P0A93 on Toyota: How to Diagnose & Fix
Inverter Cooling System Performance
2 Toyota models · 2 documented issues · 2 critical · $200-$1,100 repair
P0A93 on Toyota by model: symptoms, diagnosis and fix
The Prius C has a separate cooling circuit for the power electronics (inverter/converter). The electric pump that circulates coolant through this circuit can fail, causing the inverter to overheat. When the inverter overheats, the hybrid system enters a protective shutdown mode, displaying "Hybrid System Malfunction" and severely limiting power output. The pump failure is often caused by coolant contamination or bearing wear.
Common Symptoms
- Hybrid System Malfunction warning message
- Triangle warning indicator (master caution) illuminated
- Reduced power output / vehicle feels sluggish
- No EV-only mode available
- Inverter cooling fan running at high speed constantly
How to Fix
Replace the inverter coolant pump (Toyota G9040-52010). Flush the inverter cooling circuit with distilled water then refill with Toyota Super Long Life Coolant (SLLC). Check the inverter coolant reservoir for contamination — brown or rusty fluid indicates the pump has been shedding bearing material. The pump is accessible from the engine bay and is a 1-hour repair.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota G9040-52010 inverter water pump assembly with motor
replace a confirmed failed inverter coolant pump and restore/bleed the inverter cooling loop Fitment/availability: 2012-2018 Prius C 1.5L 1NZ-FXE inverter cooling circuit; source year 2019 requires VIN confirmation because the live catal…
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Owner tips & cautions
- TipChange the inverter coolant every 100,000 miles with Toyota SLLC — most owners forget this separate cooling circuit exists
- WarningDo not ignore the Hybrid System Malfunction warning — continued driving with an overheated inverter can destroy the power electronics ($3,000+ replacement)
Sources for this issue (3)
The Highlander Hybrid uses a dedicated electric water pump to circulate coolant through the power inverter/converter, which runs separately from the engine cooling system. The electric pump wears out and stops circulating coolant, allowing the inverter and hybrid electronics to overheat. Failures often present with little warning beyond a check engine light and hybrid warning lights; if ignored, the inverter itself (a far more expensive component) can be damaged. Owners report this most on the 2006-2010 generation but it recurs across later hybrids.
Common Symptoms
- Check engine and hybrid system warning lights
- Inverter coolant leak / low inverter reservoir
- Reduced hybrid power or limp mode
- Overheating of the hybrid/inverter system
How to Fix
Replace the inverter cooling electric water pump and refill/bleed the inverter coolant loop (air-bleed procedure is required). For the 2006-2010 Highlander Hybrid the drive-motor inverter cooler water pump is Toyota PN G9040-48080 (non-tow); tow-package and later years use a different pump (e.g., G9020-48xxx family) so verify by VIN/configuration. Expect roughly $700-$1,100 done by a competent shop (pump ~$220-$290 plus diagnosis/labor and coolant). Catch it early — replacing the pump is far cheaper than an overheated inverter.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota G9040-48080 genuine drive-motor inverter cooler water pump
early-generation inverter-loop pump after flow and electrical diagnosis proves failure Fitment/availability: VIN-confirmed 2006-2010 Highlander Hybrid MHU23/MHU28 and applicable early MHU48 branch; verify production date and tow/cooling …
- Toyota G9040-47090 genuine inverter water pump assembly
middle production branch pump after inverter-loop diagnosis Fitment/availability: VIN- and production-date-confirmed 2010-2013 Highlander Hybrid branch; replaces G9040-48020 on applicable vehicles Fitment/availability: Live direct produc…
- Toyota G9040-52010 genuine inverter water pump assembly
later second-/early third-generation inverter-loop pump Fitment/availability: Production-date-confirmed 2012-2016/early-2017 Highlander Hybrid branch; reviewed catalog shows 10/2012-02/2014 and 01/2014-11/2016 applications Fitment/availa…
- Toyota G9040-52020 genuine inverter water pump assembly
late third-generation inverter-loop pump after flow and electrical testing Fitment/availability: VIN-confirmed late-2016 through 2019 Highlander Hybrid 3.5L branch; catalog production change begins 11/2016 Fitment/availability: Live dire…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (3)
P0A93 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0A93 mean on a Toyota?
P0A93 stands for "Inverter Cooling System Performance." This hybrid/electric code means the computer detected that the inverter's cooling system isn't performing well enough to keep the inverter at a safe temperature. The inverter converts high-voltage DC battery power to AC for the drive motors (and back), and it has its own dedicated liquid-cooling loop with an electric pump. When coolant flow or temperature stays out of range — meaning the inverter is overheating or at risk of it — this code sets. It commonly points to a weak inverter coolant pump or low/blocked coolant, and continuing to drive risks expensive inverter or hybrid-system damage. On Toyota it is documented across 2 models: Prius C, Highlander.
What are the most common causes of P0A93?
The most common causes of P0A93 are: Failed or weak inverter (high-voltage) coolant pump, Low coolant level or air pocket in the inverter cooling loop, Coolant leak in the hybrid cooling system, Clogged or restricted inverter cooling radiator/heat exchanger, Kinked or blocked coolant hose, Faulty coolant temperature sensor or pump wiring, Contaminated or degraded coolant. The specific cause varies by vehicle.
How much does it cost to fix P0A93 on a Toyota?
Published repair estimates on Toyota range from $200 to $1,100 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0A93 on a different make?
View P0A93 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.