The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0403.
DTC/P0403·Mercedes-Benz
P0403 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0403 on a Mercedes-Benz means the ECU has detected a fault in the circuit that controls the EGR valve: it expected a specific voltage or current response and did not see it. The valve's own solenoid or motor is part of that circuit, so the cause is usually the valve itself, its connector or its wiring, and on electric valves, carbon that jams the valve can load the motor enough to trip the circuit monitor.
Typical repair cost, all makes€68 - €670
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Mercedes Sprinter
2010-2024OM651 Sprinters develop P0403 when the EGR solenoid winding fails from continuous duty cycles in commercial use. The EGR connector is exposed to road salt and water during winter operation, and corroded pins are a regular finding. Replacement valves should be ordered with a fresh connector pigtail and heat-shrink sealed.
What causes P0403 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0403 page, these are the patterns noted for Mercedes-Benz models:
Mercedes SprinterOM651 solenoid winding failure from continuous commercial duty
Mercedes SprinterConnector pin corrosion from road salt and water intrusion
How to diagnose P0403 on a Mercedes-Benz with OBD2
Follow these steps to pinpoint the root cause of P0403:
- Inspect the EGR valve connector for corrosion, bent pins, and water intrusion
- Unplug the connector and measure resistance across the solenoid terminals. Compare against the workshop manual spec (typically 5-15 ohms for solenoids, 2-10 ohms for motors)
- Back-probe the connector and verify the ECU is supplying voltage and ground in the correct sequence when the EGR is commanded
- Inspect the harness between the ECU and EGR valve for chafing, especially where it routes near hot exhaust components
- If the solenoid and wiring test good, remove the valve and check whether carbon is mechanically binding the pintle
How much does P0403 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0403 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 P0403
These codes are often seen alongside P0403 or point to related issues, on any make:
Looking for the full P0403 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0403 guideSkanyx · Mercedes-Benz
Diagnose P0403 on your Mercedes-Benz
Your car logged P0403. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the €68-€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.
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