Code
P02F1
Generic
P — Powertrain
Cylinder 4 Injector Circuit Range/Performance
AI status
Completed
Completed
100%
Causes
- Faulty or stuck fuel injector (mechanical or internal electrical fault)
- Open, shorted or high-resistance wiring in injector circuit
- Poor connector contact/corrosion at injector or harness
- Faulty injector driver in ECM or dedicated injector control module
- Low or inconsistent fuel rail pressure or clogged fuel supply
- Fuel contamination (debris, varnish) restricting injector flow
Symptoms
- MIL/Check Engine Lamp illuminated
- Rough idle or vibration, particularly at idle
- Loss of power, hesitation or poor acceleration
- Increased fuel consumption
- Misfire on cylinder 4 (may store misfire codes P0304)
- Intermittent performance issues under load or at idle
What to check
- Retrieve freeze-frame and live data with a scan tool; note conditions when code set
- Visual inspection of injector wiring, boots and connector for damage or corrosion
- Check for related codes (misfire, fuel pressure, communication errors)
- Measure injector resistance with ohmmeter and compare to spec
- Backprobe injector connector to check battery voltage and ground/pulse while cranking/running
- Compare injector pulse width and activity against another cylinder using a scan tool or oscilloscope
Signal parameters
- Injector supply voltage: approx. battery voltage (typically ~9–14 V depending on vehicle)
- Injector driver: ECM switches ground or positive to modulate injector current (varies by system)
- Typical injector coil resistance: commonly low-impedance ~2–4 Ω or high-impedance ~10–16 Ω — consult vehicle spec
- Typical injector pulse width: from
- Correct waveform: clean square/triangular pulse on scope with consistent amplitude and timing relative to other cylinders
- Fault indicators: open circuit (infinite Ω), short to ground/voltage (very low Ω), erratic/no pulse on scope
Diagnostic algorithm
- Read and record all DTCs and freeze-frame data. Note engine conditions (temp, RPM, load) when code set.
- Clear codes, perform road/test or replicate conditions to see if code returns.
- Visually inspect cylinder 4 injector connector and wiring for damage, corrosion, rodent chewing, or pin back-out.
- Measure injector coil resistance at the connector with ignition off; compare to specification. Replace if out of range.
- With backprobe, verify battery voltage at the injector supply pin with ignition ON. Voltage should be present and stable.
- Start engine (or crank) and backprobe driver side to confirm ECM is pulsing the injector. Use a scan tool or oscilloscope to view pulse width and waveform; compare to a known-good cylinder.
Likely causes
- Failed or partially blocked cylinder 4 injector
- Wiring harness damage or poor connector/terminal contact at cylinder 4
- Faulty injector driver on the ECM
- Low fuel pressure or contaminated fuel affecting cylinder 4 operation
Fault status
Status
P02F1 — Cylinder 4 Injector Circuit Range/Performance detected. Inspect injector, wiring, fuel supply, and ECM driver.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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