P0300 on a 2020 Ford F 150 Super Crew Diesel

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 2020 Ford F 150 Super Crew Diesel

Ranked from 506 NHTSA owner complaints filed for this vehicle.

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1
Camshaft phaser (VCT) failure
High severity
A large cluster of owners had cam phasers diagnosed and replaced for a rattling/knocking cold-start noise and rough idle, including one case where failed phaser sensors caused the engine to stall and accelerate poorly; incorrect valve timing from worn phasers is a documented misfire source on this V8.
Reported in 6 NHTSA complaints
Parts:camshaft phaser timing chain timing chain guide
2
Low compression from the engine's known oil-consumption defect
High severity
Multiple owners document excessive oil consumption (up to 2 quarts per 1,300 miles) serious enough to require engine replacement, including one case where running low on oil led to a cracked crankshaft and metal shavings in the short block; worn rings/bearings from oil starvation cause rough running and misfire.
Reported in 5 NHTSA complaints
3
Worn or fouled spark plugs
Low severity
Standard high-mileage wear item and the most common generic cause of a random misfire code.
Common cause
Parts:spark plugs
4
Vacuum or intake air leak
Medium severity
Unmetered air entering after the MAF leans out individual cylinders enough to cause an intermittent misfire, especially at idle.
Common cause
5
Clogged or leaking fuel injector
Medium severity
An injector delivering too little or unevenly starves a cylinder of fuel and is a common misfire source on direct-injected V8s.
Common cause
Parts:fuel injector
6
EGR valve fault (stuck open)
Low severity
An EGR valve stuck open at idle/low load dilutes the intake charge enough to cause a rough idle or misfire.
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