P0306 on Toyota
Cylinder 6 Misfire Detected
P0306 on Toyota vehicles indicates cylinder 6 misfire detected. Au7o has documented this code across 2 Toyota models — most commonly on GR86, Tacoma. This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. Typical repair costs on Toyota range from $1,500 to $3,500, depending on the specific model and root cause.
Common Causes of P0306
- •Worn or fouled spark plug on cylinder 6
- •Failed ignition coil for cylinder 6
- •Clogged, leaking, or failed fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt valve, head gasket)
- •Damaged plug wire or coil connector
- •Carbon buildup or worn valvetrain components
P0306 on Toyota by Model
Toyota GR86(1 issue)
- Valve Spring Recall - Engine Stall Risk2022-2023
Toyota/Subaru recalled early 2022-2023 GR86 and BRZ models for improperly manufactured valve springs in the FA24 engine. Defective springs can fracture, causing engine misfires, rough running, and potential engine stalling while driving. Recall 22V-879.
Toyota Tacoma(1 issue)
- 1GR-FE 4.0L V6 Head Gasket Failure on Early 2005-2006 Models (Coolant Loss and Cold-Start Misfire)2005-2006
The first model years of the 4.0L 1GR-FE V6 used an early head gasket design whose sealing material between the cylinder and the coolant jacket degrades over time, allowing a small coolant leak into a cylinder. The classic signature is a cold-start misfire on cylinder 4 (and sometimes cylinder 6) that 'steam-cleans' the spark plug, throwing P0304/P0306, together with slow coolant loss from the reservoir (owners report topping off every few weeks) and a gurgling sound from the heater core on startup. Because the leak is small early on, it is frequently misdiagnosed as a bad coil or plug before the head gasket is identified. Left unaddressed it progresses to overheating and possible head/block damage.
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View P0306 across all makes →Frequently Asked Questions
What does P0306 mean on Toyota?▼
P0306 stands for "Cylinder 6 Misfire Detected." This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. On Toyota specifically, this code is documented across 2 models.
What causes P0306 on Toyota vehicles?▼
Common causes on Toyota: Worn or fouled spark plug on cylinder 6, Failed ignition coil for cylinder 6, Clogged, leaking, or failed fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0306 on a Toyota?▼
Repair costs on Toyota range from $1,500 to $3,500, depending on the specific model and root cause.
Which Toyota models have P0306 documented?▼
Au7o has documented P0306 on 2 Toyota models: GR86, Tacoma.