Faulty or sticking cylinder 4 fuel injector (internal electrical or mechanical fault); Damaged, chafed or corroded wiring between the engine control unit and the cylinder 4 injector; Poor connection at the injector plug or control unit connector (loose, corroded or spread terminals); Low or unstable supply voltage to the injector circuit, such as a weak battery or poor earth; Fuel pressure problem affecting injector response on that cylinder, depending on the fuel system type; Fault in the injector driver stage inside the engine control unit.

P02F1

Cylinder 4 Injector Circuit Range/Performance.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
2: AreaFuel and air metering (injector circuit)
F1: FaultThe specific fault in that area

What it means

P02F1 is a generic powertrain code meaning the engine control unit has found the cylinder 4 fuel injector circuit is not performing as expected. The control unit monitors the injector driver and its feedback, and it set this code because the electrical behaviour or the injector response fell outside the expected range, without necessarily being a full open or short circuit. The exact monitoring strategy and thresholds vary by manufacturer and engine.

Symptoms

Engine misfire or rough running, especially at idle
Hesitation or reduced power under load
Raised fuel consumption
Engine warning light on, possibly flashing during a misfire
Hard starting or extended cranking
Fuel smell or black smoke from the exhaust in some cases

Possible causes

Faulty or sticking cylinder 4 fuel injector (internal electrical or mechanical fault)likely
Damaged, chafed or corroded wiring between the engine control unit and the cylinder 4 injectorlikely
Poor connection at the injector plug or control unit connector (loose, corroded or spread terminals)likely
Low or unstable supply voltage to the injector circuit, such as a weak battery or poor earthpossible
Fuel pressure problem affecting injector response on that cylinder, depending on the fuel system typepossible
Fault in the injector driver stage inside the engine control unitrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine load, temperature and rpm when the fault set, and check for related misfire or other injector codes
Check for relevant technical service bulletins and any control unit software updates for the model and engine
Visually inspect the cylinder 4 injector connector and wiring for chafing, heat damage, water ingress and corrosion
Check battery condition, charging voltage and the main engine earths for good connections
Check live data for cylinder 4 misfire counts and fuel trims, and compare with the other cylinders
Test the injector circuit for resistance, supply and earth or driver signal at the connector using a multimeter or oscilloscope, following the manufacturer's specifications
Compare the cylinder 4 injector's resistance and electrical waveform with a known good cylinder, or perform an injector balance or leak-down test as the engine type allows
Check fuel pressure against specification, as the method depends on whether the engine is port or direct injection

How to fix

Repair or replace damaged wiring, and clean or renew faulty connector terminals
Replace the cylinder 4 injector if it fails electrical or flow tests, following the correct procedure for the engine type
Restore good battery condition, charging output and earth connections
Correct any fuel pressure fault found, such as a faulty pump, regulator or pressure sensor, as appropriate to the model
Update the engine control unit software only if the manufacturer lists it as a fix for this fault, and replace the unit only after all else is ruled out

Can I keep driving?

Medium severity

Short, gentle driving is usually possible, but get it checked soon. A misfiring or leaking injector can damage the catalytic converter and, in severe cases, the engine, so stop driving if the warning light flashes or the engine runs very roughly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.