What does it mean?
This code says the A intake air flow control valve is not closing: it stays open regardless of what the module commands. The software recognises this either from position feedback that never falls, or from an air flow that remains at full open levels while a restriction was requested. On a diesel the consequences are specific. Without the ability to throttle the intake, the pressure difference needed to draw exhaust gas through the recirculation circuit is missing, so nitrogen oxide output rises, and the engine cannot be choked at shutdown, which is why it shakes when it stops. The regeneration strategy for the particulate filter also relies on this valve to raise exhaust temperature, so filter loading tends to get worse.
Symptoms
- The engine shudders noticeably when it is switched off, one of the most recognisable signs
- MIL on, usually with EGR flow insufficient codes alongside
- Rough idle when cold and slightly noisier combustion
- Particulate filter regeneration starting frequently or failing to complete
- Higher nitrogen oxide output and a failed emissions inspection
- Sometimes no obvious power loss, since a fully open intake does not restrict airflow
Likely causes
- Heavy carbon build-up holding the plate open in its bore, which is the classic finding on high mileage diesels
- Broken or disconnected linkage between the actuator and the plate
- Failed actuator motor or return spring, so nothing drives or holds the plate closed
- Internal position sensor reading incorrectly, so the module believes the valve is elsewhere
- Loss of vacuum supply on vacuum operated valves, from a split hose, a leaking diaphragm or a faulty control solenoid
- Open circuit in the actuator control wiring or a disconnected connector
- Valve installed incorrectly or not adapted after cleaning or replacement
How to fix it
- Compare commanded and actual valve position in live data, then command the valve closed with the actuator test and watch whether the reported position moves
- Remove the intake duct or the valve itself and check visually whether the plate moves and seals
- Clean carbon from the plate and bore if the valve is serviceable, and check that the plate is not scored or bent
- Inspect the linkage and return spring for breakage or disconnection
- On vacuum operated systems, apply vacuum directly with a hand pump and confirm the plate closes and holds
- Test the control and feedback circuits for open circuit and voltage drop, moving the harness during the test
- Fit a new actuator or valve assembly when the mechanism is proven faulty, carry out the required adaptation, then confirm a smooth shutdown and normal EGR flow