P0302 — Cylinder 2 Misfire Detected

OBD2 code P0302 flags a problem with the engine misfire monitoring (cylinder 2 misfire detected). Short, gentle driving to a shop is usually possible. Common culprits: faulty crankshaft/camshaft position signal, worn or fouled spark plugs, failed ignition coil or coil wiring.

powertrain (engine/transmission)

Is it safe to drive?

Diagnose P0302 promptly A mild P0302 misfire may allow short trips, but continued driving can damage the catalytic converter or exhaust components. Avoid extended driving or hard acceleration if the engine is shaking severely, losing power, or producing a strong fuel odor.

Typical symptoms

  • The check-engine light may illuminate with P0302 stored in the powertrain controller
  • The engine may run rough, shake, or stumble at idle
  • Acceleration may feel weak or uneven
  • A burning odor may come from unburned fuel during a sustained P0302 misfire
  • Fuel economy may decrease while the cylinder repeatedly fails to burn

Common causes

  • A weak or failed ignition coil on cylinder 2
  • A worn, fouled, or defective spark plug in cylinder 2
  • A clogged or leaking fuel injector on cylinder 2
  • Low cylinder compression caused by a damaged valve, piston, or head gasket
  • Corroded ignition wiring, a loose connector, or an open circuit affecting cylinder 2
  • An exhaust or emissions-system restriction that makes the misfire appear more pronounced

How to diagnose with an OBD scanner

  1. Confirm the P0302 misfire Connect an OBD2 scanner, such as an ELM327 adapter used with AIScanAuto, and confirm whether P0302 is active, pending, or historical. Save freeze-frame data and review the cylinder-misfire counters before clearing any codes.
  2. Inspect cylinder 2 ignition With the engine off, inspect the cylinder 2 spark plug, ignition coil, plug wires or coil connectors, and related wiring. Look for cracks, oil contamination, carbon fouling, corrosion, heat damage, or a connector that is not fully seated.
  3. Perform an ignition comparison If the engine layout permits it, a technician can compare the cylinder 2 coil and spark plug with an adjacent cylinder. A coil that works on another cylinder but produces a weak or absent signal on cylinder 2 strongly identifies that component as faulty.
  4. Check fuel delivery and compression A technician should check fuel pressure and perform an injector balance or drop test on cylinder 2. If the injector passes, a compression and leak-down test can reveal a damaged valve, piston, gasket, or other low-compression condition.
  5. Repair, clear, and verify Replace the confirmed failed component, clear the P0302 code with the scanner, and road-test the vehicle while watching the misfire counters. P0302 should remain inactive and the cylinder 2 counter should stop increasing if the repair is successful.

Approximate repair cost

Typical independent-shop estimates for diagnosing and repairing P0302 are roughly $150-$1,800, depending on whether the cause is a spark plug, ignition coil, injector, or internal engine fault. Labor, parts, and complexity vary by vehicle. These figures are estimates only and vary by region.

Common questions

What does P0302 specifically mean?

P0302 means the powertrain controller detected a repeated combustion misfire in cylinder 2, so that cylinder is not burning fuel as intended.

Is it safe to drive with P0302 active?

Brief driving may be possible if the misfire is mild, but severe shaking, power loss, or fuel odor calls for stopping and diagnosis to limit catalyst damage.

Should P0302 be cleared before replacing parts?

Do not clear the code first. Save its freeze-frame data and misfire counters, then test cylinder 2 and confirm the failed component before clearing it.

What is the most common cause of P0302?

A weak ignition coil or worn spark plug on cylinder 2 is common, although injector, wiring, and low-compression faults can also produce the same code.

When your engine control unit detects that one of the cylinders isn't firing properly, it logs a specific fault code to help you track down the problem. P0302 specifically points to cylinder number two — the second cylinder in the firing order isn't delivering the combustion event the ECU expects. This falls under the powertrain category, meaning it affects the engine itself and its immediate supporting systems.

Modern engines rely on continuous monitoring through the misfire detection system. The control module watches for irregularities in crankshaft rotation speed — each power stroke should accelerate the crank by a predictable amount. When cylinder 2 fails to fire, that acceleration is missing, and the ECU flags it. The system doesn't just log the code once and forget it; it typically needs to see the problem occur across multiple driving cycles before confirming the fault. It also saves a freeze frame — a snapshot of rpm, engine load, coolant temperature, and vehicle speed at the exact moment the misfire happened. That snapshot is gold when you're trying to figure out what conditions caused the problem.

Common Symptoms of P0302

  • Check Engine Light is on, and it may flash if the misfire is severe
  • Rough idle — the engine shakes or vibrates more than normal
  • Hesitation or stumbling when you press the gas pedal
  • Noticeable loss of power during acceleration
  • Unburned fuel smell coming from the exhaust
  • Fuel economy drops — you're filling up more often than usual

Common Causes of P0302

  • Worn, fouled, or incorrectly gapped spark plugs
  • Faulty ignition coil or coil boot on cylinder 2
  • Clogged or leaking fuel injector serving cylinder 2
  • Vacuum leak in the intake manifold or intake hoses near cylinder 2
  • Low compression in cylinder 2 from worn rings, bad valves, or head gasket failure
  • Weak fuel pump or restricted fuel pressure affecting that cylinder's supply

How to Diagnose P0302

  1. Plug in an OBD2 scanner and pull all stored codes. Record P0302 and the freeze frame data — it tells you what the engine was doing when the fault was detected.
  2. Look for any related codes. Fuel pressure codes, oxygen sensor codes, or other misfire codes often point to the real culprit. Also check for manufacturer technical service bulletins on your specific make and model — there may be a known issue or software update.
  3. Inspect the cylinder 2 ignition components first. Pull the coil and check the boot for cracks, carbon tracking, or moisture. Look at the spark plug — is it fouled, wet, or gap-worn?
  4. Examine the wiring harness and connector going to cylinder 2's injector and coil. Damaged wires, corrosion, or loose pins will cause intermittent or complete failures.
  5. Check fuel injector operation — you can test resistance with a multimeter or use a noid light to verify the injector is pulsing. Inspect the injector harness for chafing.
  6. If the fuel and ignition systems check out, perform a compression test on cylinder 2. Low compression compared to the other cylinders points to mechanical damage inside the engine.

Repair Options and Costs

Spark plug replacement on a four-cylinder typically runs $90 to $250 including parts and labor. Ignition coils vary by vehicle — expect $150 to $380 per coil. Cleaning a fuel injector is cheaper than replacing it, running $200 to $300, while a full injector replacement including labor lands around $400 to $600. If the problem turns out to be mechanical — low compression, head gasket, or internal damage — engine work can cost $800 to $2,500 depending on what's wrong and whether the engine needs to come out.

How Much Does Fixing P0302 Cost Overall?

Tackling P0302 typically falls somewhere between $90 and $2,500. The wide range reflects how different the underlying causes can be. Most of the time you're dealing with ignition or fuel delivery components, which land on the lower end of that spectrum. Always diagnose before you buy parts — throwing expensive components at a misfire without knowing the root cause rarely ends well, and the cheapest fix is seldom the right first step.

Can You Drive with P0302?

Proceed with caution. A flashing Check Engine Light alongside P0302 indicates an active misfire, which pushes raw fuel into the exhaust and can destroy your catalytic converter in a matter of miles. If the light is flashing, pull over and have the vehicle towed. If the light is steady, you can drive a short distance to a repair shop — keep the load light, avoid high speeds, and don't ignore it. The risk isn't just the misfire itself; it's what unburned fuel does to your emissions system downstream.

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