbs abnormally under load while the engine temperature stays normal confirms the fault is isolated to the inverter loop.
- Bleed air from the inverter loop — If P0A93 appeared right after a coolant service, an air pocket is likely. Follow the Prius inverter-loop bleed procedure before condemning parts — many cases clear here.
- Replace the inverter coolant pump if there is no flow — If the reservoir is full, there is no air, and the pump still will not move coolant, replace the electric inverter water pump and re-bleed. Clear the code and confirm the inverter temperature stabilises under load.
What the fix costs
Typical range: $250–$650 (US). Typical US range for an electric inverter coolant pump replacement: roughly $130–300 for the pump plus about $120–350 labour including the bleed. An air-lock-only fix (no parts) is far cheaper; coolant-system damage that has already stressed the inverter is far more.
FAQ
Is P0A93 the same as the engine overheating?
No. The Prius keeps the inverter/power-electronics on a separate coolant loop from the petrol engine. P0A93 is specifically about that inverter loop underperforming, so the engine temperature gauge can look completely normal while this code is stored.
Can I keep driving with P0A93?
Treat it as limp-it-home, not ignore-it. The code means the assembly that runs the car’s high-voltage power electronics may be running hotter than designed. Short, gentle driving to get it looked at is reasonable; sustained high-load driving risks heat-stressing an expensive inverter.
Could this be covered by a Toyota recall?
Possibly worth checking. Toyota issued several recalls on the 2010–2015 Prius inverter/hybrid system (NHTSA 14V053000, 20V369000, 18V684000). Those address inverter failures rather than the cooling code itself, but if your VIN is affected the dealer repair may be free — enter your VIN on NHTSA’s recall lookup.
Why did P0A93 appear right after a coolant change?
Because the inverter loop is easy to leave air in. A trapped air pocket stops the small electric pump moving heat, and the car reads that as a performance fault. Properly bleeding the inverter loop clears many post-service cases with no parts needed.
How we researched this
Recall and complaint figures were retrieved on 2026-10-04 from NHTSA’s public recalls and complaints APIs for the Toyota Prius by model year, and filtered to inverter/coolant/water-pump mentions. Search-demand figures come from our own Bing Webmaster Tools data for autodtcs.com. Diagnostic steps and cost ranges are restated general service facts, not reproduced from any single proprietary manual.
Sources: NHTSA recalls API (Toyota Prius, by model year); NHTSA complaints database (Toyota Prius); AutoDTCs first-party Bing Webmaster search-demand logs
Last updated 2026-10-04.