A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
Possible causes
- The spark plug of this cylinder
- Ignition coil or boot
- The injector of this cylinder
- Low compression (valves, rings)
What you can do yourself
- Swap this cylinder’s coil with the neighbouring one and clear the code. If the misfire “moves” to the other cylinder, the coil is to blame.
- Unscrew the spark plug: soot, oil or a cracked insulator — replace it.
- If Check Engine is flashing, don’t load the engine: unburned petrol damages the catalytic converter.
Stop and don’t drive on if:
- The Check Engine light is flashing
- The temperature gauge is in the red or the overheating light is on
- The red oil pressure light is on
- Smoke from under the bonnet, a burning or petrol smell
- Strong jerking, knocking from the engine, or the car barely moves
OOleg’s tip: don’t pressure-wash the engine
Never wash the engine with a Kärcher (a pressure washer), steam or anything like that — there’s a special foam cleaner for that. Once the rubber seals in the connectors have dried out, moisture gets inside and the sensor connectors and the computer (ECU) connector rot.
OCases from Oleg’s practice
- Volkswagen Passat 2002 Unstable idle, misfires, about fifteen codes stored. After cleaning and adapting the throttle body the idle became steadier; next we recommended the spark plugs, HT leads, O2 sensors, EVAP, MAF sensor and a search for air leaks. How it went ↗
- Haval M6 2023 Runs unevenly and stalls while driving: P0304, P0303, P0300, P0363. The spark plugs show burn marks and two have cracked ceramic; the coils and boots are intact. We recommended replacing the plug set with catalog-specified ones and rechecking. How it went ↗
On Oleg’s website:Engine compression test ↗
The explanation comes from the error code reference in the AvtoElektrik PRO app.