Symptom
Check engine light flashing
A flashing lamp means an active misfire severe enough to damage the catalytic converter. This is the one warning that genuinely means stop as soon as it is safe, rather than book it in.
Also described as: flashing engine light, blinking check engine light, flashing mil, blinking engine light, flashing warning light, چراغ چک چشمک میزند, چراغ چک چشمک میزنه, چراغ چک پلک میزند, check engine parpadeando, luz motor parpadea, testigo motor intermitente, luz check parpadeando, luz motor parpadeando, لمبة المحرك تنور وتطفي, علامة المحرك ترمش, لمبة الفحص ترفرف
Some causes mean you should stop driving
90 of the 90 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
This is the one dashboard warning that means stop as soon as it is safe, rather than book it in. Reduce load immediately, avoid high revs, and pull over where you can.
A flashing lamp is not a worse version of a steady one; it reports a different thing. It means the management is detecting misfire at a rate it considers damaging right now — and the damage is not to the engine, it is to the catalytic converter.
The mechanism is worth knowing because it explains the urgency. A misfiring cylinder does not burn its charge, so raw fuel goes out of the exhaust valve into a catalyst already running at several hundred degrees. There it ignites on the catalyst rather than in the cylinder. German references put the resulting monolith temperature above 1,000 °C, which is beyond what the ceramic substrate can survive: it melts, partially fuses, and the converter becomes a restriction. So a misfire that would have cost a coil turns into a catalytic converter, and it does so in minutes of driving rather than over weeks.
The load relationship is the useful diagnostic detail. A misfire that flashes under acceleration and settles to a steady lamp at idle is telling you it appears when cylinder pressure and charge demand are highest — which fits an ignition component breaking down under load, an injector that cannot keep up, or a compression loss that only matters when the cylinder is asked to work. That is exactly why continuing gently to a garage is more damaging than stopping: every acceleration is another dose of raw fuel into a converter that is already too hot.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Flashing while driving, engine rough or shaking | Active misfire at a rate the management considers damaging to the catalyst | None required roadside. Reduce load, avoid high revs, and stop where it is safe. Diagnosis begins once it is stationary. | Do not drive on to see whether it settles. Recover the vehicle if the distance is more than very short. |
| Flashes under acceleration, steady at idle | A misfire that appears with load — ignition breaking down under cylinder pressure, an injector that cannot keep up, or lost compression | Read misfire counters per cylinder, which name the cylinder without any dismantling. Then swap the coil or injector to a different cylinder and see whether the count follows it. | Renew whichever component the count follows. If the misfire stays with the cylinder after both are swapped, it is compression and needs a leak-down test. |
| Flashing with a strong smell of unburnt fuel | Raw fuel reaching the exhaust — the same misfire, confirmed by nose | This corroborates rather than adds. It raises urgency because it means a substantial quantity is getting through, not a trace. | Stop. Do not restart to reposition the car any more than necessary. |
| Flashed for a while, now steady, and the car feels flat | The misfire has stopped being severe, and the catalyst may already be restricted from the episode | Test exhaust backpressure: under roughly 1.5 psi (10 kPa) at idle and under about 3 psi (20 kPa) at 2,000 rpm on most engines. A high pre-catalyst reading with a low post-catalyst one localises the blockage to the converter. | Repair the misfire first, then assess the catalyst. Fitting a converter before the misfire is cured destroys the new one too. |
| Started flashing immediately after ignition or injector work | A coil connector, plug lead or injector plug not seated | Retrace what was disturbed before reaching for a scan tool. The misfire counter will name the cylinder and it will be one that was touched. | Reseat the connection. This is the cheapest entry on the page and the one worth checking first after any work. |
| Flashing on a diesel | Less common, because a diesel has no spark to lose — points at injector or compression faults rather than ignition | Read misfire counters and injector correction values, and measure injector leak-off across the set. | Repair the injector or compression fault found. The catalyst risk is different on a diesel but the aftertreatment is still not designed for raw fuel. |
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Flashing while driving, engine rough or shaking
- Likely cause
- Active misfire at a rate the management considers damaging to the catalyst
- How to confirm it
- None required roadside. Reduce load, avoid high revs, and stop where it is safe. Diagnosis begins once it is stationary.
- What fixes it
- Do not drive on to see whether it settles. Recover the vehicle if the distance is more than very short.
-
Flashes under acceleration, steady at idle
- Likely cause
- A misfire that appears with load — ignition breaking down under cylinder pressure, an injector that cannot keep up, or lost compression
- How to confirm it
- Read misfire counters per cylinder, which name the cylinder without any dismantling. Then swap the coil or injector to a different cylinder and see whether the count follows it.
- What fixes it
- Renew whichever component the count follows. If the misfire stays with the cylinder after both are swapped, it is compression and needs a leak-down test.
-
Flashing with a strong smell of unburnt fuel
- Likely cause
- Raw fuel reaching the exhaust — the same misfire, confirmed by nose
- How to confirm it
- This corroborates rather than adds. It raises urgency because it means a substantial quantity is getting through, not a trace.
- What fixes it
- Stop. Do not restart to reposition the car any more than necessary.
-
Flashed for a while, now steady, and the car feels flat
- Likely cause
- The misfire has stopped being severe, and the catalyst may already be restricted from the episode
- How to confirm it
- Test exhaust backpressure: under roughly 1.5 psi (10 kPa) at idle and under about 3 psi (20 kPa) at 2,000 rpm on most engines. A high pre-catalyst reading with a low post-catalyst one localises the blockage to the converter.
- What fixes it
- Repair the misfire first, then assess the catalyst. Fitting a converter before the misfire is cured destroys the new one too.
-
Started flashing immediately after ignition or injector work
- Likely cause
- A coil connector, plug lead or injector plug not seated
- How to confirm it
- Retrace what was disturbed before reaching for a scan tool. The misfire counter will name the cylinder and it will be one that was touched.
- What fixes it
- Reseat the connection. This is the cheapest entry on the page and the one worth checking first after any work.
-
Flashing on a diesel
- Likely cause
- Less common, because a diesel has no spark to lose — points at injector or compression faults rather than ignition
- How to confirm it
- Read misfire counters and injector correction values, and measure injector leak-off across the set.
- What fixes it
- Repair the injector or compression fault found. The catalyst risk is different on a diesel but the aftertreatment is still not designed for raw fuel.
Codes that produce this symptom (90)
Listed with the codes that most typically present this way first — the likeliest place to start.
- P0300 Random/Multiple Cylinder Misfire Detected Typical of this code Stop driving High
- P0301 Cylinder 1 Misfire Detected Typical of this code Stop driving High
- P0302 Cylinder 2 Misfire Detected Typical of this code Stop driving High
- P0303 Cylinder 3 Misfire Detected Typical of this code Stop driving High
- P0304 Cylinder 4 Misfire Detected Typical of this code Stop driving High
- P0305 Cylinder 5 Misfire Detected Typical of this code Stop driving High
- P0306 Cylinder 6 Misfire Detected Typical of this code Stop driving High
- P0307 Cylinder 7 Misfire Detected Typical of this code Stop driving High
- P0308 Cylinder 8 Misfire Detected Typical of this code Stop driving High
- P0309 Cylinder 9 Misfire Detected Typical of this code Stop driving High
- P0310 Cylinder 10 Misfire Detected Typical of this code Stop driving High
- P0311 Cylinder 11 Misfire Detected Typical of this code Stop driving High
- P0312 Cylinder 12 Misfire Detected Typical of this code Stop driving High
- P0363 Misfire Detected — Fuelling Disabled Typical of this code Stop driving Critical
- P2146 Fuel Injector Group A Supply Voltage Circuit/Open Typical of this code Stop driving High
- P2147 Fuel Injector Group A Supply Voltage Circuit Low Typical of this code Stop driving High
- P2148 Fuel Injector Group A Supply Voltage Circuit High Typical of this code Stop driving High
- P2149 Fuel Injector Group B Supply Voltage Circuit/Open Typical of this code Stop driving High
- P2150 Fuel Injector Group B Supply Voltage Circuit Low Typical of this code Stop driving High
- P2151 Fuel Injector Group B Supply Voltage Circuit High Typical of this code Stop driving High
- P2152 Fuel Injector Group C Supply Voltage Circuit/Open Typical of this code Stop driving High
- P2153 Fuel Injector Group C Supply Voltage Circuit Low Typical of this code Stop driving High
- P2154 Fuel Injector Group C Supply Voltage Circuit High Typical of this code Stop driving High
- P2155 Fuel Injector Group D Supply Voltage Circuit/Open Typical of this code Stop driving High
- P2156 Fuel Injector Group D Supply Voltage Circuit Low Typical of this code Stop driving High
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.
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