The Quick Answer above is the generic definition. What follows is the model-specific detail for the Audi models that log P0406.
DTC/P0406·Audi
P0406 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Audi
P0406 on a Audi means EGR position sensor 'A' is sending a voltage above its normal operating range, typically above 4.5V. This is usually caused by an open signal or ground wire, a short to the 5V reference, or a sensor that has failed internally and drives its signal high.
Typical repair cost, all makes€70 - €670
Connect any standard Bluetooth OBD2 adapter to your Audi and Skanyx tells you what P0406 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0406 mean on a Audi?
Audi A4
2008-2024B8 and B9 A4 2.0 TDI suffer the same P0406 failure modes as the Golf, plus restricted access due to the larger intake manifold. An EGR adaptation with manufacturer-level software (VCDS or ODIS) is normally part of the job after sensor or valve service.
What causes P0406 on a Audi?
Beyond the generic causes listed on the main P0406 page, these are the patterns noted for Audi models:
Audi A4EA189/EA288 connector issues identical to Golf, with restricted A4 access
Audi A4Loose or damaged EGR connector after intake or turbo work
How to diagnose P0406 on a Audi with OBD2
Follow these steps to pinpoint the root cause of P0406:
- Back-probe the sensor signal wire at the sensor with the key on, engine off. A reading near 5V there with the valve closed points to the sensor or a short to the reference; a normal reading at the sensor but a high value in live data points to a break in the signal wire towards the ECU
- Verify the sensor ground at the connector. If ground is missing, the signal will float high
- Unplug the connector and check for damaged pins or unseated terminals
- Check the signal wire for continuity between the sensor connector and the ECU, and for a short to the 5V reference or battery voltage. Use the wiring diagram to see how the ECU treats an unplugged input, because whether it floats high or low depends on the ECU design
- If wiring and ground are good and the sensor reads 5V steadily, the integrated sensor has failed. Replace the EGR valve assembly
How much does P0406 cost to fix on a Audi? (EUR)
Estimated repair costs for P0406 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 P0406
These codes are often seen alongside P0406 or point to related issues, on any make:
Looking for the full P0406 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0406 guideSkanyx · Audi
Diagnose P0406 on your Audi
Your car logged P0406. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the €70-€670 repair range so you know the number before a shop quotes you. Free on iPhone and Android, and you do not need to be a mechanic to read it.
Get Skanyx free