The Quick Answer above is the generic definition. What follows is the model-specific detail for the Audi models that log P0405.
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.
Typical repair cost, all makes€70 - €670
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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 patterns noted for Audi models:
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 for P0405 in EUR, compiled across makes. Expect Audi parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Codes related to P0405
These codes are often seen alongside P0405 or point to related issues, on any make:
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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