Ignition

P0302 — Cylinder 2 Misfire Detected

Severity: medium Drive with care, to a shop

What P0302 means

The engine control unit watches crankshaft speed and detects when cylinder 2 is not burning its air-fuel mixture properly. A cylinder needs spark, the right amount of fuel, good compression and correct airflow to fire. If any of these fails on cylinder 2, the ECU sets P0302.

Symptoms

  • Check engine light on or flashing
  • Rough, shaky idle
  • Engine vibration
  • Hesitation and power loss when accelerating or under load
  • Worse fuel economy
  • Fuel smell from the exhaust
  • Occasional stalling

Possible causes

  1. Worn or faulty spark plug in cylinder 2
  2. Failed ignition coil or coil wiring on cylinder 2
  3. Clogged or leaking fuel injector on cylinder 2
  4. Vacuum leak near the cylinder 2 intake runner (manifold gasket, cracked hose)
  5. Low compression: valve, piston rings or head gasket
  6. Damaged wiring or connector at the coil or injector
  7. Less commonly, sensor or valve timing problems

How to diagnose

  1. Scan for codes and freeze frame data, and check for other misfire or fuel trim codes
  2. View per-cylinder misfire counters if your scan tool supports them
  3. Inspect the cylinder 2 spark plug for wear, deposits, oil, cracks and gap
  4. Check the coil and injector connectors and wiring
  5. Swap the cylinder 2 coil (and plug) with a neighbor, clear codes and see if the misfire follows
  6. Test the injector: listen for clicking, check resistance and compare cylinder balance
  7. Look for vacuum leaks at hoses and the intake manifold gasket
  8. If electrical and fuel checks pass, do a compression test and a leak-down test if needed

Common fixes

  • Replace spark plugs, ideally as a full set
  • Replace the cylinder 2 ignition coil
  • Clean or replace the cylinder 2 fuel injector
  • Fix vacuum leaks by replacing the gasket or hose
  • Repair the engine for low compression (valves, rings, head gasket)
  • Repair damaged wiring or connectors

Questions and answers

What does P0302 mean?

It means the ECU detected a misfire in cylinder 2. The usual culprits are the spark plug or ignition coil, followed by the injector, a vacuum leak or internal engine wear.

Can I drive with a P0302 code?

Brief, light-load driving is possible, but avoid long trips. Misfires can damage the catalytic converter, and with a flashing check engine light you should avoid driving unless absolutely necessary.

How do I find the cause of P0302 quickly?

Swap the cylinder 2 coil with another cylinder's coil, clear the code and drive. If the misfire moves, the coil is bad. If not, check the plug, injector and compression.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.