Low inverter (HV) coolant or a bent or clogged inverter coolant hose (Toyota 2004 Prius manual). A failed inverter water pump or a loose pump connector (Toyota 2004 Prius manual). A failed radiator cooling fan motor or loose fan connector (Toyota 2004 Prius manual). Internal failure of the inverter assembly with converter, such as the power module (IPM) transistor, motor-generator control computer or inverter current sensor, on 2010-2015 Prius and 2012-2017 Prius V (Toyota bulletin T-SB-0003-21). A faulty hybrid control computer, hybrid transaxle, drive motor or generator, or wiring (Toyota 2004 Prius manual). On the Honda Insight: an open converter output line, an internal converter fault, or a faulty battery condition monitor module (Honda diagnostic information).

Add inverter coolant or repair a bent or clogged coolant hose (Toyota 2004 Prius manual). Replace the inverter water pump or cooling fan motor if it has failed (Toyota 2004 Prius manual). Replace the power module (IPM) transistor, motor-generator control computer, inverter current sensor or wiring inside the inverter, depending on the information code (Toyota bulletin T-SB-0003-21). Replace the whole inverter assembly with converter if it shows physical damage (Toyota bulletin T-SB-0003-21). Replace the hybrid control computer, inverter assembly or hybrid transaxle if diagnosis points there (Toyota 2004 Prius manual). On a Honda Insight, repair an open converter output line or replace the converter or battery condition monitor module (Honda diagnostic information).

P0A94🔧 Hybrid system (inverter and converter)Stop and fix promptly

P0A94: DC/DC Converter Performance (Meaning, Causes, Fixes)

Q: What does P0A94 mean?

P0A94 means a hybrid's DC/DC converter isn't working the way it should. It's best known on the Toyota Prius, where it points to the boost converter inside the inverter assembly overheating or failing, and Toyota has a service bulletin covering it on 2010-2015 Prius and 2012-2017 Prius V. Honda uses the same code on the Insight for its 12-volt charging converter. Low inverter coolant, a failed inverter water pump or cooling fan, and internal inverter failure are the main causes. Hybrids have more than one DC/DC converter, and makers use P0A94 for different ones. On Toyota hybrids, the 2004 Prius repair manual describes it as the boost converter (which raises hybrid battery voltage for the drive motors) reporting a circuit malfunction, internal short or overheating to the hybrid control computer through its fail signal line. The computer then turns on the check engine light immediately. Toyota bulletin T-SB-0003-21 says P0A94, along with P324E, P0A1A and P3004, indicates a malfunction in the inverter assembly with converter on 2010-2015 Prius and 2012-2017 Prius V. On the third-generation Honda Insight, Honda's diagnostic information applies P0A94 to the converter that charges the 12-volt battery: it sets when the 12-volt output stays 2.5 volts or more off the commanded value, stays below 11 volts for 60 seconds, or the converter reports an internal fault. RepairPal lists only the generic title, DC/DC Converter Performance.

Q: Can I keep driving with P0A94?

Stop and fix promptly. Get it checked soon. RepairPal rates P0A94 as Urgent. On Toyota hybrids it points to a fault or overheating in the boost converter inside the inverter, which powers the hybrid drive system. On the third-generation Honda Insight it means the 12-volt charging converter isn't keeping the 12-volt battery charged, so the battery will run down if you keep driving. The check engine light will also fail an emissions inspection.

Reviewed 2026-10-24 · Based on 4 cited source(s)

What P0A94 means

Hybrids have more than one DC/DC converter, and makers use P0A94 for different ones. On Toyota hybrids, the 2004 Prius repair manual describes it as the boost converter (which raises hybrid battery voltage for the drive motors) reporting a circuit malfunction, internal short or overheating to the hybrid control computer through its fail signal line. The computer then turns on the check engine light immediately. Toyota bulletin T-SB-0003-21 says P0A94, along with P324E, P0A1A and P3004, indicates a malfunction in the inverter assembly with converter on 2010-2015 Prius and 2012-2017 Prius V. On the third-generation Honda Insight, Honda's diagnostic information applies P0A94 to the converter that charges the 12-volt battery: it sets when the 12-volt output stays 2.5 volts or more off the commanded value, stays below 11 volts for 60 seconds, or the converter reports an internal fault. RepairPal lists only the generic title, DC/DC Converter Performance.

Severity: can I keep driving?

Stop and fix promptly

Get it checked soon. RepairPal rates P0A94 as Urgent. On Toyota hybrids it points to a fault or overheating in the boost converter inside the inverter, which powers the hybrid drive system. On the third-generation Honda Insight it means the 12-volt charging converter isn't keeping the 12-volt battery charged, so the battery will run down if you keep driving. The check engine light will also fail an emissions inspection.

Common symptoms

Check engine light and hybrid system warning on (Toyota manual says the light comes on immediately)
Other hybrid codes stored alongside it, such as P324E, P0A1A or P3004 (Toyota bulletin T-SB-0003-21)
Visible damage to the inverter assembly with converter (Toyota bulletin T-SB-0003-21)
On the Honda Insight, the 12 Volt Charging System light comes on instead of the check engine light, and the 12-volt battery voltage drops (Honda diagnostic information)

Likely causes

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

Low inverter (HV) coolant or a bent or clogged inverter coolant hose (Toyota 2004 Prius manual)
A failed inverter water pump or a loose pump connector (Toyota 2004 Prius manual)
A failed radiator cooling fan motor or loose fan connector (Toyota 2004 Prius manual)
Internal failure of the inverter assembly with converter, such as the power module (IPM) transistor, motor-generator control computer or inverter current sensor, on 2010-2015 Prius and 2012-2017 Prius V (Toyota bulletin T-SB-0003-21)
A faulty hybrid control computer, hybrid transaxle, drive motor or generator, or wiring (Toyota 2004 Prius manual)
On the Honda Insight: an open converter output line, an internal converter fault, or a faulty battery condition monitor module (Honda diagnostic information)

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.

Safety first: hybrids carry high voltage. Never unplug orange cables or open the inverter or hybrid battery yourself. Toyota's manual requires insulated gloves, removing the service plug and waiting at least 5 minutes before touching high-voltage parts.
Read every stored hybrid code with a scan tool that can read the hybrid system, and write down any other codes. Toyota's procedure fixes related codes such as P0A93 (inverter cooling) or motor and generator sensor codes first.
With the car off and cool, check the inverter coolant reservoir (the separate one for the hybrid system on a Prius) and top up with the coolant your owner's manual specifies if it's low.
Look for bent, pinched or leaking inverter coolant hoses.
With the car on, check whether the inverter water pump is running. Toyota's manual checks for coolant sloshing in the inverter reservoir.
Check that your Prius or Prius V model year is covered by Toyota bulletin T-SB-0003-21, and ask a Toyota dealer about hybrid warranty coverage before paying for repairs.
On a Honda Insight, check the 12-volt battery voltage. Honda's code sets if it stays under 11 volts for 60 seconds while the car is on.

Typical fixes

Add inverter coolant or repair a bent or clogged coolant hose (Toyota 2004 Prius manual)
Replace the inverter water pump or cooling fan motor if it has failed (Toyota 2004 Prius manual)
Replace the power module (IPM) transistor, motor-generator control computer, inverter current sensor or wiring inside the inverter, depending on the information code (Toyota bulletin T-SB-0003-21)
Replace the whole inverter assembly with converter if it shows physical damage (Toyota bulletin T-SB-0003-21)
Replace the hybrid control computer, inverter assembly or hybrid transaxle if diagnosis points there (Toyota 2004 Prius manual)
On a Honda Insight, repair an open converter output line or replace the converter or battery condition monitor module (Honda diagnostic information)

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

Any work on the inverter, converter or orange high-voltage cables
You need a scan tool that reads hybrid codes and Toyota information codes (Toyota Techstream or equivalent)
Your Prius may be covered by Toyota bulletin T-SB-0003-21 and the Toyota hybrid system warranty, so check with a dealer first
The car won't go into READY mode or loses power

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 P0A94 serious?

Yes. RepairPal rates it Urgent. On a Toyota it points to a fault or overheating in the boost converter inside the inverter, which can be expensive if ignored. Start with the cheap checks (inverter coolant level and the inverter water pump) and get it diagnosed soon.

Is there a Toyota service bulletin for P0A94?

Yes. T-SB-0003-21 (revised February 2023) covers 2010-2015 Prius and 2012-2017 Prius V with P0A94, P324E, P0A1A and/or P3004. It has the dealer replace the inverter assembly if it's physically damaged, or specific parts inside it based on the information code. Toyota says the repair is covered under the Toyota hybrid system warranty of 8 years or 100,000 miles, with longer emissions coverage for some California-certified Prius models.

Can low inverter coolant cause P0A94?

Yes, on a Toyota. The 2004 Prius repair manual describes P0A94 as boost converter overheating, and its first checks are the inverter coolant level, the coolant hoses, the inverter water pump and the cooling fans.

Do the sources agree on P0A94?

Not fully, because makers use the code for different converters. Toyota uses it for the boost converter inside the inverter, which feeds the hybrid drive system. Honda uses it on the Insight for the converter that charges the 12-volt battery, and on the Honda it turns on the 12 Volt Charging System light rather than the check engine light. RepairPal gives only the generic title. Toyota's 2004 manual focuses on overheating and cooling-system causes, while Toyota's later bulletin for 2010-2017 models focuses on internal inverter parts.

How much does it cost to fix P0A94?

None of the sources give a repair cost. It ranges from topping up inverter coolant to replacing a water pump or the whole inverter. On covered Prius and Prius V models, ask a Toyota dealer about bulletin T-SB-0003-21 and hybrid warranty coverage first.

Sources

Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.