P0A93: How to Diagnose & Fix — Inverter Cooling System Performance
4 vehicles · 2 makes · $200-$1,200 repair
How to diagnose and fix P0A93: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Lexus CT · 2011–2017
The electric water pump on the CT200h hybrid system fails prematurely, causing coolant circulation loss for the hybrid inverter and electric motor. Unlike conventional belt-driven water pumps, this is an electric unit that controls coolant flow to the high-voltage hybrid components. Failure can lead to hybrid system overheating and shutdown.
Common Symptoms
- Hybrid system warning light
- Reduced power mode activated
- Engine temperature warning
- Coolant leak from electric pump area
- Hybrid system shuts down in hot weather
How to Fix
Replace the electric water pump assembly. Use the OEM Toyota/Lexus part for the hybrid cooling circuit. After replacement, bleed the hybrid cooling system thoroughly to remove air pockets. Check the coolant level in both the engine and hybrid cooling circuits.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- G9040-47090 genuine Lexus inverter water pumpOEMG9040-47090
Replace a confirmed failed early inverter coolant pump Fitment/availability: Live page lists 2011-2013 CT200h 2ZR-FXE and identifies G9040-47090 as replacing G9040-48020. The overlap with the later pump requires VIN/production-date confi…
- G9040-52010 genuine Lexus inverter water pumpOEMG9040-52010
Replace a confirmed failed later inverter coolant pump Fitment/availability: Live page lists 2012-2017 CT200h 2ZR-FXE. For 2012-2013, confirm VIN/production date because the early listing overlaps.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipThe CT200h has TWO separate cooling systems — one for the engine and one for the hybrid components. Make sure both are maintained with fresh coolant at the recommended intervals.
Toyota Prius C · 2012–2019
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…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
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)
Lexus GS · 2007–2011
The GS 450h carries a second, completely separate cooling circuit for the power inverter, consisting of an electric water pump, its own radiator and a fan. That electric pump fails - it is a known wear item on the S190 hybrid - and when circulation stops the inverter overheats. The car sets P0A93 (inverter cooling system performance), lights the master warning and hybrid system warning, and typically drops into a limited-power limp mode or refuses to enter READY. Because the inverter is a five-figure component, a failed $200-$500 pump that is left unaddressed is the cheap failure that causes the expensive one. Low inverter coolant level in the dedicated reservoir produces the same code and should be checked first. This is exclusive to the GS 450h - the GS 350, GS 430 and GS 460 have no inverter circuit.
Common Symptoms
- Check hybrid system warning message
- Master warning light and red triangle
- Reduced power / limp mode
- Vehicle will not enter READY
- Inverter coolant reservoir low or not circulating
How to Fix
Verify the inverter coolant reservoir level and bleed the circuit first; air trapped after a coolant service alone can set P0A93. If level and bleed are correct, replace the inverter electric water pump (a separate part from the engine water pump) and refill with Toyota Super Long Life coolant, then bleed the inverter circuit per the factory procedure - improper bleeding will re-set the code. Parts run roughly $200-$500 with total shop cost commonly $400-$900. Do not continue driving with the hybrid warning lit.
Sources for this issue (3)
Toyota Highlander · 2006–2019
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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?
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.
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?
Repair costs for P0A93 range from $200 to $1,200, depending on the vehicle and root cause.
Which vehicles are affected by P0A93?
Au7o has documented P0A93 across 4 vehicle models from 2 manufacturers: Lexus, Toyota.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.