P0303 Chevy Silverado: Cylinder 3 Misfire Diagnosis and Fix

P0303 on a Chevy Silverado means cylinder 3 is misfiring. Cylinder 3 is the second cylinder from the front on the driver’s side. The diagnosis is the same as any single-cylinder misfire — start with the coil and work inward.

Watch a cylinder-specific misfire traced to a failed ignition coil — the same plug, spark and coil checks apply to P0303.

Cylinder 3 Location

Driver’s side cylinders front-to-rear = 1, 3, 5, 7. Cylinder 3 is the second cylinder from the front on the driver’s side. It sits directly above the driver-side catalytic converter on most Silverado configurations, which means a P0303 misfire left unaddressed can cause converter damage faster than misfires on other cylinders.

Common Causes

Failed ignition coil on cylinder 3, worn spark plug, defective fuel injector. Cylinder 3 is NOT an AFM deactivation cylinder on the 5.3L — AFM affects cylinders 1, 4, 6, 7. Standard diagnosis applies without the AFM lifter complication.

Diagnosis

Swap the cylinder 3 coil to cylinder 1 or 5. If the misfire code moves, replace the coil. Inspect and replace the spark plug if worn. If coil and plug are good, test injector by swapping the injector harness connector to an adjacent cylinder. Compression test on cylinder 3 if all else checks out. Related codes: P0300, P0301, P0305.

Repair Cost Estimate

Ignition coil replacement (cylinder 3): $30–60 parts, 20 minutes labor. Spark plug: $6–15 parts, 20 minutes. Fuel injector: $35–80 parts, $100–200 shop labor. Full tune-up (all 8 plugs and coils): $120–200 in parts — if one coil fails, the others are likely near end of life. Consider doing all 8 when replacing one on higher-mileage trucks.