P0301 on a GMC: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

If the check engine light is flashing, stop driving — a severe misfire can damage the catalytic converter. A steady light is usually safe for a short drive to a shop.

What P0301 means on a GMC

On a GMC, P0301 means the engine computer has detected that cylinder 1 is not firing properly and is failing to contribute its share of power. Because it is a single-cylinder code, the fault is usually something specific to cylinder 1, like its spark plug, ignition coil, or fuel injector.

Is P0301 common on GMCs?

P0301 is common on GMC V8s like the 5.3L in the Sierra and Yukon, where worn spark plugs and coil-on-plug ignition coils are the usual causes at higher mileage. The four-cylinder engines in the Terrain and Acadia can also misfire from coil or plug wear. On V8s with Active Fuel Management, a collapsed lifter is a known cause of a single-cylinder misfire.

Commonly reported on: Sierra, Yukon, Terrain, Acadia.

Symptoms

Check engine light on (flashing if severe)
Rough idle or shaking at a stop
Loss of power or hesitation under acceleration
Poor fuel economy

Common causes

most common: Worn or fouled spark plug in cylinder 1
common: Failing ignition coil for cylinder 1
common: Clogged or leaking fuel injector in cylinder 1
less common: Collapsed lifter from Active Fuel Management on V8 models
less common: Low compression in cylinder 1 from engine wear

How to fix it

Fix	DIY?	Typical cost
Replace the spark plug in cylinder 1	Yes	$30–120
Replace the ignition coil for cylinder 1	Yes	$80–300
Clean or replace the fuel injector in cylinder 1	Mechanic	$150–600
Have a shop check the lifters and run a compression test on V8 models	Mechanic	$200–500