P0300 on a 2021 Chevrolet Tahoe

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 Tahoe

Ranked from 423 NHTSA owner complaints filed for this vehicle.

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1
AFM/DFM valve lifter collapse (Dynamic Fuel Management system failure)
High severity
This is the dominant, well-documented failure mode for the GM 5.3L/6.2L L84/L87 engine family: a Dynamic Fuel Management lifter collapses and drops a valve, producing a sudden random/multi-cylinder misfire, violent shaking, and a knocking noise. Multiple complaints describe exactly this — one explicitly logs P0300 with correlating P0011/P0016 cam-crank misalignment codes, another documents 'all 8 lifters on one bank' failed, and others were confirmed at teardown to have a dropped lifter or camshaft damage.
Reported in 7 NHTSA complaints
Parts:valve lifters (AFM/DFM)camshaft
2
Connecting rod / rod bearing failure (GM 5.3L/6.2L 'loss of propulsion' recall pattern)
High severity
Several owners had the engine seize or 'blow' with a loud clunk/bang and a knock immediately preceding total power loss, and dealers specifically diagnosed a bent connecting rod or failed crankshaft — the same defect covered by NHTSA Campaign 25V274 on this engine family, which one owner's VIN was excluded from despite an identical failure.
Reported in 6 NHTSA complaints
3
Low compression from worn piston rings / chronic oil consumption
Medium severity
Multiple complaints on this same engine describe heavy oil consumption (3+ quarts between changes) with blue exhaust smoke and, in one case, metal shavings found in the oil at teardown — internal wear that lowers compression and can present as a misfire.
Reported in 4 NHTSA complaints
4
EGR system fault
Low severity
A stuck-open EGR valve or a leaking EGR passage dumps excess exhaust gas into the intake at the wrong time, causing a lean misfire; one complaint on this same vehicle logged concurrent EGR pressure sensor and NOx-related fault codes.
Reported in 1 NHTSA complaint
Parts:EGR valve
5
Worn or fouled spark plugs
Low severity
Standard high-mileage misfire cause; worn electrodes or carbon-fouled plugs cause an intermittent spark that shows up as a random/multi-cylinder misfire code.
Common cause
Parts:spark plugs
6
Failing ignition coil(s)
Medium severity
A weak or intermittently failing coil starves one cylinder of spark; swapping coils between cylinders and watching whether the misfire follows the coil confirms this.
Common cause
Parts:ignition coil
7
Vacuum or intake leak
Low severity
Unmetered air entering through a cracked hose or intake gasket leans out the affected cylinder(s) enough to cause a misfire, particularly at idle.
Common cause

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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