Symptom

Engine will not shut off

The engine keeps running after the key is turned off. Almost exclusively a diesel fault, since cutting fuel is the only way to stop a compression-ignition engine. Have the vehicle recovered rather than driven.

Also described as: won't turn off, keeps running, runs on, dieseling, won't stop, engine won't switch off, موتور خاموش نمیشود, ماشین خاموش نمیشه, no puedo apagar motor, sigue en marcha sin llave, motor sigue encendido, sigue funcionando al quitar la llave, المحرك يستمر بالعمل بعد سحب المفتاح, لا أستطيع إطفاء المحرك, تظل شغالة بدون مفتاح

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Some causes mean you should stop driving

4 of the 9 codes that produce this symptom indicate a fault where continuing to drive risks damage or is unsafe. If the symptom is sudden or severe, treat it as one of those until a scan says otherwise.

What this usually means

Treat this as urgent rather than as an inconvenience, and have the vehicle recovered rather than driven. A diesel that will not stop can be running on something other than its fuel supply, and that condition destroys engines and starts fires.

A petrol engine and a diesel engine stop for completely different reasons, which is why this complaint is almost exclusively a diesel one. Cut the spark and a petrol engine stops immediately. A compression-ignition engine has no spark to cut, so the only way to stop it is to take away its fuel — and anything that keeps supplying combustible material keeps it running.

The dangerous version is a runaway, and it is worth being able to recognise. If the engine is drawing engine oil into the intake — past failed turbocharger seals, or through a crankcase ventilation system pushing oil into the inlet — it is burning its own lubricant, has no throttle authority over its own speed, and will accelerate until it seizes or comes apart. The tells are rising engine speed with the key off, heavy blue-white smoke, and a roar that does not respond to anything. The recognised emergency responses are to stall it against the transmission in a high gear with the brakes hard on, or to block the air intake completely; both are last resorts and both are safer than standing next to it.

The undramatic version is electrical and far more common. German references describe fuel pumps and injection supplies that keep running because a relay's contacts have welded closed or an ignition switch is not breaking the circuit — the engine idles on quite normally and simply does not stop. On a modern diesel a fuel shut-off or metering solenoid stuck open does the same thing.

Working through it

What you find	Likely cause	How to confirm it	What fixes it
Engine speed rises on its own with the key off, thick blue-white smoke, uncontrollable roar	Runaway — the engine is burning its own oil, drawn in past turbo seals or through the crankcase ventilation	Do not attempt to diagnose while it runs. Recognise it and stop it: stall it in a high gear against the brakes, or block the air intake completely. Stand clear.	Do not restart. Recover the vehicle. Repair the turbocharger seals or crankcase ventilation, and inspect the engine for damage before it is run again.
Idles normally with the key off and stops if the fuel supply is interrupted	The fuel supply is not being switched off — a welded relay contact or an ignition switch not breaking the circuit	Check whether the fuel pump or injection supply relay is still energised with the ignition off, and test the switch's output in each position.	Renew the relay or the ignition switch. A welded contact will not un-weld and the fault will return.
Modern diesel, runs on with no smoke and no rise in speed	Fuel shut-off or metering solenoid stuck open, so the rail is still being fed	Read the solenoid's commanded state against its actual behaviour with the ignition off, and check its supply is genuinely being removed.	Renew the solenoid, or repair the supply that is not being switched. Do not leave the vehicle in service with this fault.
Petrol engine that runs on roughly for a few seconds and dies	Run-on from hot carbon deposits igniting the mixture, or an idle setting leaving too much air and fuel at shutdown	Distinguish from a genuine no-shutdown: run-on stops by itself. Check idle speed and the throttle plate for carbon.	Decarbonise and correct the idle setting. On a modern engine also check the throttle adaptation.
Started after work on the immobiliser, ignition or wiring	A circuit bridged or a relay wired to permanent live during the work	Retrace exactly what was changed. A car that stopped correctly last week and does not now is a wiring change, not a component failure.	Restore the correct wiring. Do not add a switch to work around it.

Engine speed rises on its own with the key off, thick blue-white smoke, uncontrollable roar

Likely cause

Runaway — the engine is burning its own oil, drawn in past turbo seals or through the crankcase ventilation

How to confirm it

Do not attempt to diagnose while it runs. Recognise it and stop it: stall it in a high gear against the brakes, or block the air intake completely. Stand clear.

What fixes it

Do not restart. Recover the vehicle. Repair the turbocharger seals or crankcase ventilation, and inspect the engine for damage before it is run again.
Idles normally with the key off and stops if the fuel supply is interrupted

Likely cause

The fuel supply is not being switched off — a welded relay contact or an ignition switch not breaking the circuit

How to confirm it

Check whether the fuel pump or injection supply relay is still energised with the ignition off, and test the switch's output in each position.

What fixes it

Renew the relay or the ignition switch. A welded contact will not un-weld and the fault will return.
Modern diesel, runs on with no smoke and no rise in speed

Likely cause

Fuel shut-off or metering solenoid stuck open, so the rail is still being fed

How to confirm it

Read the solenoid's commanded state against its actual behaviour with the ignition off, and check its supply is genuinely being removed.

What fixes it

Renew the solenoid, or repair the supply that is not being switched. Do not leave the vehicle in service with this fault.
Petrol engine that runs on roughly for a few seconds and dies

Likely cause

Run-on from hot carbon deposits igniting the mixture, or an idle setting leaving too much air and fuel at shutdown

How to confirm it

Distinguish from a genuine no-shutdown: run-on stops by itself. Check idle speed and the throttle plate for carbon.

What fixes it

Decarbonise and correct the idle setting. On a modern engine also check the throttle adaptation.
Started after work on the immobiliser, ignition or wiring

Likely cause

A circuit bridged or a relay wired to permanent live during the work

How to confirm it

Retrace exactly what was changed. A car that stopped correctly last week and does not now is a wiring change, not a component failure.

What fixes it

Restore the correct wiring. Do not add a switch to work around it.

Codes that produce this symptom (9)

Listed with the codes that most typically present this way first — the likeliest place to start.

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.

Others with this symptom

Be the first to write this up

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What makes one worth reading:

The car — make, model, year and engine. The same fault behaves differently on each.
What you measured, not only what you replaced.
What actually fixed it — or that nothing did, which is worth knowing too.