P0405EGR Sensor A Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- 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 with a 5 V supply; on Ford until about 2011 it was the DPFE differential pressure sensor. P0405 means its signal is below the lower limit – GM 2018 below 11 % of 5 V (MIL after two trips), Ford below 5 % of full scale for 4 s, Saab below 0.26 V. The cause is a short to ground or an open signal or 5 V wire. EGR position control is then switched off.
- What you may notice
- Check engine light on
- EGR switched off
- Diesel: possibly reduced power
- Otherwise hardly noticeable
- Likely causes
- LikelyWire or connector to the EGR valve open or shorted to ground
- PossiblePosition sensor in the EGR valve faulty (usually one unit with the valve)
- PossibleOlder Ford: DPFE sensor faulty
- RareShared 5 V reference shorted
- 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.