Engine

P03D0 — Cylinder 6 Combustion Fault (Misfire Detected)

Severity: medium Drive with care, to a shop

What P03D0 means

The engine control unit watches crankshaft speed variations and uses them to detect that cylinder 6 is not burning its air-fuel mixture properly. Normally each cylinder contributes equally: the spark plug ignites the mixture, the injector meters fuel and the engine mechanics provide compression. The code points to a cylinder, not a specific part, so the cause could be ignition, fuel, air or mechanical.

Symptoms

  • Rough idle or engine shaking
  • Loss of power or hesitation on acceleration
  • Check engine light on or flashing
  • Increased fuel consumption
  • Vibration at idle or under load
  • Fuel smell from the exhaust

Possible causes

  1. Worn or faulty spark plug in cylinder 6
  2. Failing ignition coil or plug wire on cylinder 6
  3. Clogged or faulty fuel injector on cylinder 6
  4. Low compression: worn rings, burnt valve or head gasket leak
  5. Vacuum or intake air leak near cylinder 6
  6. Damaged wiring or poor connector contact at the coil or injector

How to diagnose

  1. Read all codes and freeze frame data and look for other misfire codes (P0300, P0306, etc.)
  2. Inspect the cylinder 6 spark plug for wear, deposits, oil or a cracked insulator
  3. Swap the cylinder 6 coil with a neighbor and see whether the misfire follows
  4. Check the coil and injector connectors and wiring, and test power and control signals
  5. Test injector operation and resistance, and listen for clicking with a stethoscope
  6. Inspect the intake and vacuum hoses for leaks and review fuel trim values
  7. Run a compression or leak-down test once ignition and fuel are ruled out

Common fixes

  • Replace the spark plugs, ideally as a full set
  • Replace the cylinder 6 ignition coil
  • Clean or replace the cylinder 6 fuel injector
  • Repair vacuum or intake leaks and replace damaged hoses or gaskets
  • Repair the wiring or connector
  • Repair the engine: valves, piston rings or head gasket

Questions and answers

What does P03D0 mean?

It means the ECU detected poor combustion in cylinder 6. The most common causes are a bad spark plug or coil, and less often an injector or mechanical problem.

Can I drive with code P03D0?

Only briefly and under light load. Extended driving with a misfire can ruin the catalytic converter, and a flashing check engine light means you should stop.

How can I quickly find the cause of the cylinder 6 misfire?

Swap the coil and plug with those from another cylinder and clear the code. If the misfire moves, the swapped part is bad; if it stays on cylinder 6, check the 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.