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.
DTC/P0405·Audi
P0405 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Audi
P0405 on a Audi 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.
Repair cost on Audi€88 - €838
What does P0405 mean on a Audi?
Audi A4
2008–2024B8 and B9 A4 2.0 TDI models share the EGR sensor failure modes with the Golf. The B8 has tighter packaging that makes the connector harder to access without removing the intake duct. On 3.0 TDI V6 (CCWA, CTBA), P0405 may indicate which bank with a suffix in the freeze frame data, but verify in VCDS first. Adaptation reset via VCDS or ODIS is required after valve replacement.
What causes P0405 on a Audi?
Beyond the generic causes listed on the main P0405 page, these are the Audi-specific patterns we see most often:
Audi A4EA189/EA288 sensor failure with restricted B8/B9 access
Audi A43.0 TDI V6 bank-specific fault requires freeze-frame review
How to diagnose P0405 on a Audi with OBD2
Follow these steps to pinpoint the root cause of P0405:
- Back-probe the sensor signal wire with the key on, engine off. A healthy sensor at rest should read 0.5–1.0V (varies by vehicle, check workshop spec)
- Verify 5V reference at the sensor connector. If reference is missing, trace the wire back toward the ECU
- Unplug the sensor connector and inspect for water intrusion, corrosion, and bent pins
- With the connector unplugged, the signal wire should read 5V at the ECU side. If it reads 0V, the wire is shorted to ground
- If wiring and reference are good, the sensor itself is the most likely failure. On most modern systems, replacing the integrated valve assembly is the practical fix
How much does P0405 cost to fix on a Audi? (EUR)
Estimated repair costs on a Audi (Audi parts and labour typically run 25% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0405 on Audi
These codes commonly cluster with P0405 on Audi vehicles:
FAQ: P0405 on Audi
Can I drive with P0405?
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.
Is P0405 the sensor or the wiring?
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.
Can I just replace the EGR sensor without the valve?
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.
Why is the EGR position sensor failing on my diesel?
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.
Looking for the full P0405 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0405 guideSkanyx · Audi
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