The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0405.
DTC/P0405·Mercedes-Benz
P0405 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0405 on a Mercedes-Benz 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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Mercedes Sprinter
2010-2024OM651 Sprinter EGR position sensors fail regularly under heavy commercial use, often before 120,000 km. The Mercedes connector is exposed and prone to road salt corrosion in northern European winters. P0405 frequently appears alongside P0401 or P0404, and Star Diagnosis (XENTRY) is needed for proper adaptation reset after replacement. Aftermarket EGR valves with integrated sensors are available, but quality varies.
What causes P0405 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0405 page, these are the patterns noted for Mercedes-Benz models:
Mercedes SprinterOM651 Hall-effect sensor failure from heavy commercial duty cycles
Mercedes SprinterRoad salt corrosion at exposed connector in winter operation
How to diagnose P0405 on a Mercedes-Benz 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 Mercedes-Benz? (EUR)
Estimated repair costs for P0405 in EUR, compiled across makes. Expect Mercedes-Benz 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 · Mercedes-Benz
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