P0406 means the 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 wire, a sensor shorted to its 5V reference internally, or a sensor that has failed in the open position.
DTC/P0406·BMW
P0406 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)BMW
P0406 on a BMW means the 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 wire, a sensor shorted to its 5V reference internally, or a sensor that has failed in the open position.
Repair cost on BMW€98 - €938
What does P0406 mean on a BMW?
BMW 3 Series
2007–2024The N47 and B47 320d EGR sensor fails high (P0406) less often than low (P0405), but when it does it usually means the integrated sensor has failed internally rather than a wiring issue. The EGR connector is buried under the intake manifold support, requiring partial disassembly for inspection. ISTA or Carly adaptation reset is mandatory after valve replacement on the B47.
What causes P0406 on a BMW?
Beyond the generic causes listed on the main P0406 page, these are the BMW-specific patterns we see most often:
BMW 3 SeriesN47/B47 integrated sensor internal failure (open Hall element)
BMW 3 SeriesConnector buried under intake support, hard to inspect
How to diagnose P0406 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0406:
- Back-probe the sensor signal wire with the key on, engine off. Reading near 5V indicates an open signal or sensor failed open
- 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
- With the connector unplugged, the signal wire at the sensor side should read 0V (the sensor pulls it up when connected). At the ECU side it should still read 5V
- 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 BMW? (EUR)
Estimated repair costs on a BMW (BMW parts and labour typically run 40% 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 P0406 on BMW
These codes commonly cluster with P0406 on BMW vehicles:
FAQ: P0406 on BMW
What is the difference between P0405 and P0406?
P0405 means the signal is too low (below ~0.2V), usually a short to ground or failed sensor. P0406 means the signal is too high (above ~4.5V), usually an open wire, missing ground, or sensor failed open. Diagnostic steps are similar but the failure modes are opposite.
Can I drive with P0406?
Yes, short distances. The ECU disables EGR control, so the engine runs without EGR. Expect rough idle and possible limp mode on diesels. Long-term driving accelerates intake carbon buildup, especially on direct-injection engines. Plan the repair within a few weeks.
Is EGR delete a legal workaround for P0406?
No. EGR delete is illegal across the EU and UK, raises NOx emissions above legal limits, and fails periodic technical inspection (TÜV, ITV, TA, SKP). It can also void insurance and prevent vehicle registration transfer. Always repair the sensor or valve properly.
Why does P0406 come back after I replaced the sensor?
Two common reasons. First, EGR adaptation values were not reset after the new valve was fitted (required on BMW, Mercedes, VAG). Second, the carbon buildup that caused the original sensor stress is still present and damages the new sensor within months. Always clean the intake passages alongside any valve replacement.
Looking for the full P0406 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0406 guideSkanyx · BMW
Diagnosing P0406 on your BMW?
Connect any Bluetooth OBD2 adapter, scan for codes, and get AI-powered diagnostics with severity ratings and repair cost estimates.
Download Skanyx