P0303 on a Chevy: 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 Chevy

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

Is P0303 common on Chevys?

P0303 appears on Chevys with higher mileage, especially the Silverado, Equinox, and Malibu. Worn spark plugs and failing coil-on-plug ignition coils are the usual causes. On Chevy V8 trucks with cylinder deactivation, a failed lifter can also cause a single-cylinder misfire, though this is less common.

Commonly reported on: Silverado, Equinox, Malibu, Tahoe.

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: Failed cylinder deactivation lifter on V8 models
less common: Low compression in cylinder 3

How to fix it

Fix	DIY?	Typical cost
Swap the cylinder 3 coil and plug with another cylinder to confirm which part is bad	Yes	$0–20
Replace the cylinder 3 spark plug	Yes	$10–50
Replace the cylinder 3 ignition coil	Yes	$50–200
Have cylinder 3 compression-tested	Mechanic	$100–200