P0406
Exhaust Gas Recirculation Sensor "A" Circuit High
Exhaust Gas Recirculation Sensor "A" Circuit High: the signal voltage is above the expected range. Without valid EGR feedback the ECU disables exhaust gas recirculation and may set further EGR codes.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Sensor circuit shorted to supplyCommon
- EGR position sensor failedPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- EGR Position Sensor
- EGR Sensor Wiring
P0406 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.