P0409EGR Sensor A Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. EGR sensor A is usually the valve position sensor (on older Fords the DPFE pressure sensor). P0409 is its general circuit code, for a missing or implausible signal that the module does not classify as low or high. No manufacturer document available to us uses it – GM, Ford and Saab report sensor A as P0405/P0406, Ford intermittent faults as P046D – so the description follows CARB, which requires input circuits to be checked for continuity and range. EGR is usually switched off.
- What you may notice
- Check engine light on
- EGR switched off
- Otherwise usually unremarkable
- Likely causes
- LikelyConnector or wire of the position sensor open or loose
- PossibleEGR valve with integrated sensor faulty
- Rare5 V reference or ground disturbed
- RareEngine module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.