P0300 on a 2013 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 2013 Toyota Tacoma
Ranked from 124 NHTSA owner complaints filed for this vehicle.
- 1
Secondary Air Injection System Failure
Medium severityA faulty secondary air pump or stuck switching valve (often accompanied by code P2440) can cause the vehicle to enter limp mode or disrupt the air/fuel mixture, resulting in misfires. Look for damaged air injection valves or pump failure.
Reported in 2 NHTSA complaints - 2
Faulty Valve Springs (Recall 13V557000)
High severityBroken or weak valve springs cause a loss of engine compression and erratic valve operation, leading to severe random misfires. A compression or leak-down test will confirm mechanical valvetrain failure.
Reported in 1 NHTSA complaint - 3
Fuel Delivery / Fuel Pump Issues
High severityFuel starvation causes a lean condition, leading to random misfires across multiple cylinders. Confirm by checking fuel pressure at the rail, especially during cold starts or under load.
Reported in 1 NHTSA complaint - 4
Timing Chain / Tensioner Wear
High severityA stretched timing chain or failing tensioner alters camshaft timing, which can cause random misfires and a rattling noise under load. Confirm by checking camshaft timing marks and inspecting the tensioner.
Reported in 1 NHTSA complaint - 5
Worn Spark Plugs
Low severityWorn electrodes or incorrect spark plug gaps cause weak sparks, leading to incomplete combustion and misfires. Inspect spark plugs for wear, fouling, or carbon tracking.
Common cause - 6
Faulty Ignition Coils
Medium severityDegraded ignition coils fail to provide enough voltage to the spark plugs under load. Confirm by checking for carbon tracking on the coil boots or observing misfire counters on a scan tool.
Common cause - 7
Vacuum Leaks
Medium severityUnmetered air entering the intake manifold causes a lean air/fuel mixture, resulting in random misfires. Use a smoke machine to check for leaks in vacuum hoses or intake gaskets.
Common cause - 8
Dirty or Faulty Mass Air Flow (MAF) Sensor
Low severityA contaminated MAF sensor inaccurately measures incoming air, causing the ECM to command an incorrect fuel trim. Confirm by checking MAF sensor data on a scan tool and inspecting the sensor wire for dirt.
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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