P0300 on a 2021 Chevrolet Silverado 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 2021 Chevrolet Silverado 1500
Ranked from 772 NHTSA owner complaints filed for this vehicle.
- 1
AFM lifter/camshaft valvetrain collapse (6.2L L87 V8)
High severityMultiple owners report backfiring, shuddering, or cylinder-specific misfire traced by technicians to collapsed lifters, worn cam lobes, or a bent pushrod on the Active Fuel Management V8 -- a well-documented failure mode on this engine.
Reported in 5 NHTSA complaints - 2
Failing ignition coil or coil-on-plug pack
Medium severityAn owner traced a persistent cylinder-specific misfire by swapping coil packs between cylinders and the misfire followed the coil, pointing to a bad coil rather than the plug.
Reported in 1 NHTSA complaintParts:ignition coil - 3
Low cylinder compression from worn valve seals/rings
High severityA borescope inspection found excess oil pooled on a piston top and carbon debris scoring the cylinder wall, tracing a cylinder-3 misfire and low compression to leaking valve seals.
Reported in 1 NHTSA complaintParts:valve stem seals - 4
Worn or fouled spark plugs
Low severityOriginal-equipment plugs wear or foul with carbon over tens of thousands of miles, weakening spark and producing random misfires across multiple cylinders.
Common causeParts:spark plugs - 5
Vacuum or intake air leak
Low severityCracked hoses or a loose intake connection let unmetered air in, leaning out individual cylinders enough to misfire, most noticeable at idle.
Common cause - 6
Clogged or leaking fuel injector
Medium severityA partially clogged or dribbling injector starves or floods a single cylinder, producing a repeatable misfire on that cylinder.
Common causeParts:fuel injectors - 7
EGR valve stuck open or faulty
Low severityExcess exhaust gas recirculated at the wrong time dilutes the intake charge and can trigger misfire, especially at idle or light load.
Common causeParts:EGR valve
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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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