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P0302Cylinder 2 misfire detected

Content reviewed: Content reviewed by a heavy-duty technician. About our editorial approach

OK to drive

— A single-cylinder miss is usually driveable at light throttle, but a flashing check-engine light means raw fuel is reaching the converter — reduce load and repair before the catalyst pays for it.

What does this severity mean?

General guidance only — not a substitute for a professional inspection or official roadside / out-of-service criteria (e.g. CVSA OOSC) in your jurisdiction.

Part of system: Electrical sensing & powertrain inputs · Wire gauge & ampacity tool

Tells you the misfire monitor isolated the fault to cylinder 2 alone, so the job is comparison work rather than a parts hunt. Crankshaft velocity dips at the firing event assigned to that cylinder, which the driver feels as a stumble that comes and goes with load plus a flat spot just off idle. Open Mode $06 or the OEM misfire-count PID and confirm the counts stay on that one hole, then move the cylinder-2 coil and plug to a neighbouring cylinder: if the counts follow the hardware you have an answer in ten minutes. If they stay put, smoke-test that intake runner for a cracked gasket, compare injector resistance and current ramp against a healthy cylinder, and only then measure relative compression. Keep loads light while the light is on.

Parts that may be involved

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Vehicles often affected

Common on high-mileage coil-on-plug four- and six-cylinder engines, and on layouts where cylinder 2 sits under a plenum that makes plug service easy to postpone.

Typical symptoms

  • Stumble that appears and disappears with engine load
  • Rough spot just off idle that smooths out at cruise
  • Misfire counter climbing only on cylinder 2
  • Exhaust note with a repeating soft beat at idle
  • Fuel trim drifting positive on the bank holding cylinder 2

Likely causes

  • Failed ignition coil or carbon-tracked boot on cylinder 2
  • Spark plug in cylinder 2 worn past its gap limit or oil-fouled
  • Cracked intake gasket feeding unmetered air to runner 2
  • Cylinder-2 injector restricted, leaking, or electrically open
  • Mechanical compression loss on cylinder 2 from valve or ring wear

Recommended checks

  1. 1

    Confirm in Mode $06 that the counts sit only on cylinder 2

  2. 2

    Move the cylinder-2 coil and plug to another hole and recheck

  3. 3

    Smoke-test the intake for a leak feeding runner 2 only

  4. 4

    Scope injector current on cylinder 2 against a known-good cylinder

  5. 5

    Finish with relative compression before ordering any parts

DIY vs professional

DIY: swap coil and plug between cylinders, read the plug, run a basic smoke test. Pro: injector current ramps, leak-down testing, and any valvetrain repair.

See also

Related terms

Content reviewed by a heavy-duty technician. About our editorial approach