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P0A94

fault code guideHybrid & EV

P0A94: DC/DC (Boost) Converter Performance (Hybrid)

This code means the hybrid boost converter inside the inverter is malfunctioning or overheating. Your car may shut down unexpectedly, lose power, or refuse to enter READY mode.

How it shows up: The engine management light, master warning triangle, and a Check Hybrid System message will appear on the dashboard, accompanied by limp mode or sudden loss of drive. A technician or driver reads the P0A94 code using an OBD diagnostic scanner.

Updated 9 November 2026

Can I keep driving?

Stop driving

Stop driving because the hybrid system can shut down without warning, leaving you stranded without motive power in moving traffic.

What to do right now

  1. 1Pull over safely to the side of the road or a car park away from moving traffic.
  2. 2Turn off the ignition completely and switch on your hazard warning lights.
  3. 3Do not attempt to open hybrid inverter casings or touch any orange high-voltage cables under the bonnet.
  4. 4Arrange for roadside assistance to tow the vehicle to a qualified hybrid specialist garage.

Likely causes

Most likely first.

  1. Likely

    Failed hybrid boost converter

    Internal switching transistors within the boost converter module fail under electrical or thermal stress. This breaks the high-voltage circuit needed to step up battery voltage for the electric drive motors.

  2. Possible

    Inverter cooling system failure

    A failed electric inverter water pump stops coolant circulating around the power electronics. Extreme heat causes the converter to malfunction and forces the computer to cut power to prevent a fire.

  3. Possible

    Low or aerated inverter coolant

    Leaks or air pockets inside the dedicated hybrid cooling loop lower heat transfer efficiency. The boost converter overheats rapidly under acceleration and logs this fault code.

  4. Rare

    Internal capacitor or circuit board degradation

    Solder joints, internal wiring, or power capacitors degrade with vehicle age and heat cycles. This creates severe electrical resistance or short circuits inside the inverter housing.

What you can check yourself

Park somewhere safe and level, engine off, before you start.

  1. 1

    Check the inverter coolant level

    Park on level ground, ensure the engine is cool, and look at the clear plastic hybrid coolant expansion tank under the bonnet. The fluid level should sit comfortably between the MIN and MAX lines without removing the pressurised cap.

  2. 2

    Observe inverter coolant circulation

    Turn the ignition to the ON position without starting the engine, and look through the side of the hybrid reservoir for swirling fluid movement. A calm, still pool suggests the dedicated electric inverter water pump has stopped running.

  3. 3

    Inspect the ground for fluid leaks

    Look under the front bumper and undertrays for puddles of pink or blue hybrid coolant. Never touch orange cables or high-voltage components; high-voltage (orange-cabled) parts are for trained technicians only.

  4. 4

    Test the 12-volt auxiliary battery

    Check the terminal voltage of the standard 12-volt battery in the boot or engine bay with a digital multimeter. A weak battery reading below 12.0 volts at rest can corrupt computer sensor readings and trigger false hybrid codes.

Rough cost to fix

Rough estimate

Typical prices in Ireland (€) and the UK (£), from an independent garage up to a main dealer. Costs depend heavily on whether the problem is an external cooling pump failure or an internal transistor burnout requiring a replacement inverter unit.

  • Inverter electric coolant pump replacement

    Do it yourself
    Garage job
    At a garage
    €320–650£280–580 in the UK

  • Reconditioned hybrid inverter assembly replacement

    Do it yourself
    Garage job
    At a garage
    €950–1,900£850–1,650 in the UK

  • New genuine hybrid inverter and converter replacement

    Do it yourself
    Garage job
    At a garage
    €2,500–4,500£2,200–3,900 in the UK

When to go to a garage

  • Call roadside assistance immediately if the car drops into limp mode or fails to show the READY light on the dashboard.
  • Seek professional help if the inverter coolant reservoir is empty or shows no fluid movement when the ignition is switched on.
  • Consult a qualified hybrid specialist as soon as fault code P0A94 appears alongside companion code P0A93.

Questions drivers ask

Can I drive my car with fault code P0A94 showing?

No, you should not drive the car with this fault code active. The hybrid system will often cut power completely without warning to protect components from permanent heat damage or electrical fire. Driving in this condition creates a serious accident risk if the powertrain shuts down on a busy road or motorway.

Will clearing the code allow me to drive home?

Clearing the code with a handheld scanner will not fix damaged electronics or a failed cooling pump. Even if the car allows you to select drive immediately after a reset, the fault will reoccur within seconds as soon as the boost converter draws electrical load. Continuing to reset the code can cause irreparable damage to healthy hybrid components.

How does code P0A94 differ from code P0A93?

Code P0A93 flags an issue with the physical cooling system of the inverter, such as a dead water pump or blocked radiator. Code P0A94 indicates an electrical performance problem within the boost converter circuit itself. However, prolonged driving with code P0A93 often causes severe overheating that triggers code P0A94.

Will fault code P0A94 cause an NCT or MOT failure?

Yes, on an MOT in the UK, an illuminated engine management light is an automatic failure. On the Irish NCT, while hybrid electrical codes alone do not automatically fail the test, the car will fail if warning lights signal powertrain failure or if the vehicle cannot start and drive safely onto the test equipment.

Test rules here are for the National Car Test in Ireland (NCT) and the MOT in the UK. Elsewhere, check the regulations of your own country or state before going for a vehicle test.

The warning light you may see

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General guidance for most cars, not a diagnosis of yours. Details differ by make, model and year - check your handbook, and if in doubt, don't drive.