P239C
Diesel Intake Air Flow B Control System High Air Flow Detected
With diesel intake air flow valve B commanded closed the measured airflow is above the calibrated threshold - valve does not seat or position sensor offset.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Valve does not seat fullyCommon
Parts involved
- Diesel Intake Air Flow B
P239C is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.