P02F1: injector 4 current takes too long or too little time to fall

P02F1 evaluates the end-of-injection current decay for cylinder 4 in the documented GM monitor. It measures the time for injector current to fall from the hold or bypass level to zero.

Both ends of the timing range matter

The listed fault boundaries are above 24 microseconds or below 7 microseconds. A range/performance result can therefore reflect a decay that is too slow or too fast; the code alone does not identify which boundary was crossed.

The source describes possible injector or ECU faults, rather than assigning the condition exclusively to the injector. It samples once per engine cycle and requires 41 failures among 82 samples, with Type A, one-trip reporting.

Check whether the measurement was eligible

Battery voltage must exceed 11 V, the ignition must be on and an injection pulse must be requested. Related injector-circuit, controller, boost-voltage and pull-in fault states inhibit this check, and the hardware must not report a dropped pulse.

Those prerequisites change the next diagnostic step: first establish that a real, valid injection event was evaluated, then identify whether its decay crossed the upper or lower limit. An absent test result while another injector electrical fault is active is inconclusive. Verification requires normal decay during eligible events using the vehicle's approved diagnostic method, not merely a cleared code or an assumed replacement injector.

Source and applicability

2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 1173.