P0304 Code: Meaning, Causes, and Symptoms | OBD2 Codes

P0304 – Cylinder 4 Misfire Detected


P0304: DIY Repairing Video Tutorial


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P0304 Possible Causes

Faulty spark plug 4

Clogged or faulty fuel injector 4

Faulty ignition coil 4

Fuel injector 4 harness is open or shorted

Fuel injector 4 circuit poor electrical connection

Ignition coil 4 harness is open or shorted

Ignition coil 4 circuit poor electrical connection

Insufficient cylinder 4 compression

Incorrect fuel pressure

Intake air leak

P0304 Possible Symptoms

Engine Light ON (or Service Engine Soon Warning Light)

Lack/loss of power

Hard start

Engine hesitation


When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.