P0303 - Cylinder 3 Misfire Detected
Faulty spark plug 3
Clogged or faulty fuel injector 3
Faulty ignition coil 3
Fuel injector 3 harness is open or shorted
Fuel injector 3 circuit poor electrical connection
Ignition coil 3 harness is open or shorted
Ignition coil 3 circuit poor electrical connection
Insufficient cylinder 3 compression
Incorrect fuel pressure
Intake air leak
The P0303 code means that the cylinder 3 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder 3. If the problem persists more tests needs to be done to diagnose problem, see "Possible Causes"
When is the code detected?
Engine Cylinder 3 is Misfiring.
Engine Light ON (or Service Engine Soon Warning Light)
Lack/loss of power
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.