What is the difference between P0403 and P0404?

P0403 is a pure electrical circuit fault (open, short, no response). P0404 means the circuit works, but the valve position does not match the commanded position. P0404 is almost always mechanical (carbon buildup, sticking pintle), while P0403 is usually electrical (solenoid, wiring, connector).

Can I drive with P0404?

Yes, short-term. Some modern diesels go into limp mode if the EGR cannot reach commanded positions, because the after-treatment calibration relies on EGR for NOx control. Plan the repair within a few weeks to avoid secondary DPF or SCR codes.

Will cleaning fix P0404 long-term?

On petrol engines, often yes if you also clean the intake manifold passages. On diesels with heavy soot output (BMW N47/B47, VAG EA189), cleaning may only last 20,000-40,000 km before the code returns. If the EGR cooler is degraded, replacement of the cooler-valve assembly is more durable.

Do I need to reset the EGR adaptation after replacing the valve?

Yes on most modern vehicles. BMW, Mercedes, and VAG all use stored adaptation values that must be reset and re-learned after a new EGR valve is fitted. INPA, VCDS, or a similar bi-directional scan tool is required. Skipping this step often causes the new valve to throw P0404 again within a few drive cycles.

P0404: Exhaust Gas Recirculation Control Circuit Range/Performance

Quick Answer

Safe to drive (short-term)

P0404 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.

Severity: Moderate · Emissions
Estimated repair cost: From €68 to €1400+, varies by vehicle

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What does P0404 mean?

P0404 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0404 and illuminates the check engine light.

Where it is on the car

Engine
Exhaust manifold
EGR cooler (diesels and many newer petrols)
EGR valve and position sensor
Intake manifold

What are the symptoms of P0404?

If your vehicle has triggered P0404, you may notice one or more of these symptoms:

Check engine light illuminated
Rough idle, especially after warm-up
Hesitation or stumble during light throttle
Slight loss of power and worse fuel economy
Failed emissions or periodic technical inspection

What causes P0404?

Here are the most common causes of P0404:

Carbon buildup restricting EGR valve pintle travel
: high
Faulty EGR position sensor reading inaccurate angle
: high
Worn or sticking valve mechanism unable to reach commanded position
: medium
Wiring or connector resistance affecting sensor signal
: medium
Software calibration issue after ECU reflash (rare)
: low

Is it safe to drive with P0404?

Generally yes, for short-term driving. Driveable. P0404 means the EGR valve is moving, but its actual position does not match what the ECU commanded. Expect rough idle and possible hesitation, and with the warning light on the fault can be recorded as a deficiency at a periodic inspection. Some diesels limit power to protect the DPF and SCR systems.

How do you diagnose P0404?

Follow these steps to pinpoint the root cause of P0404:

With manufacturer-level software (a generic OBD2 reader cannot run this actuator test), 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?

Repair costs for P0404 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Clean EGR valve and recalibrate (where supported)	€8–€25	€60–€180	€68–€205	Moderate
Replace EGR valve (electronic with integrated position sensor)	€150–€450	€80–€220	€230–€670	Moderate
Replace EGR cooler assembly (diesel, when valve is integrated)	€300–€800	€250–€600	€550–€1400	Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Full repair guides

EGR Valve Replacement Cost

Engines known for this code

P0404 on specific vehicles

P0404 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

P0404 on BMW

BMW 3 Series

See BMW-specific causes & cost

P0404 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost

P0404 on Audi

Audi A4

See Audi-specific causes & cost

P0404 on Mercedes-Benz

Mercedes Sprinter

See Mercedes-Benz-specific causes & cost

These codes are often seen alongside P0404 or indicate related issues:

Common questions about P0404

What is the difference between P0403 and P0404?: P0403 is a pure electrical circuit fault (open, short, no response). P0404 means the circuit works, but the valve position does not match the commanded position. P0404 is almost always mechanical (carbon buildup, sticking pintle), while P0403 is usually electrical (solenoid, wiring, connector).
Can I drive with P0404?: Yes, short-term. Some modern diesels go into limp mode if the EGR cannot reach commanded positions, because the after-treatment calibration relies on EGR for NOx control. Plan the repair within a few weeks to avoid secondary DPF or SCR codes.
Will cleaning fix P0404 long-term?: On petrol engines, often yes if you also clean the intake manifold passages. On diesels with heavy soot output (BMW N47/B47, VAG EA189), cleaning may only last 20,000-40,000 km before the code returns. If the EGR cooler is degraded, replacement of the cooler-valve assembly is more durable.
Do I need to reset the EGR adaptation after replacing the valve?: Yes on most modern vehicles. BMW, Mercedes, and VAG all use stored adaptation values that must be reset and re-learned after a new EGR valve is fitted. INPA, VCDS, or a similar bi-directional scan tool is required. Skipping this step often causes the new valve to throw P0404 again within a few drive cycles.

Read our detailed guides

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