P0300 on a 2013 GMC Sierra 1500

P0300 is a generic OBD2 powertrain code for random or multiple cylinder misfire. Unlike P0301 through P0308, it does not point to one specific cylinder, so the cause can be ignition, fuel, air, sensor, or mechanical.

Not your vehicle? See general P0300 info.

Most common causes on the 2013 GMC Sierra 1500

Ranked from 167 NHTSA owner complaints filed for this vehicle.

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1
Active Fuel Management (AFM) Lifter Failure
High severity
Listen for a loud ticking, clattering, or popping noise from the engine, often accompanied by a misfire and loss of power. This is a well-documented issue with the 5.3L V8 AFM system where lifters collapse or fail.
Reported in 4 NHTSA complaints
2
Faulty Piston Rings / Excessive Oil Consumption
High severity
Check for excessive oil consumption, fouled spark plugs, and rattling noises. Worn or faulty piston rings can lead to low compression and misfires.
Reported in 2 NHTSA complaints
3
Camshaft Damage
High severity
Inspect the camshaft lobes for scoring or wear, which often occurs secondary to AFM lifter failure. This will cause severe misfires and loud engine noises.
Reported in 2 NHTSA complaints
4
Broken Lifter Springs
High severity
Inspect the fuel management lifter springs for breakage. This causes the engine to misfire heavily and struggle to idle.
Reported in 1 NHTSA complaint
5
Worn Spark Plugs or Ignition Coils
Low severity
Check for worn spark plug electrodes or degraded ignition coils. These are standard maintenance items that commonly cause random misfires.
Common cause
6
Vacuum Leak
Medium severity
Inspect intake manifold gaskets and vacuum hoses for leaks. Unmetered air entering the engine causes a lean condition and random misfires.
Common cause
7
Low Fuel Pressure / Clogged Fuel Injectors
Medium severity
Test fuel pressure and inspect injectors. Inadequate fuel delivery can cause multiple cylinders to misfire.
Common cause

These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0300 on your car still needs shop confirmation before any repair.

Common symptoms

Flashing or steady check engine light
Rough idle
Shaking under acceleration
Loss of power
Fuel smell from exhaust

What to check before replacing parts

Scan for cylinder-specific misfire codes

Look for: A companion P0301–P0308 pins the misfire to one cylinder — start there. P0300 with no cylinder code points at something hitting several at once: fuel pressure, a large vacuum leak, or timing.

Inspect the spark plugs and coils

Look for: Pull the plugs: black/sooty = rich, oily = oil intrusion, white/blistered = lean or overheating, cracked porcelain or an out-of-spec gap = replace. Then swap a coil to another cylinder — if a cylinder-specific code follows the coil, the coil is bad.

Check fuel trims for a vacuum leak

Look for: High positive short- and long-term trims (worst at idle, improving as RPM rises) mean unmetered air is getting in. Smoke-test the intake and listen for hissing.

Verify fuel pressure

Look for: Compare running/cranking pressure to the vehicle spec. Low or dropping pressure starves multiple cylinders and reads as a random misfire — suspect the pump, filter, or regulator.

Compression / leak-down test if ignition and fuel check out

Look for: A cylinder 15%+ below the others, or leak-down hissing from the intake (intake valve), exhaust (exhaust valve), or oil filler (rings), means the misfire is mechanical — not a swap-in part.

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Matching symptoms

Car Runs Rough Flashing Check Engine Light