P0300 on a 2021 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 2021 Ford F 150 Super Crew Diesel
Ranked from 941 NHTSA owner complaints filed for this vehicle.
- 1
Low-pressure fuel pump failure (Ford recall 25V455/25S75) causing fuel starvation misfire/stall
High severityA large cluster of complaints on this exact truck document the recalled in-tank low-pressure fuel pump losing pressure, producing sputtering, hesitation, and outright stalling consistent with a fuel-starvation misfire.
Reported in 9 NHTSA complaintsParts:fuel pump - 2
Worn or cracked spark plugs
Medium severitySeveral misfire repairs on this vehicle started with spark plug replacement, including plugs found physically cracked.
Reported in 4 NHTSA complaintsParts:spark plugs - 3
Ignition coil failure
Medium severityCoil replacement was part of the misfire repair attempts on this vehicle, though not always resolving the code alone.
Reported in 2 NHTSA complaintsParts:ignition coil - 4
Failing or leaking fuel injector
High severityOne owner had a high-pressure injector confirmed cracked and spraying fuel, and another replaced all injectors while chasing a persistent misfire.
Reported in 2 NHTSA complaintsParts:fuel injector - 5
Valve/valvetrain failure causing low cylinder compression
High severityOne case found piston-top damage from a failed valve on a specific cylinder, confirmed by the dealer, producing a severe single-cylinder misfire.
Reported in 1 NHTSA complaint - 6
Timing chain or variable valve timing (VVT) fault
Medium severityA rattling sound with a check-engine light and a timing failure flagged by the Ford app points to a timing-related misfire cause.
Reported in 1 NHTSA complaintParts:timing chain - 7
Vacuum or intake air leak
Medium severityUnmetered air causes lean misfire, especially at idle; check intake boots and manifold gaskets with smoke.
Common cause - 8
Carbon-fouled intake valves (direct-injection carbon buildup)
Low severityGDI engines don't get fuel washing the intake valves, so carbon buildup can disrupt sealing/airflow and cause rough running.
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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