P0300 on a 2016 GMC Yukon Denali Xl 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 2016 GMC Yukon Denali Xl 1500

Ranked from 497 NHTSA owner complaints filed for this vehicle.

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1
AFM/DFM lifter, camshaft, or pushrod failure (collapsed lifter)
High severity
An overwhelming, repeated pattern on this exact 6.2L engine: collapsed/failed cylinder-deactivation lifters and bent pushrods (bad cam lobes) leave a valve unable to open on one or more cylinders, causing severe skipping/rough-running and frequently full engine replacement.
Reported in 18 NHTSA complaints
Parts:valve lifters camshaft pushrods
2
Coolant intrusion into a cylinder from an internal engine leak
High severity
One owner's engine was found to have a microscopic pinhole letting coolant sit under an injector after a tune-up -- coolant fouling a cylinder or plug produces a persistent misfire.
Reported in 1 NHTSA complaint
3
Worn or fouled spark plugs
Medium severity
Degraded or oil/carbon-fouled plugs are a baseline cause of random misfire on any engine and should be checked/gapped before deeper diagnosis.
Common cause
Parts:spark plugs
4
Failing ignition coil(s)
Medium severity
A coil breaking down under load or heat drops spark energy to a single cylinder, producing a repeatable single-cylinder misfire.
Common cause
Parts:ignition coil
5
Clogged or leaking fuel injector(s)
Medium severity
A restricted or dribbling injector under- or over-fuels one cylinder, producing a misfire on that cylinder specifically.
Common cause
Parts:fuel injector
6
Vacuum or intake air leak
Medium severity
Unmetered air entering the intake leans one or more cylinders enough to cause an intermittent misfire, especially at idle.
Common cause
7
EGR system fault
Low severity
Excess or mistimed EGR flow over-dilutes the intake charge and can trigger a misfire at idle and light load.
Common cause
Parts: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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Matching symptoms

Car Runs Rough Flashing Check Engine Light