Fault codes › Powertrain › Generic (SAE standard) › Ignition system or misfire › Misfire — random or multiple cylinders

P0303 Cylinder 3 misfire

Urgent Risk of damage or of being stranded. Stop, or get it seen, now.

What does P0303 mean?

P0303 is a generic powertrain code, defined by the SAE standard, so it means the same thing on every make and model: cylinder 3 misfire. It belongs to the ignition system or misfire group of codes.

A control module stores the code when something it watches stays outside what it expects for long enough. On its own the code says which system complained, not which part has failed — the causes below, most likely first, are where to start.

Is it safe to drive with P0303?

Urgent. As P0301 — get it fixed promptly.

Common causes of P0303

Spark plug or coil on cylinder 3.
Injector fault.
Low compression.

Symptoms

Vibration.
Power loss.

What to check first

Coil/plug swap test.
Compression on cylinder 3.

Can I just clear P0303?

You can, and the light goes out — but a fault that is still there sets the code again, often within a drive or two. Clearing also erases the freeze frame (what the engine was doing when the code was stored) and resets the emissions readiness monitors, so an MOT, smog or inspection test will wait until they have run again. Fix the cause first, then clear it, then watch whether it returns.

Read and clear P0303 from your iPhone with OBDTrip

Plug a Bluetooth OBD-II adapter into the car and OBDTrip reads every stored, pending and permanent code, explains each one in plain English like this, shows what the engine was doing when it was set, and clears the check engine light once the fault is fixed. It keeps a history of when each code comes back, and records every drive on its own from then on.

Needs a Bluetooth Low Energy adapter such as the Vgate iCar Pro — which adapters work with iPhone. Reading and clearing codes is part of an OBDTrip subscription.

Related codes

General guidance from OBDTrip's fault-code catalogue, not a diagnosis of your car. When a code points to brakes, steering, overheating or a flashing check engine light, have the car looked at before driving on.