Parts
$30–120
P0405 — EGR Sensor A Circuit Low
SAFEIs it safe to drive? EGR position sensor is reporting a low voltage signal — emissions fault, not a safety issue; drivable.
What P0405 means
The EGR position sensor (or differential pressure sensor on some designs) is sending a voltage below the expected minimum range. The ECM either sees a wiring short to ground or a failed sensor element.
Most likely causes (in order)
- Position sensor wiring shorted to ground
- Connector pin corroded or backed out
- EGR position sensor element failed internally
- EGR valve solenoid coil shorting into sensor circuit
- Water or coolant contamination in connector
Symptoms you might notice
- CEL on
- possible rough idle if EGR behavior is affected
- failed emissions test
What to check first
Backprobe the sensor signal wire with a multimeter at idle — should read roughly 0.5–1.5V with EGR closed, rising to 3–4.5V commanded open. A reading at 0V confirms a short to ground; unplug the sensor and see if voltage appears (confirms bad sensor vs. bad wiring).
Repair cost & difficulty
Labor
0.5–1.5 hr
Difficulty
DIY-friendly