Can I drive with P0405?

Short distances yes. The ECU disables EGR control when the position sensor signal is unreliable, so the engine runs without EGR (more NOx, more pinging on petrol, possible limp mode on diesel). Resolve within a couple of weeks to avoid intake carbon buildup and a deficiency at your next periodic inspection.

Is P0405 the sensor or the wiring?

More often it is the integrated sensor failing inside the EGR valve, but wiring or connector corrosion is a regular second finding. Always inspect the connector and measure the 5V reference at the sensor before condemning the valve, since wiring repairs are far cheaper.

Can I just replace the EGR sensor without the valve?

On older vehicles with separate DPFE sensors (older Fords, some Japanese makes), yes. On modern BMW, Mercedes, and VAG vehicles the sensor is integrated into the EGR valve and not available separately. You replace the whole valve assembly.

Why is the EGR position sensor failing on my diesel?

Diesel EGR valves run hot and dirty. The position sensor sits directly on the valve, so it sees constant thermal cycling and soot. Hall-effect sensors degrade over time, and the connector seals fail. Failure between 100,000-150,000 km is typical on BMW N47/B47 and VW EA189/EA288.

P0405: Exhaust Gas Recirculation Sensor "A" Circuit Low

Quick Answer

Safe to drive (short-term)

P0405 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.

Severity: Moderate · Emissions
Estimated repair cost: From €70 to €670+, varies by vehicle

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What does P0405 mean?

P0405 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0405 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 P0405?

If your vehicle has triggered P0405, you may notice one or more of these symptoms:

Check engine light illuminated
Rough or hunting idle
Reduced power, especially on diesels in limp mode
Hesitation during acceleration
Failed emissions or periodic technical inspection

What causes P0405?

Here are the most common causes of P0405:

EGR position sensor shorted to ground internally
: high
Damaged signal wire between sensor and ECU (chafed, grounded)
: high
Corroded or water-damaged sensor connector pulling signal low
: medium
Open 5V reference supply to the sensor
: medium
Failed ECU 5V reference circuit (rare, usually affects multiple sensors)
: low

Is it safe to drive with P0405?

Generally yes, for short-term driving. Driveable. P0405 means the EGR position sensor (sensor A) is reporting a voltage lower than the expected operating range. The ECU loses confidence in EGR position feedback and may disable the EGR system or enter limp mode. Expect rough idle, and with the warning light on the fault can be recorded as a deficiency at a periodic inspection.

How do you diagnose P0405?

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?

Repair costs for P0405 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Clean and repair EGR sensor connector	€10–€60	€60–€180	€70–€240	Moderate
Replace EGR valve (sensor integrated)	€150–€450	€80–€220	€230–€670	Moderate
Repair or replace EGR wiring harness section	€20–€120	€120–€350	€140–€470	Professional

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

Full repair guides

EGR Valve Replacement Cost

P0405 on specific vehicles

P0405 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

P0405 on BMW

BMW 3 Series

See BMW-specific causes & cost

P0405 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost

P0405 on Audi

Audi A4

See Audi-specific causes & cost

P0405 on Mercedes-Benz

Mercedes Sprinter

See Mercedes-Benz-specific causes & cost

These codes are often seen alongside P0405 or indicate related issues:

Common questions about P0405

Can I drive with P0405?: Short distances yes. The ECU disables EGR control when the position sensor signal is unreliable, so the engine runs without EGR (more NOx, more pinging on petrol, possible limp mode on diesel). Resolve within a couple of weeks to avoid intake carbon buildup and a deficiency at your next periodic inspection.
Is P0405 the sensor or the wiring?: More often it is the integrated sensor failing inside the EGR valve, but wiring or connector corrosion is a regular second finding. Always inspect the connector and measure the 5V reference at the sensor before condemning the valve, since wiring repairs are far cheaper.
Can I just replace the EGR sensor without the valve?: On older vehicles with separate DPFE sensors (older Fords, some Japanese makes), yes. On modern BMW, Mercedes, and VAG vehicles the sensor is integrated into the EGR valve and not available separately. You replace the whole valve assembly.
Why is the EGR position sensor failing on my diesel?: Diesel EGR valves run hot and dirty. The position sensor sits directly on the valve, so it sees constant thermal cycling and soot. Hall-effect sensors degrade over time, and the connector seals fail. Failure between 100,000-150,000 km is typical on BMW N47/B47 and VW EA189/EA288.

Read our detailed guides

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