What it means
Same as P239C with the airflow below the threshold when the valve is commanded open - valve does not open fully or the path is restricted.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Diesel intake air flow valve B controls airflow through its part of the intake system. The control module checks measured airflow when it commands valve B open; this code sets when airflow is below the expected level, which can point to a valve that fails to open fully or a restricted passage.
Common causes
Most likely first.
- Valve not opening fully
- Restricted intake passage
- Carbon buildup, linkage, or actuator fault
Symptoms
- Check-engine light on
- Reduced engine power or sluggish acceleration
- Rough idle
How to diagnose it
- Review freeze-frame data and live airflow and valve-position readings to confirm airflow is low when valve B is commanded open.
- Inspect the intake passage serving valve B for restrictions, collapsed sections, or carbon buildup.
- Command valve B through its range with a scan tool and check whether the valve and linkage reach the open position.
- Inspect the B actuator and position-sensor wiring and connectors for damage, corrosion, or poor contact.
- If the passage is clear and movement is free, compare airflow and position readings with the manufacturer's specification to identify a sensor or actuator fault.
Common fixes
- Remove an obstruction or clean carbon from the intake passage serving valve B, where serviceable.
- Free or repair a sticking linkage that prevents valve B from opening fully.
- Repair damaged wiring or poor connections at the B actuator or position sensor.
- Replace the faulty B actuator, position sensor, or valve assembly confirmed by testing.
Can I keep driving?
A short drive may be possible if the engine remains stable, but avoid towing, steep climbs, and hard acceleration if power is reduced. Restricted airflow or a valve that cannot open can worsen sluggishness and rough running.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.