fault code guideHybrid & EV
P0A93: Inverter Cooling System Performance (Hybrid)
Your hybrid system has detected that its separate inverter cooling system is not working properly. Continuing to drive can cause the high-voltage inverter to overheat and fail completely.
How it shows up: You will usually see a Check Hybrid System warning or a master triangle warning alongside the steady amber engine management light. The car may enter limp mode with noticeably reduced power, and the specific P0A93 code is confirmed using an OBD scanner.
Updated 9 November 2026
Can I keep driving?
Stop driving
Stop driving as soon as it is safe, because driving with a hot inverter can destroy the component and cause thousands of pounds or euro in damage.
What to do right now
- 1Pull over smoothly in a safe place, switch the car completely off and leave it parked.
- 2Do not touch any orange high-voltage cables under the bonnet, as high-voltage components are dangerous and strictly for trained technicians only.
- 3Allow the engine bay to cool down fully before lifting the bonnet to inspect fluid levels.
- 4Arrange for roadside assistance to recover the car to a qualified garage rather than driving further.
Likely causes
Most likely first.
- Likely
Failed electric inverter water pump
Hybrid cars use a dedicated 12-volt electric coolant pump for the inverter that runs continuously while the car is on. When this pump motor burns out or seizes, coolant stops circulating and the inverter quickly overheats.
- Possible
Low inverter coolant level
A leak from an inverter hose, a cracked expansion tank or a stone strike to the dedicated inverter radiator allows coolant to escape. Without enough fluid to carry heat away, temperatures rise beyond safe limits.
- Possible
Air trapped in the inverter cooling loop
If the hybrid cooling system was recently serviced or refilled without being bled correctly, air pockets prevent coolant from flowing through the inverter jacket.
- Rare
Blocked inverter radiator or wiring fault
Road debris blocking airflow through the hybrid radiator or a broken power supply wire to the coolant pump stops normal heat dissipation.
What you can check yourself
Park somewhere safe and level, engine off, before you start.
- 1
Check the inverter expansion tank level
Wait until the car is stone cold. Hybrids have two separate coolant tanks under the bonnet; locate the smaller inverter reservoir and verify that the pink or blue fluid sits between the minimum and maximum lines. Never touch any orange wiring near the reservoir.
- 2
Look for visible coolant circulation
With the car completely cold, turn the car on so the dashboard displays ready mode, but keep the gearbox in park. Look through the translucent plastic of the inverter coolant tank without removing the cap, or remove the cap only if the system is cold, to see if the fluid surface is churning. If the fluid sits perfectly flat and still, the pump has stopped working.
- 3
Inspect the ground and hoses for pink or blue residue
Look under the front bumper and beneath the engine bay for drips or dried crusty coolant deposits. Wet patches or crusty stains indicate an external leak in the radiator, pump or connecting hoses.
- 4
Verify no orange cables are disturbed
Look only from a safe distance and ensure you never touch or pull any high-voltage orange cables. Work on high-voltage components is strictly for qualified technicians with insulated safety gear.
Rough cost to fix
Rough estimateTypical prices in Ireland (€) and the UK (£), from an independent garage up to a main dealer. Prices depend mainly on whether the fault was caught before the heat ruined the high-voltage inverter itself.
Replace electric inverter coolant pump and bleed system
- Do it yourself
- Garage job
- At a garage
- €280–550£240–480 in the UK
Inverter cooling leak repair or hose replacement
- Do it yourself
- Garage job
- At a garage
- €140–320£120–280 in the UK
Complete hybrid inverter assembly replacement
- Do it yourself
- Garage job
- At a garage
- €1,200–2,900£1,050–2,500 in the UK
When to go to a garage
- The inverter coolant tank shows no fluid movement when the car is switched to ready mode.
- The dashboard displays a red master warning triangle or Check Hybrid System alongside reduced vehicle power.
- The inverter expansion tank is completely dry or you spot a coolant leak near hybrid components.
- Any high-voltage warning appears, because all high-voltage orange-cabled parts require trained technicians.
Questions drivers ask
Can I drive to a garage with code P0A93 showing?
No, you should not drive the car. Without active coolant flow, the hybrid inverter can reach destructive temperatures within several minutes of driving. It is far cheaper to pay for roadside recovery than to replace a burnt-out inverter assembly.
Can I replace the inverter coolant pump myself at home?
DIY replacement is not recommended for ordinary drivers. While the pump itself runs on 12 volts, it sits directly adjacent to dangerous high-voltage orange cabling and the system requires a specialised bleeding procedure to remove trapped air locks safely.
Will clearing code P0A93 turn the warning off permanently?
No, clearing the code will not fix the mechanical or electrical failure. As soon as the hybrid computer monitors the coolant temperature rise or lack of pump circuit feedback again, the code and warnings will return immediately.
Will fault code P0A93 cause an MOT or NCT failure?
On the UK MOT, an illuminated engine management light is an automatic fail for petrol cars first used from July 2003. On the Irish NCT, an engine warning light alone yields an advisory pass, but the car will fail if a severe hybrid fault or limp mode stops the test being completed.
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.