Fuel and air

P02F1 — Cylinder 4 Injector Circuit Range/Performance

Severity: medium Drive with care, to a shop

What P02F1 means

The engine control unit fires the cylinder 4 injector by switching its circuit to ground, and it monitors the current and voltage in that circuit. P02F1 sets when the electrical readings or the injector's response fall outside expected limits. The cause may be the injector itself, its wiring or connector, or, less often, the driver inside the control unit.

Symptoms

  • Check Engine light on
  • Rough idle
  • Loss of power and sluggish acceleration
  • Worse fuel economy
  • Misfire or engine shaking
  • Hard starting

Possible causes

  1. Faulty or clogged cylinder 4 fuel injector
  2. Open or short in the injector wiring
  3. Poor contact, corrosion or damage at the connector
  4. Failed injector driver inside the PCM
  5. Fuel supply problem such as low pressure
  6. Air leak skewing the air-fuel mixture

How to diagnose

  1. Scan all codes and freeze frame data, and look for cylinder 4 misfire codes
  2. Inspect the cylinder 4 injector connector and harness for corrosion, chafing and oil contamination
  3. Measure injector coil resistance and compare it with the other cylinders and the factory spec
  4. Check for power and the control signal at the connector with a noid light or scope
  5. Test the wire from the connector to the PCM for opens and shorts to ground or voltage
  6. Review fuel trims and cylinder balance data
  7. Check fuel pressure and inspect the intake for vacuum leaks
  8. If wiring and injector test good, evaluate the PCM or have a specialist do it

Common fixes

  • Replace, or clean and flow-test, the cylinder 4 injector
  • Repair the wiring or replace the damaged connector
  • Fix the vacuum leak or fuel pressure problem
  • Repair or replace the PCM if the driver is confirmed faulty

Questions and answers

What does P02F1 mean?

It's a cylinder 4 injector circuit fault: the circuit's electrical values or the injector's operation are outside the expected range. The injector, wiring or connector is most often to blame.

Can I drive with code P02F1?

Only briefly and carefully, to get it repaired. If the engine is misfiring, avoid driving, since the catalytic converter can overheat and the engine may wear faster.

How do I tell a bad injector from a wiring problem?

Measure the injector's resistance and test the wires back to the PCM. You can also swap the injector with a neighboring cylinder's: if the fault follows to the other cylinder, the injector is bad.

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.