Exhaust Gas Recirculation Circuit Range/Performance
Your EGR system isn't working as expected—it's either stuck open/closed or the sensor reading is out of range. Think of it like a valve that should let some exhaust back into the engine to reduce emissions, but it's not responding correctly.
The ECM monitors the EGR valve position sensor (potentiometer) feedback voltage, which should vary between 0.5V and 4.5V as the valve opens and closes. When actual valve movement doesn't match commanded position or sensor voltage stays outside expected range, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| EGR Valve Position Sensor Voltage | 0.5V–4.5V with proportional valve movement | Voltage stuck <0.5V or >4.5V, or no response to commands |
| EGR Flow Performance | Valve opens/closes within 2 seconds of command | No movement or excessive delay >2 seconds |
Code P0405 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0405 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.