Fuel and air

P02A9 — Cylinder 4 Fuel Injector Leaking

Severity: medium Drive with care, to a shop

What P02A9 means

The engine control module detected that the cylinder 4 injector is letting fuel through when it should be closed, or delivering more than commanded. An injector normally opens on a short electrical pulse and seals tightly between injections. A worn needle or seal lets extra fuel into the cylinder, enriching the mixture, and this can show up as fuel trim shifts or rail pressure that bleeds down.

Symptoms

  • Rough idle or engine shaking
  • Poor fuel economy
  • Check engine light on
  • Misfire on cylinder 4
  • Long cranking or hard hot start
  • Fuel smell in the engine bay or exhaust
  • Hesitation and loss of power

Possible causes

  1. Worn or internally leaking cylinder 4 fuel injector
  2. Damaged injector O-rings or seals
  3. Contaminated or poor-quality fuel keeping the injector from sealing
  4. High fuel pressure from a faulty regulator or sensor
  5. Damaged injector wiring or connector, or a short to ground or power
  6. Air leak skewing the mixture and fuel trim readings
  7. Rarely, an ECM or injector driver fault

How to diagnose

  1. Scan for codes and freeze frame data, and look for related misfire codes such as P0304 or mixture codes
  2. Review short and long term fuel trims and compare with other cylinders
  3. Inspect the cylinder 4 injector connector and harness for corrosion, chafing and fuel residue
  4. Measure injector coil resistance and compare it with spec and neighboring injectors
  5. Test fuel rail pressure and how fast it drops after shutdown
  6. Run a cylinder balance or injector cutout test with a scan tool
  7. Pull the cylinder 4 spark plug and check for sooting or fuel wetness
  8. Check for intake and exhaust leaks

Common fixes

  • Replace the leaking cylinder 4 injector along with new seals
  • Repair or replace damaged injector wiring or connector
  • Clean or bench test the injector if contamination is minor
  • Replace a faulty fuel pressure regulator or sensor
  • Replace bad fuel and the filter, and change the oil if it is diluted with fuel

Questions and answers

What does P02A9 mean?

The ECM believes the cylinder 4 injector is leaking or delivering too much fuel. The injector itself is the most common cause, followed by wiring or fuel pressure problems.

Can I drive with code P02A9?

Only for a short trip, such as to a shop. Long-term driving risks oil dilution, misfires and a damaged catalytic converter.

Will injector cleaner fix it?

Only if the problem is light contamination. A worn injector that no longer seals needs to be replaced.

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.