P0301 on Lexus
Cylinder 1 Misfire Detected
P0301 on Lexus vehicles indicates cylinder 1 misfire detected. Au7o has documented this code across 5 Lexus models — most commonly on GS, IS, NX. P0301 means the engine computer detected a misfire specifically in cylinder 1 — the spark didn't ignite the fuel properly, or the fuel/air mix didn't burn as it should. The computer detects this by sensing tiny variations in crankshaft speed each time a cylinder fires. A misfire wastes fuel, raises emissions, and can damage the catalytic converter if it's severe or persistent (a flashing check engine light usually warns of active, converter-damaging misfires). Because the code points to one specific cylinder, the cause is usually an ignition, fuel, or compression problem isolated to that cylinder. Typical repair costs on Lexus range from $80 to $1,000, depending on the specific model and root cause.
Common Causes of P0301
- •Worn or fouled spark plug in cylinder 1
- •Failed ignition coil or coil pack for cylinder 1
- •Faulty or clogged fuel injector for cylinder 1
- •Vacuum or intake air leak affecting that cylinder
- •Bad spark plug wire (on applicable engines)
- •Low compression (worn rings, leaking or burnt valve, head gasket)
- •Carbon buildup on intake valves
- •Wiring or connector fault to the coil or injector
P0301 on Lexus by Model
Lexus GS(1 issue)
- Engine Valve Spring Fracture from Contaminated Spring Material (Recall 10V309000)2007-2008
Valve springs installed in certain 2007-2008 GS 350 / GS 450h and 2008 GS 460 engines were contaminated during manufacturing with micro foreign objects in the spring wire. The contamination creates a stress riser; over time the spring develops a crack and can break outright. A broken valve spring drops the valve out of control, producing immediate ticking/knocking and rough running, and in the worst case the engine fails and stops suddenly while the car is moving. This affected both the 2GR-FSE V6 (GS 350 / GS 450h) and the 1UR-FSE V8 (GS 460) built in the same period - it is a supplier/material defect, not a design fault of one engine, which is why it spans two different engine families. It does NOT apply to the S160 (1998-2005) cars or to the 2013-2020 L10 generation.
Lexus IS(2 issues)
- Carbon Buildup on Intake Valves (2.0T)2016-2022
The direct-injected 2.0L turbo four-cylinder in the IS200t/IS300 accumulates heavy carbon deposits on the intake valves since fuel is not sprayed over the valves to clean them. This leads to rough idle, hesitation under acceleration, and reduced power output typically between 40,000-80,000 miles.
- Valve Cover Gasket Leaks Causing Oil Smell and Misfire Risk2001-2005
Aging valve cover gaskets on the 2JZ-GE commonly harden and leak, allowing oil to seep onto the cylinder head, spark plug tube seals, and exhaust side of the engine. Owners often notice a burnt-oil smell, visible oil around the valve covers, and occasional misfires if oil contaminates ignition components. This is one of the most common age-related engine leaks on the first-gen IS300.
Lexus NX(1 issue)
- Intake Valve Carbon Deposits on the 8AR-FTS Turbo Beyond 60,000 Miles2015-2021
The 8AR-FTS 2.0 turbo in the NX 200t and NX 300 is a direct-injected engine, and Lexus direct-injection engines have a long-standing record of fouling intake valves with carbon because fuel never washes across the back of the valve. Lexus partially mitigated this on the 8AR-FTS with D-4S dual injection - a secondary set of port injectors that does spray the intake valves - which is why this engine is markedly better than a direct-injection-only design and why deposits show up later rather than early. It is not eliminated, however: NX owners posting valve inspections past roughly 60,000 miles document meaningful carbon accumulation on the intake valves, and the symptom set is the classic one - rough cold idle, misfires, hesitation and a check engine light. Buyers of higher-mileage AZ10 NX 200t/300 cars should treat this as an inspection item, not an assumption of failure. This is specific to the 8AR-FTS; the NX 300h hybrid's 2AR-FXE and the second-generation engines are not the same case.
Lexus RC(1 issue)
- Carbon Buildup on Intake Valves (2.0T)2016-2022
The direct-injected 2.0L turbo in the RC200t and RC300 accumulates carbon deposits on the intake valves identically to the IS with the same engine. Without port injection to wash the valves, carbon buildup causes progressive performance degradation starting around 40,000 miles.
Lexus SC300(1 issue)
- Distributor Cap & Rotor Cracking / Ignition Misfire (Non-VVT-i 1992-1997)1992-1997
Pre-VVT-i 2JZ-GE SC300s (1992-1997) use a cam-driven distributor. With age the cap and rotor crack; spark then jumps through the crack, burning a hole in the rotor and causing misfires, rough cold idle, and shaking at idle. A leaking valve-cover gasket that lets oil pool in the spark-plug tubes produces overlapping misfire symptoms, so both should be inspected together. (The 1998-2000 VVT-i engine is distributorless with individual coils, so this applies only to the non-VVT-i years.)
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View P0301 across all makes →Frequently Asked Questions
What does P0301 mean on Lexus?▼
P0301 stands for "Cylinder 1 Misfire Detected." P0301 means the engine computer detected a misfire specifically in cylinder 1 — the spark didn't ignite the fuel properly, or the fuel/air mix didn't burn as it should. The computer detects this by sensing tiny variations in crankshaft speed each time a cylinder fires. A misfire wastes fuel, raises emissions, and can damage the catalytic converter if it's severe or persistent (a flashing check engine light usually warns of active, converter-damaging misfires). Because the code points to one specific cylinder, the cause is usually an ignition, fuel, or compression problem isolated to that cylinder. On Lexus specifically, this code is documented across 5 models.
What causes P0301 on Lexus vehicles?▼
Common causes on Lexus: Worn or fouled spark plug in cylinder 1, Failed ignition coil or coil pack for cylinder 1, Faulty or clogged fuel injector for cylinder 1, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire (on applicable engines). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0301 on a Lexus?▼
Repair costs on Lexus range from $80 to $1,000, depending on the specific model and root cause.
Which Lexus models have P0301 documented?▼
Au7o has documented P0301 on 5 Lexus models: GS, IS, NX, RC, SC300.