P0A93🔧 Hybrid system (inverter cooling)Stop and fix promptly

P0A93: Inverter Cooling System Performance (Meaning, Causes, Fixes)

Reviewed 2026-10-22 · Based on 3 cited source(s)

What P0A93 means

Hybrid vehicles use an inverter to turn the high-voltage direct current from the hybrid battery into alternating current for the electric motor-generators. Toyota's 2004 Prius repair manual says the inverter generates heat during that conversion, so it has its own cooling system with an electric water pump, a cooling fan and a radiator, independent of the engine cooling system. The hybrid control computer watches that pump, fan and cooling loop continuously and turns on the check engine light immediately when it finds a fault. RepairPal describes P0A93 the same way: the high-voltage control module detects a problem with the inverter's cooling system and tells the engine computer to set the code. On a Prius, Toyota adds an information code that narrows it down: 346 points to the water pump side and 347 points to the electric cooling fan side.

Severity: can I keep driving?

Stop and fix promptly

Treat this as urgent. RepairPal rates P0A93 Urgent and says the high-voltage system may overheat. Toyota's Prius repair manual explains that the inverter makes heat while it converts battery power for the electric motors, and that heat could damage the inverter if its cooling system isn't working. Get it diagnosed promptly and avoid long or hard drives until then. The inverter and its orange cables carry dangerous high voltage: do not open the inverter or touch those cables yourself.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Low inverter (HV) coolant or a leak in the hybrid cooling system (Toyota repair manual, RepairPal)
  2. A failed or slow electric inverter water pump (Toyota repair manual, RepairPal). On 2004 to certain 2007 Prius, Toyota says air trapped at the pump bearing could make it run slowly (NHTSA recall 12V-536, which refers to the earlier Toyota campaign)
  3. A water pump with a corroded or broken motor coil wire on 2004-2009 Prius (NHTSA recall 12V-536)
  4. Bent or clogged cooling hoses (Toyota repair manual)
  5. A loose or poorly connected water pump or cooling fan connector, or damaged wiring (Toyota repair manual)
  6. A faulty cooling fan motor (Toyota repair manual)
  7. A faulty inverter / converter assembly, which Toyota's procedure checks last (Toyota repair manual)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Read all stored codes and, if your scan tool shows it, the information code. On a Prius, 346 points to the water pump and 347 points to the cooling fan (Toyota repair manual).
  2. With the car off and cool, check the inverter coolant reservoir level. It is a separate reservoir from the engine coolant on a Prius; check your owner's manual to find it. Toyota's first step is checking for enough inverter coolant.
  3. Look for coolant leaks and bent or kinked hoses in the inverter cooling loop (Toyota repair manual).
  4. With the power switch on (ready not required), look in the inverter coolant reservoir. Toyota's test for a working pump is that the coolant visibly sloshes or moves in the reservoir tank.
  5. Check whether your vehicle has an open recall by entering the VIN at nhtsa.gov/recalls. 2004-2009 Prius are covered by recall 12V-536 for the inverter water pump.
  6. Do not open the inverter or touch orange high-voltage cables.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • You have a hybrid warning light, reduced power, or the car won't go into ready mode
  • The coolant level and hoses look fine but the code keeps coming back
  • The inverter water pump or cooling fans need testing or replacement; refilling the inverter coolant may also need the air bled out of the system, and Toyota says trapped air is what made early Prius pumps run slowly
  • Your vehicle may be covered by a recall; a Toyota dealer can check and do recall repairs free

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P0A93 serious?

Yes. RepairPal rates it Urgent and says the high-voltage system may overheat. Toyota's manual says the inverter can be damaged by heat if its cooling system isn't working, and Toyota's recall report says a failed pump can in some cases shut down the hybrid system while driving.

Is the inverter coolant the same as the engine coolant?

On a Prius, the inverter has its own cooling system with its own pump, radiator and reservoir, separate from the engine cooling system, according to Toyota's repair manual. Check your owner's manual for the correct coolant and fill point.

Is P0A93 covered by a recall?

On 2004-2009 Toyota Prius, Toyota recalled the hybrid water pump (NHTSA recall 12V-536) because its motor coil wire could corrode and break. Earlier, Toyota ran a campaign for 2004 to certain 2007 Prius pumps that could run slowly from trapped air. Check your VIN at nhtsa.gov/recalls.

Do sources disagree on P0A93?

They mostly agree it is an inverter cooling problem. RepairPal lists only two causes, a coolant leak and a failed high-voltage coolant pump. Toyota's manual also lists cooling fans, bent hoses, wiring and connectors, and the inverter assembly itself.

How much does it cost to fix P0A93?

None of the sources give a repair cost. It can be anything from topping up coolant or fixing a connector to replacing the water pump, a fan, or the inverter, and recall repairs on affected Prius are free, so get a diagnosis and check recalls first.

Sources

  1. RepairPal: P0A93 Inverter "A" Cooling System Performance (rated Urgent)
  2. Toyota 2004 Prius repair manual (RM1075U): DTC P0A93/346 and P0A93/347 Inverter Cooling System Performance
  3. NHTSA recall 12V-536: Toyota Part 573 report, 2004-2009 Prius hybrid water pump

Last reviewed 2026-10-22. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.