P0303 - Cylinder 3 Misfire Detected
Last updated:
System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0303 indicates that the Engine Control Unit (ECU) has detected a misfire event on cylinder number 3. The ECU monitors the crankshaft speed variations using the Crankshaft Position (CKP) sensor. If the crankshaft velocity drops during the power stroke of cylinder 3, a misfire is recorded. To prevent catalytic converter damage, the ECU may deactivate the fuel injector for the affected cylinder and activate limp mode. This diagnostic monitor is critical for emissions and catalyst longevity.
Possible Causes
Faulty spark plug or ignition coil (Cylinder 3)
Wiring issues or loose connector at the ignition coil
Defective fuel injector (clogged or electrical fault)
Internal engine mechanical failure (low compression, leaking valves, or worn camshaft)
Intake manifold gasket leak or vacuum leak near cylinder 3
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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