The engine control module has detected that the air flow measured by the intake air flow sensor is outside the expected operating range. This indicates a performance discrepancy between the measured air mass and the calculated requirement based on engine load and RPM.
Dust, oil, or debris on the sensor element can distort air flow readings.
Cracks or loose clamps in the intake ducting after the sensor allow unfiltered air to enter, bypassing the measurement.
A severely restricted air filter can prevent the sensor from reading the expected volume of air.
Internal electronic failure of the sensor prevents it from providing accurate flow data.
Frayed or corroded wiring to the sensor can cause intermittent signal degradation.
The engine control module is unable to process the sensor signal correctly.
Yes, a heavily clogged filter restricts air flow, which may cause the sensor readings to fall outside the performance parameters expected by the PCM.
No. P2391 is almost always caused by a sensor fault, a dirty sensor, or a mechanical air leak. PCM failure is extremely rare for this specific code.
If the sensor is contaminated with oil or dust, cleaning it often restores the signal accuracy and clears the code.