P0303 on a Honda: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

You can usually drive short distances with a steady light, but stop right away if the light flashes — a severe misfire can damage the catalytic converter.

What P0303 means on a Honda

On a Honda, P0303 means the computer has flagged cylinder 3 for misfiring. The problem is local to cylinder 3 — its spark plug, ignition coil, or fuel injector — rather than a system-wide issue.

Is P0303 common on Hondas?

P0303 appears on Hondas with higher mileage, often on the Civic, Accord, and CR-V. Honda coil-on-plug ignition units and spark plugs wear with age and are common causes of single-cylinder misfires. On some Honda engines, valves that are out of adjustment can also cause a cylinder 3 misfire.

Commonly reported on: Civic, Accord, CR-V, Pilot.

Symptoms

Check engine light on (flashing if severe)
Rough, shaky idle
Loss of power or hesitation
Poor fuel economy

Common causes

most common: Worn or fouled spark plug on cylinder 3
common: Failing ignition coil on cylinder 3
common: Clogged or leaking fuel injector on cylinder 3
less common: Valves out of adjustment on cylinder 3
less common: Low compression in cylinder 3

How to fix it

Fix	DIY?	Typical cost
Replace the cylinder 3 spark plug	Yes	$10–50
Replace the cylinder 3 ignition coil	Yes	$60–200
Have the valves adjusted	Mechanic	$150–400
Have cylinder 3 compression-tested	Mechanic	$100–200