Engine

P03DA — Cylinder 7 Combustion Performance Fault

Severity: medium Drive with care, to a shop

What P03DA means

The engine control module watches crankshaft speed through the crankshaft position sensor. When cylinder 7 fails to speed the crank up as much as it should after its firing event, the ECM sets P03DA. This is normally a misfire caused by a spark, fuel, air or mechanical problem in that cylinder.

Symptoms

  • Rough idle or engine vibration
  • Loss of power and hesitation on acceleration
  • Check engine light on or flashing
  • Worse fuel economy
  • Stumbling or a misfire feeling
  • Fuel smell from the exhaust

Possible causes

  1. Worn or faulty spark plug in cylinder 7
  2. Failed ignition coil or bad coil connector for cylinder 7
  3. Clogged or failing fuel injector for cylinder 7
  4. Low compression in cylinder 7: valves, rings or head gasket
  5. Vacuum or intake air leak near cylinder 7
  6. Damaged wiring or poor connection at the coil or injector

How to diagnose

  1. Scan all codes and freeze-frame data, and check per-cylinder misfire counters to confirm cylinder 7 is the one misfiring.
  2. Locate cylinder 7 using your engine's cylinder numbering layout.
  3. Inspect the cylinder 7 spark plug for gap, wear, cracks, and oil or fuel fouling.
  4. Swap the cylinder 7 coil with a neighboring one, clear codes and see whether the misfire follows the coil.
  5. Check coil and injector connectors and wiring, measure injector resistance and listen for injector clicking.
  6. Inspect the intake manifold and vacuum hoses for leaks, using a smoke machine if needed.
  7. Run a compression or cylinder leak-down test on cylinder 7.
  8. Check fuel pressure and fuel trim values for a mixture problem.

Common fixes

  • Replace the cylinder 7 spark plug, preferably the full set
  • Replace the cylinder 7 ignition coil
  • Clean or replace the cylinder 7 fuel injector
  • Fix intake leaks by replacing gaskets or hoses
  • Repair internal engine problems such as valves, rings or head gasket
  • Repair damaged wiring or connectors

Questions and answers

What does P03DA mean?

It means poor combustion in cylinder 7, usually a misfire. The cause may be a spark plug, coil, injector, air leak or low compression.

Can I drive with P03DA?

Only briefly and gently. If the check engine light is flashing, do not drive, because the catalytic converter can be damaged quickly.

What is the fastest way to find the cause of P03DA?

Start with the cylinder 7 plug and coil. Swap the coil to another cylinder: if the misfire moves, the coil is bad. If not, 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.