P0405Powertrain
Powertrain · SAE
EGR Position Sensor A Circuit Low
Meaning
The feedback voltage from EGR position sensor A is below the minimum calibrated threshold, typically under 0.2 V, indicating a short to ground or sensor failure.
Common causes
- Short to ground in sensor signal wire
- Corroded or damaged connector pin
- Failed position sensor with internal short
Symptoms
- MIL illuminated
- EGR valve stuck or commands ignored by ECU
- Possible detonation
Severity
Moderate — EGR control is compromised, resulting in increased NOx emissions.
What to do
- Backprobe sensor signal pin and measure voltage (expected range 0.5–4.5 V)
- Check signal wire for short to ground
- Inspect connector and sensor body
- Replace sensor if wiring is intact