The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0404.
DTC/P0404·Mercedes-Benz
P0404 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0404 on a Mercedes-Benz means the EGR valve is responding to ECU commands, but not within the expected position range. The ECU asks for a specific opening (say 30%) and the position sensor reports something different. Carbon buildup restricting valve travel is by far the most common cause.
Typical repair cost, all makes€68 - €1400
Connect any standard Bluetooth OBD2 adapter to your Mercedes-Benz and Skanyx tells you what P0404 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 P0404 mean on a Mercedes-Benz?
Mercedes Sprinter
2010-2024OM651 Sprinters often see P0404 alongside P0401 due to heavy commercial duty cycles. The position sensor on the OM651 EGR valve is integrated and not serviceable separately. When the sensor drifts or the pintle sticks, replacement of the complete valve is required, plus Star Diagnosis or XENTRY for the adaptation reset. Skipping the adaptation will cause the code to return.
What causes P0404 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0404 page, these are the patterns noted for Mercedes-Benz models:
Mercedes SprinterOM651 integrated position sensor drift, full valve replacement required
Mercedes SprinterMandatory XENTRY adaptation after valve service or code returns
How to diagnose P0404 on a Mercedes-Benz with OBD2
Follow these steps to pinpoint the root cause of P0404:
- Use a scan tool to command the EGR valve through 0%, 25%, 50%, 75%, 100% and watch the position sensor feedback for delay or sticking
- Remove the valve and check for carbon buildup at the pintle and seat that limits travel
- Inspect the position sensor wiring and connector for corrosion or chafing
- Measure position sensor voltage at full closed and full open against the workshop spec
- After cleaning or replacement, perform the EGR adaptation procedure if the vehicle requires one (common on BMW, Mercedes, VAG)
How much does P0404 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0404 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 P0404
These codes are often seen alongside P0404 or point to related issues, on any make:
Looking for the full P0404 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0404 guideSkanyx · Mercedes-Benz
Diagnose P0404 on your Mercedes-Benz
Your car logged P0404. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the €68-€1400 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