Powertrain
generic / SAE
P0408
Exhaust Gas Recirculation Sensor "B" Circuit Low
The EGR position sensor A signal voltage is below the lower diagnostic threshold — open circuit, short to ground, or sensor fault. With no valid feedback, the ECU disables EGR and may set additional EGR codes.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number4 / 08
Possible causes
- EGR position sensor B failed high
- Wiring or connector fault medium
- Connector pins corroded - high contact resistance low
Inspection / repair
- Difficulty: medium
- DIY: possible
- Estimated cost: 60–400 €
- Estimated time: 0.3–2 h
- Component: egr position sensor
- Component: egr sensor wiring
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012