Possible causes

– 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

Tech notes

The P0303 code means that the cylinder 3 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 3. If the problem persist more tests needs to be done to diagnose problem, see “Possible Causes”

When is the code detected?

Engine Cylinder 3 is Misfiring.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Lack/loss of power
– Hard start
– Engine hesitation

P0303 Description

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.

P0303 Information for specific makes

P0303 BMW
P0303 CHRYSLER
P0303 JEEP
P0303 DODGE
P0303 NISSAN
P0303 INFINITI
P0303 ISUZU
P0303 KIA
P0303 LEXUS
P0303 SCION
P0303 TOYOTA
P0303 SATURN
P0303 MAZDA
P0303 MITSUBISHI
P0303 SUBARU
P0303 VOLKSWAGEN
P0303 AUDI
P0303 HYUNDAI
P0303 CHEVROLET
P0303 GMC
P0303 PONTIAC
P0303 FORD
P0303 BUICK
P0303 CADILLAC
P0303 MERCURY
P0303 VOLVO
P0303 HUMMER
P0303 JAGUAR
P0303 ACURA
P0303 HONDA