P239DDiesel Intake Air Flow B Control System - Low Air Flow Detected
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P239D is the mirror image of P239C: the measured fresh-air mass remains below target although the control loop involving the B intake throttle is already at its limit. Candidates are an EGR valve that will not close and floods the intake with exhaust gas, a B flap stuck partly shut (often together with P2395), a restricted air filter or charge-air path, a turbocharger delivering too little, or an air-mass meter reading low. No manufacturer is known to publish P239D. Ford's 2023 diesels check the same condition for their one intake throttle as P02ED, with a detection time of ten seconds on the 6.7 L engine and half that on the 3.0 L. As the engine is short of air, black smoke, rapid soot loading of the DPF and a loss of power are typical; limp mode is possible.
- What you may notice
- Loss of power, possibly limp mode
- Black smoke
- Frequent particulate filter regenerations
- Likely causes
- LikelyEGR valve stuck open
- PossibleB throttle stuck partly closed
- PossibleClogged air filter or restricted charge-air path
- PossibleContaminated air-mass meter reading too low
- RareTurbocharger delivering too little boost
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €50 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.