P0300 on a 2019 Toyota Tacoma
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 2019 Toyota Tacoma
Ranked from 210 NHTSA owner complaints filed for this vehicle.
- 1
Low-Pressure Fuel Pump Failure
High severityA known recall issue on this vehicle where the low-pressure fuel pump fails, causing fuel starvation, lean running conditions, and random misfires. Confirmed by checking fuel pressure and verifying if the vehicle is included in the fuel pump recall.
Reported in 6 NHTSA complaints - 2
Valvetrain / Lifter Issues
High severitySticking or failing lifters can prevent valves from opening or closing properly, leading to misfires. Confirmed by listening for abnormal engine ticking noises and physically inspecting the valvetrain components.
Reported in 3 NHTSA complaints - 3
Faulty Fuel Injectors
Medium severityFuel injectors can fail or run rich/lean, causing poor combustion and misfires in specific or random cylinders. Confirmed by performing an injector balance test or checking fuel trim data.
Reported in 2 NHTSA complaints - 4
Internal Engine Damage / Low Compression
High severityDamaged valves or wrist pins can cause a severe loss of cylinder compression, resulting in a dead miss or random misfires. Confirmed by performing a cylinder compression test and a leak-down test.
Reported in 2 NHTSA complaints - 5
Faulty Ignition Coils
Medium severityIgnition coils can degrade over time, failing to provide a strong enough spark to ignite the air/fuel mixture. Confirmed by swapping the suspected coil to another cylinder to see if the misfire follows.
Common cause - 6
Worn Spark Plugs
Low severitySpark plugs with worn electrodes or incorrect gaps will cause weak sparks and incomplete combustion. Confirmed by removing the spark plugs and visually inspecting their condition.
Common cause - 7
Intake Manifold Vacuum Leak
Medium severityUnmetered air entering the engine bypasses the MAF sensor, causing a lean condition that leads to random misfires across multiple cylinders. Confirmed by performing a smoke test on the intake system.
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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