Fuel and air

P02A4 — Cylinder 3 Fuel Injector Restricted Flow

Severity: medium Drive with care, to a shop

What P02A4 means

The engine control unit monitors fuel trims and cylinder performance. With P02A4 it has concluded that the cylinder 3 injector delivers less fuel than commanded. This is usually a clogged or worn injector, and less often a wiring or fuel supply problem. The result is a lean mixture in that cylinder and possible misfires.

Symptoms

  • Rough idle and vibration
  • Hesitation or stumbling when accelerating
  • Reduced power
  • Higher fuel consumption
  • Check Engine light on or flashing
  • Hard starting, especially when cold

Possible causes

  1. Clogged or dirty cylinder 3 fuel injector
  2. Mechanical or electrical failure inside the injector
  3. Damaged wiring or corroded injector connector
  4. Low fuel pressure from a weak pump or clogged filter
  5. Intake air leak near cylinder 3
  6. Contaminated or poor-quality fuel

How to diagnose

  1. Scan for codes and freeze-frame data, and look for related cylinder 3 misfire codes
  2. Check short- and long-term fuel trims; a lean condition supports the diagnosis
  3. Compare cylinder contribution or run an injector balance test with a scan tool
  4. Inspect the injector connector and harness, then test power and the control signal with a multimeter or scope
  5. Measure injector coil resistance and compare it with neighboring injectors
  6. Test fuel pressure and how well it holds after shutoff
  7. Inspect the intake system for vacuum leaks
  8. Swap the injector with a neighbor; if the code follows, the injector is faulty

Common fixes

  • Have the injector cleaned on a bench or replace it
  • Replace the cylinder 3 fuel injector
  • Repair the wiring or replace the connector
  • Replace the fuel filter or pump if pressure is low
  • Fix any intake air leak

Questions and answers

What does P02A4 mean?

The ECU believes the cylinder 3 injector is letting too little fuel through. It is most often clogged or faulty, but wiring can also be the cause.

Can I drive with code P02A4?

Only briefly and gently, enough to reach a shop. Extended driving on a lean mixture risks overheating the cylinder and ruining the catalytic converter.

Will fuel injector cleaner fix P02A4?

If the cause is light deposits, an additive can sometimes help. For an electrical fault or a heavy clog, you will need professional cleaning or a new injector.

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.