Can you drive with the hybrid system warning light on?

Usually yes, as far as a garage, provided the lamp is amber, nothing red is lit alongside it and the car is driving normally. The hybrid controller has logged a fault and will often keep the car running on the petrol engine while it does so. Stop and call for help if a red warning appears, if the car loses power, or if you smell anything hot or acrid.

Do hybrid cars need an MOT and an emissions test?

Yes to both. Hybrids follow the same MOT schedule as everything else, and because they have a petrol engine and an exhaust they take the full emissions test — the exemption people have heard about applies only to battery-electric and hydrogen fuel cell cars. Hybrids first used on or after 1 July 2003 are also failed if the engine malfunction indicator lamp is illuminated, exactly as a conventional petrol car would be.

What is the difference between the hybrid system light and the engine light?

They report to different bosses. The engine management lamp is the emissions-related malfunction indicator required by law and is set by the engine control unit. The hybrid system lamp is manufacturer-specific and covers the electric side: the motor-generators, inverter, converter and traction battery. A fault can light one, the other, or both, and only the engine lamp is an automatic MOT failure. If both are lit, read the codes from the hybrid modules as well as the engine, because a basic code reader only sees half the picture.

Can a flat 12-volt battery cause hybrid warning lights?

Very often, and it is the first thing worth eliminating. Hybrids and EVs still run all their control units, contactors and network communication from a conventional 12-volt battery, and when it weakens the modules brown out and start reporting each other as missing. The result is a dashboard full of unrelated warnings — hybrid system, ABS, stability control, parking brake — that all clear the moment a healthy battery goes in. A battery test costs very little and can save an expensive diagnostic.

Dashboard warning light

Hybrid system warning light

Last updated 27 July 2026

Quick answer

The hybrid control system has logged a fault somewhere across the petrol engine, the motor-generators, the inverter, the converter or the traction battery. The car will often still drive, sometimes only on the engine and sometimes with reduced power, but it needs the codes read rather than a guess.

What to do: Get it checked within days
Can you drive?: Only to a garage

Why it is amber

A system has reported a malfunction, or something needs attention. The car is usually still driveable, but the fault will not clear itself and several amber lamps are an automatic MOT failure.

What turns it on

A hybrid runs several control units in conversation with each other over the vehicle network — engine, hybrid control, battery management, inverter. When any of them reports a value outside range, or simply stops answering, the hybrid controller stores a code and lights this lamp. On most cars it is accompanied by a message and, if the fault touches emissions, by the engine management lamp as well.

What to do about it

Note whether anything else is lit alongside it, particularly the engine management lamp or a red high-voltage warning. A red lamp in company changes the answer from drive carefully to stop.
Pull over somewhere safe, switch the car fully off, wait a minute and restart. A genuine fault comes straight back; a transient network glitch often does not.
Get the codes read, and use a tool that reads the hybrid and battery modules rather than just the engine. A basic code reader talks only to the engine controller and will report nothing at all on a fault that lives in the battery management system.
Have the 12-volt battery tested early. It is cheap to check, and a tired 12-volt battery on a hybrid produces a spread of unrelated-looking warnings that all disappear when it is replaced.
If the car has dropped into reduced power, keep off fast roads. A hybrid that cannot use its electric motor may struggle to hold motorway speed on the engine alone.

Can you keep driving?

Only to a garage

An amber hybrid system lamp on its own, with the car driving normally, is not an emergency and you can get it to a garage. Treat two things as exceptions. If a red warning is lit alongside it, stop. And if the car has lost power or is refusing to use the electric motor, get off fast roads, because a hybrid running on a small petrol engine alone is slower than the traffic around it expects.

What causes it

A weak or failing 12-volt battery, which is the first thing to rule out and the cause a surprising number of these turn out to be
Traction battery degradation, typically one weak cell block dragging the pack out of balance on a high-mileage car
A failed traction battery cooling fan or a blocked cooling intake, which on many hybrids sits under a rear seat and fills with dust and pet hair
An inverter or converter fault, which is the serious and expensive end
A failing motor-generator position sensor or temperature sensor
A communication fault between control units, often from corroded connectors or a chafed loom
An ordinary engine fault on the petrol side, which the hybrid controller reports because it can no longer run the engine as it wants to

Does it fail an MOT?

Not on its own — but what causes it often does.

The hybrid system lamp is not a listed defect and no part of the test examines the hybrid drivetrain. What catches people out is the engine side: a full or plug-in hybrid with a petrol engine takes the same emissions test as any petrol car and falls under the same rule on the engine malfunction indicator lamp, which is a major defect on cars first used on or after 1 July 2003. Only battery-electric cars skip the tailpipe test. So if the hybrid fault has also lit the engine management lamp, the car fails, and the hybrid lamp is simply the messenger that told you first.

Fault codes that turn this light on

The lamp tells you which system reported a problem. The code stored behind it names the check that failed, which is the difference between knowing something is wrong and knowing where to look. These are the ones that commonly sit behind this symbol.

P0A0FHybrid Engine Failed to Start
P0A7FHybrid Battery Pack Deterioration
P0A80Replace Hybrid Battery Pack
P0A94DC/DC Converter Performance
U0293Lost Communication with Hybrid Vehicle Control System
U0111Lost Communication with Battery Energy Control Module

Got a different code? Look it up — the index covers every standard OBD-II code.

Common questions

Can you drive with the hybrid system warning light on?: Usually yes, as far as a garage, provided the lamp is amber, nothing red is lit alongside it and the car is driving normally. The hybrid controller has logged a fault and will often keep the car running on the petrol engine while it does so. Stop and call for help if a red warning appears, if the car loses power, or if you smell anything hot or acrid.
Do hybrid cars need an MOT and an emissions test?: Yes to both. Hybrids follow the same MOT schedule as everything else, and because they have a petrol engine and an exhaust they take the full emissions test — the exemption people have heard about applies only to battery-electric and hydrogen fuel cell cars. Hybrids first used on or after 1 July 2003 are also failed if the engine malfunction indicator lamp is illuminated, exactly as a conventional petrol car would be.
What is the difference between the hybrid system light and the engine light?: They report to different bosses. The engine management lamp is the emissions-related malfunction indicator required by law and is set by the engine control unit. The hybrid system lamp is manufacturer-specific and covers the electric side: the motor-generators, inverter, converter and traction battery. A fault can light one, the other, or both, and only the engine lamp is an automatic MOT failure. If both are lit, read the codes from the hybrid modules as well as the engine, because a basic code reader only sees half the picture.
Can a flat 12-volt battery cause hybrid warning lights?: Very often, and it is the first thing worth eliminating. Hybrids and EVs still run all their control units, contactors and network communication from a conventional 12-volt battery, and when it weakens the modules brown out and start reporting each other as missing. The result is a dashboard full of unrelated warnings — hybrid system, ABS, stability control, parking brake — that all clear the moment a healthy battery goes in. A battery test costs very little and can save an expensive diagnostic.

This is general guidance, not a diagnosis. Manufacturers draw the same system differently and reuse symbols for more than one function, so check the handbook for your own car before acting on anything here.

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