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
- Coil power supply: fuse or relay
- Ignition coil
- Coil wiring
- ECU (rarely)
What you can do yourself
- Check the coil power fuse (IG COIL, IGN).
- Swap the coil with the neighbouring one: if the code moves, replace the coil.
- Check the coil connector.
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: check the connector
Often the cause is simple — there is no contact in the connector (plug). Look at the connector from the back: remove the rubber seal and you will see whether a wire is corroded or has come off completely. Corrosion shows up as green deposits. Ideally, gently pull each wire towards you one at a time: a sound wire stays in place, while a corroded one simply comes off — it needs to be repaired.
Unplug and inspect connectors with the ignition off.
OA case from Oleg’s practice
- Nissan X-Trail 2002 Check Engine on: P0328 (knock sensor) and P0350 (coil circuit). The codes showed where to look — coils, plugs, wiring and the sensor — not what to replace right away. How it went ↗
On Oleg’s website:Ignition module repair ↗
The explanation comes from the error code reference in the AvtoElektrik PRO app.