P0405 means the EGR position sensor 'A' (the primary feedback sensor on the EGR valve) is sending a voltage below the normal operating range, typically below 0.2V. This is almost always a wiring fault, a corroded connector, or a sensor that has failed shorted to ground.
P0405 means the EGR position sensor 'A' (the primary feedback sensor on the EGR valve) is sending a voltage below the normal operating range, typically below 0.2V. This is almost always a wiring fault, a corroded connector, or a sensor that has failed shorted to ground.
P0405 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0405 and illuminates the check engine light.
If your vehicle has triggered P0405, you may notice one or more of these symptoms:
Here are the most common causes of P0405, ranked by how likely they are to be the culprit:
Generally yes, for short-term driving. Driveable. P0405 means the EGR position sensor (sensor A) is reporting a voltage lower than the expected operating range. The ECU loses confidence in EGR position feedback and may disable the EGR system or enter limp mode. Expect rough idle and a failed emissions test.
Follow these steps to pinpoint the root cause of P0405:
Repair costs for P0405 vary depending on the root cause and your vehicle. Here are typical estimates:
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0405 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:
These codes are often seen alongside P0405 or indicate related issues:
Short distances yes. The ECU disables EGR control when the position sensor signal is unreliable, so the engine runs without EGR (more NOx, more pinging on petrol, possible limp mode on diesel). Resolve within a couple of weeks to avoid intake carbon buildup and emissions test failure.
About 60% of the time it is the integrated sensor failing inside the EGR valve. The other 40% is wiring or connector corrosion. Always inspect the connector and measure the 5V reference at the sensor before condemning the valve, since wiring repairs are far cheaper.
On older vehicles with separate DPFE sensors (older Fords, some Japanese makes), yes. On modern BMW, Mercedes, and VAG vehicles the sensor is integrated into the EGR valve and not available separately. You replace the whole valve assembly.
Diesel EGR valves run hot and dirty. The position sensor sits directly on the valve, so it sees constant thermal cycling and soot. Hall-effect sensors degrade over time, and the connector seals fail. Failure between 100,000–150,000 km is typical on BMW N47/B47 and VW EA189/EA288.
Clean a carboned diesel EGR valve yourself for €10-30. Symptoms, step-by-step removal, when to clean vs replace, and how to verify the fix with OBD2.
EGR deletion is the hardest of the three diesel emissions cheats to detect with OBD2. Here is what the scan tool reveals, what it cannot, and three physical checks that close the gap.
Connect any Bluetooth OBD2 adapter, scan for codes, and get AI-powered diagnostics with severity ratings and repair cost estimates.
Download Skanyx