P0300 on a 2015 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 2015 Nissan Altima

Ranked from 941 NHTSA owner complaints filed for this vehicle.

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1
Faulty Mass Air Flow (MAF) Sensor
Medium severity
A failing MAF sensor can cause incorrect air/fuel mixture calculations, leading to stalling, hesitation, and random misfires. Look for stalling at speed or hesitation, often accompanied by MAF-specific codes alongside P0300.
Reported in 2 NHTSA complaints
2
Leaking Valve Cover Gasket / Oil in Spark Plug Tubes
Medium severity
Oil leaking past the valve cover gasket into the spark plug tubes can foul the ignition coils and spark plugs, causing random misfires and stalling. Inspect the spark plug wells for oil accumulation.
Reported in 2 NHTSA complaints
3
Failing Variable Valve Timing (VVT) Solenoid / Valve
Medium severity
A malfunctioning VVT valve can disrupt engine timing, causing rough idling, stalling at low speeds, and random misfires. Check for stalling when coming to a stop and VVT-related codes.
Reported in 1 NHTSA complaint
4
Faulty Crankshaft Position Sensor
High severity
A failing crankshaft position sensor can cause the engine to shut off randomly without warning and cause misfires by losing the engine's timing signal. Look for sudden stalling while driving.
Reported in 1 NHTSA complaint
5
Worn or Failing Timing Chain
High severity
A stretched or failing timing chain alters engine timing, leading to misfires, loss of power, and potential engine failure. Listen for rattling noises from the engine cover and check for timing correlation codes.
Reported in 1 NHTSA complaint
6
Exhaust Manifold Leak
Low severity
An exhaust leak near the manifold can introduce unmetered oxygen to the upstream O2 sensor, causing the engine to run lean and misfire. Listen for ticking noises from the engine bay that get louder under acceleration.
Reported in 1 NHTSA complaint
7
Worn Spark Plugs
Low severity
Worn or fouled spark plugs fail to ignite the air/fuel mixture consistently, causing random misfires. Inspect spark plugs for wear, carbon buildup, or incorrect gap.
Common cause
8
Failing Ignition Coils
Medium severity
Weak or failing ignition coils cannot provide enough voltage to spark plugs, leading to misfires under load. Test coils for proper resistance and check for carbon tracking.
Common cause
9
Vacuum Leaks
Medium severity
Unmetered air entering the intake manifold leans out the air/fuel mixture, causing random misfires, especially at idle. Perform a smoke test to locate leaks in hoses or intake gaskets.
Common cause
10
Low Fuel Pressure / Failing Fuel Pump
High severity
Inadequate fuel pressure starves the engine of fuel, causing a lean condition and random misfires across multiple cylinders. Test fuel pressure at the rail with a mechanical gauge.
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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Matching symptoms

Car Runs Rough Flashing Check Engine Light