P0300 on a 2020 Toyota Rav4

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 2020 Toyota Rav4

Ranked from 627 NHTSA owner complaints filed for this vehicle.

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1
Coolant intrusion into the engine from the known coolant bypass valve/engine defect
High severity
This vehicle is covered by NHTSA Campaign 20V064000 for a defective engine coolant bypass valve that leaks coolant into the engine; several owners report coolant intrusion diagnosed by the dealer, engine replacement, and white smoke/rough running on startup - coolant reaching the cylinders directly causes misfire.
Reported in 4 NHTSA complaints
2
Water pump failure secondary to the coolant bypass valve defect
High severity
One owner's water pump suddenly and completely failed shortly after a coolant bypass valve repair, with the mechanic linking the two failures - a sudden loss of coolant circulation and pressure can quickly lead to overheating-related misfire.
Reported in 1 NHTSA complaint
Parts:water pump
3
Weak or failing fuel pump
High severity
One owner's engine stalled and would not restart while fueling, and the dealer diagnosed a fuel pump failure - inadequate fuel delivery causes misfire before it stalls the engine outright.
Reported in 1 NHTSA complaint
Parts:fuel pump
4
Low fuel pressure sensor fault (hybrid fuel system)
Medium severity
One owner had the low fuel pressure sensor replaced after a hybrid-system malfunction with power loss and jerking on the highway; an inaccurate fuel pressure reading can cause the fuel system to under- or over-deliver fuel, producing a misfire.
Reported in 1 NHTSA complaint
Parts:fuel pressure sensor
5
Worn or fouled spark plugs
Medium severity
Eroded electrodes or carbon fouling widen or foul the spark gap, causing intermittent misfire.
Common cause
Parts:spark plugs
6
Failing ignition coil(s)
Medium severity
A weak or intermittently shorting coil misfires its cylinder, often worse when hot or under load.
Common cause
Parts:ignition coil
7
Carbon buildup on intake valves
Low severity
Direct-injection engines lack port-injection fuel wash over the valves, allowing carbon to build up and disrupt airflow/mixture at the valve.
Common cause
8
Clogged or leaking fuel injector(s)
Low severity
A partially clogged or leaking injector under- or over-fuels its cylinder, producing a misfire on that cylinder specifically.
Common cause
Parts:fuel injector

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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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Matching symptoms

Car Runs Rough Flashing Check Engine Light