What it means
Diesel intake air flow valve B is mechanically stuck open - the ECU cannot close it for anti-shudder shutdown or EGR mixing assistance.
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 the intake, including airflow used for EGR mixing and engine shutdown behavior. This code sets when the module detects that valve B remains open when it should close, so the engine may receive more air than commanded.
Common causes
Most likely first.
- Valve stuck open due to soot or broken linkage
- Carbon or debris buildup preventing free movement
- Component wear with age - mechanical play
Symptoms
- Check-engine light on
- Reduced engine power or sluggish acceleration
- Rough idle or stalling
How to diagnose it
- Check freeze-frame data and live commanded and actual positions to confirm that valve B is being told to close but remains open.
- Inspect valve B and its linkage for soot, debris, a broken connection, or wear that could hold the valve open.
- With the engine off and following the manufacturer’s safety procedure, check whether the valve moves freely through its intended range.
- Use the scan tool to command valve B open and closed, if supported, and observe whether its position follows the command.
- If the valve moves freely but remains reported open, test the actuator and position feedback circuit against the manufacturer’s specification.
Common fixes
- Remove soot or debris that prevents valve B from closing, using the approved cleaning procedure.
- Repair or replace broken or worn valve B linkage.
- Replace a sticking or mechanically worn valve B assembly.
- Repair a confirmed actuator or position-feedback fault.
Can I keep driving?
Rough idle, stalling, or reduced power can make driving unpredictable, especially in traffic. Avoid demanding trips and stop if the engine stalls or loses the power needed to keep up safely.
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.