OBD2 code P0406: EGR Sensor A Circuit High
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx.
Detected Root Component
EGR Valve
Technical Component Diagrams
EGR Valve Layout
Diag Expert technical diagram
EGR Valve Connector
Diag Expert technical diagram
Observed Symptoms
- Check engine light on
- EGR switched off
- Diesel: possibly reduced power
- Otherwise hardly noticeable
Possible Causes
- Sensor groundd or return wire open
- Signal wire shorted to 5 V or positive
- Sensor in the EGR valve faulty
- Moisture or corrosion in the connector
Tools Required
Interactive Diagnostic
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Parts likely to be the cause (Vanne EGR)
Vanne EGR
Photo d'illustration : Vanne EGR
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Frequently asked questions about code P0406
What does code P0406 mean? ▾
OBD2 code P0406: EGR Sensor A Circuit High. Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx.
What are the symptoms of code P0406? ▾
Code P0406 may cause: Check engine light on, EGR switched off, Diesel: possibly reduced power, Otherwise hardly noticeable. The intensity of these symptoms varies depending on the vehicle and driving conditions.
What causes code P0406? ▾
The most common causes of code P0406 are: Sensor ground or return wire open, Signal wire shorted to 5 V or positive, Sensor in the EGR valve faulty, Moisture or corrosion in the connector. A proper OBD2 diagnostic will pinpoint the exact cause.
Is it serious to drive with code P0406? ▾
Code P0406 has moderate severity (Warning). Short-term driving remains possible, but a prompt check is recommended to prevent worsening.
How do I fix code P0406? ▾
Start by reading the code with an OBD2 scanner, then follow the interactive decision tree on this page. Priority causes to check: Sensor ground or return wire open, Signal wire shorted to 5 V or positive, Sensor in the EGR valve faulty, Moisture or corrosion in the connector. Difficulty: Medium · Estimated time: 30-60min.