P0301 indicates a misfire in cylinder 1. Overall repair costs typically range from about $150 to $600, depending on the underlying cause and the vehicle. The exact price depends on which component is faulty and how much labor is required.
This article explains what P0301 means, the common causes behind a cylinder 1 misfire, and the typical cost ranges you can expect from repair shops. Costs can vary widely by make, model, and region, so use these figures as a framework rather than a firm quote.
What P0301 means
P0301 is a generic diagnostic trouble code that signals a misfire in the first cylinder of the engine. A misfire occurs when the air-fuel mixture in a cylinder fails to ignite properly or at all, which can cause rough running, hesitations, reduced power, and increased emissions. Fixing P0301 starts with accurate diagnosis to identify the exact cause in cylinder 1.
Common causes of P0301
Misfires in cylinder 1 can originate from several different parts or conditions. The following list covers the most frequent culprits that technicians encounter when diagnosing P0301.
- Worn or damaged spark plug on cylinder 1
- Defective ignition coil or coil-on-plug for cylinder 1
- C clogged or leaking fuel injector for cylinder 1
- Vacuum leak or intake manifold leak affecting cylinder 1
- Faulty wiring or connector to the coil or injector
- Low or inconsistent fuel pressure
- Internal engine problems such as low compression (less common)
Diagnosing the exact cause is essential because the recommended repair varies widely depending on which component is at fault. A prudent shop will confirm the diagnosis with tests before replacing parts.
Cost breakdown: typical price ranges
Costs can vary widely by vehicle and location. The ranges below reflect common scenarios across many shops in the United States as of 2024–2026. Some shops charge a diagnostic fee regardless of the repair, and some apply it toward the final bill if you proceed with the repair.
- Diagnostic fee to identify the misfire and rule out related problems — typically $80 to $150. Some shops waive or credit this if you proceed with repairs.
- Spark plug replacement for cylinder 1 — parts and labor generally $100 to $300, depending on the plug type and engine design.
- Ignition coil replacement for cylinder 1 — $120 to $350 for the part, plus 1 hour or more of labor; total often $200 to $600 if a coil is bad on a modern coil-on-plug setup.
- Fuel injector servicing or replacement for cylinder 1 — injector cleaning may be $50 to $150; replacement injector could be $250 to $700 per injector, plus labor.
- Vacuum leak repair (manifold gasket, hoses) — typically $100 to $300, depending on location and parts.
- Internal engine issues or compression problems (less common) — major repairs such as head gasket or piston work can run well over $1,000, often several thousand, depending on engine design and labor.
- Electrical/wiring or sensor issues (corrosion, connectors) — $50 to $200 for parts, plus labor to diagnose and fix.
When you add up the potential parts and labor, a straightforward spark plug or coil issue tends to stay on the lower end of the spectrum, while injector problems or mechanical failures push the price higher. Diagnostic timing, vehicle type, and regional labor rates all influence the final bill.
What to expect at the shop
Most shops start with a diagnostic scan, road test, and visual inspection of ignition components. They may perform compression tests or leak-down tests if a mechanical problem is suspected. Request a detailed, itemized estimate before work begins, and ask whether the diagnostic fee will be applied to the final bill if you proceed with repairs.
Summary
P0301 signifies a misfire in cylinder 1. Costs to fix vary widely—from a few hundred dollars for simple ignition or spark plug issues to several thousand for major mechanical problems. A precise diagnosis is key to avoiding unnecessary parts replacement, and getting multiple estimates can help you compare labor and parts pricing across shops.