Code dictionary Generic OBD-II
P0304Cylinder 4 Misfire Detected
This is a definition, not a repair instruction. It does not identify a failed part or establish that a vehicle is safe to drive.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Separately researched
Vehicle-specific diagnosis
These guides address the exact vehicles and conditions in their sources. Select the guide that matches your vehicle.
Honda
Honda CR-V P0300 and P0172: separate update, plug and camshaft branches
2017–2018 CR-V: repair history, spark-plug findings and a separate noise inspection determine which Honda procedure applies.
Honda
Honda Accord V6 P0301–P0304: software, fouled plugs or piston rings?
Plug fouling, software and cylinder codes select the documented repair branch.
Ford
2018 F-150 P0300 and P0171: when injectors are actually implicated
Follow the code and build-date branches before approving injector replacement.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT