P0300 on a 2017 Nissan Altima
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 2017 Nissan Altima
Ranked from 384 NHTSA owner complaints filed for this vehicle.
- 1
Faulty Oxygen (O2) Sensor
Low severityA bad O2 sensor provides incorrect air/fuel ratio data to the ECM, which can cause lean or rich conditions resulting in misfires. Multiple complaints mention O2 sensor codes (P0130) or replacements.
Reported in 3 NHTSA complaints - 2
Faulty Ignition Coils
Medium severityIgnition coils are a primary cause of random misfires (P0300). A mechanic diagnosed and replaced ignition coils along with spark plugs after engine warning lights illuminated.
Reported in 1 NHTSA complaint - 3
Worn Spark Plugs
Low severitySpark plugs wear out over time and cause misfires. A mechanic determined the spark plugs needed replacement to address engine warning lights.
Reported in 1 NHTSA complaint - 4
Blown Cylinder Head Gasket / Internal Cylinder Failure
High severityCoolant or oil entering the combustion chamber due to a failed head gasket or cylinder failure causes severe misfires. A mechanic diagnosed a failed #4 cylinder head gasket and subsequent cylinder failure.
Reported in 1 NHTSA complaint - 5
Intake Manifold Runner Control (IMRC) Valve/Sensor Failure
Medium severityA stuck or failing swirl/tumble control valve (often triggering P2004) disrupts the air/fuel mixture, leading to rough idle, sputtering, and misfires. The owner noted the valve position sensor on the manifold fails, causing stalling and sluggishness.
Reported in 1 NHTSA complaint - 6
Vacuum Leaks
Low severityUnmetered air entering the intake manifold leans out the air/fuel mixture, causing random misfires across multiple cylinders. Look for cracked hoses or intake gaskets.
Common cause - 7
Low Fuel Pressure / Failing Fuel Pump
Medium severityInsufficient fuel delivery starves the engine, causing lean misfires. Confirmed by testing fuel pressure at the rail.
Common cause - 8
Clogged or Faulty Fuel Injectors
Medium severityDirty or malfunctioning injectors fail to spray the correct amount of fuel, leading to misfires. Confirmed by injector balance testing or flow testing.
Common cause
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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