P0402 means the EGR system is flowing too much exhaust gas back into the intake manifold. The most common cause is an EGR valve stuck partially open, often due to carbon buildup on the valve seat. Diesel engines are especially vulnerable because of higher soot output.
P0402 means the EGR system is flowing too much exhaust gas back into the intake manifold. The most common cause is an EGR valve stuck partially open, often due to carbon buildup on the valve seat. Diesel engines are especially vulnerable because of higher soot output.
P0402 è un codice diagnostico di guasto relativo a emissioni, classificato con gravità moderate. Quando la centralina (ECU) del tuo veicolo rileva questa condizione, memorizza P0402 e accende la spia motore.
Se il tuo veicolo ha attivato P0402, potresti notare uno o più di questi sintomi:
Ecco le cause più comuni di P0402, ordinate in base alla probabilità che siano la causa del problema:
In genere sì, per brevi tragitti. Driveable short-term, but excessive EGR flow causes rough idle, hesitation, and may stall the engine at low RPM. Extended driving with excess EGR contaminates the intake and accelerates carbon buildup on intake valves (especially direct-injection engines). Get it fixed before next emissions test.
Segui questi passaggi per individuare la causa principale di P0402:
I costi di riparazione di P0402 variano a seconda della causa principale e del tuo veicolo. Ecco le stime tipiche:
Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.
P0402 si comporta in modo diverso a seconda del tuo veicolo. Seleziona la tua auto qui sotto per cause specifiche del modello, problemi noti e stime dei costi adeguate:
2007–2024
The 320d with N47 and later B47 engines is notorious for EGR-related faults. Carbon buildup at the EGR valve seat is virtually guaranteed past 120,000 km, and the EGR cooler often cracks internally, leaking coolant into the exhaust stream. When P0402 appears alongside P0401 or low-coolant warnings, suspect cooler failure. BMW issued recall campaigns in several EU markets for N47/B47 EGR cooler fires.
Costi stimati per i proprietari di BMW 3 Seriesadeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici BMW
Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.
2009–2024
Golf TDI models with the EA189 (pre-Dieselgate) and EA288 (post-fix) engines commonly throw P0402 after the emissions software update was applied. The remapped EGR strategy runs the valve at higher duty cycles, which accelerates carbon buildup at the seat. Cleaning the valve and intake manifold passages restores normal operation. On 1.4 TSI petrol Golfs, the integrated EGR cooler in the exhaust manifold can also stick open.
Costi stimati per i proprietari di Volkswagen Golfadeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici Volkswagen
Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.
2008–2024
The A4 2.0 TDI (B8 and B9 chassis) shares EA189 and EA288 engines with the Golf and suffers identical EGR carbon issues. The valve is harder to access on the A4 due to tighter engine bay packaging, which pushes labor costs higher. On 3.0 TDI V6 models, the dual EGR coolers add complexity and parts cost when failure occurs.
Costi stimati per i proprietari di Audi A4adeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici Audi
Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.
2010–2024
Sprinter vans with the OM651 2.1 CDI engine are heavy commercial users that see EGR faults early due to high duty cycles and frequent low-load city driving. The EGR cooler interacts with the AdBlue (SCR) system, so a stuck-open EGR valve often pulls down NOx sensor readings and triggers AdBlue limp-mode countdown. Cleaning is rarely a long-term fix on commercial Sprinters, replacement is more common.
Costi stimati per i proprietari di Mercedes Sprinteradeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici Mercedes-Benz
Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.
Questi codici compaiono spesso insieme a P0402 o indicano problemi correlati:
Short distances yes, but expect rough idle and possible stalling. Excessive EGR flow dumps soot and exhaust into the intake, which accelerates carbon buildup on intake valves, especially on direct-injection engines. Get it diagnosed within a few weeks.
No. EGR delete is illegal across the EU and UK. It increases NOx emissions, triggers a permanent check engine light, fails the periodic technical inspection (TÜV in Germany, ITV in Spain, TA in Lithuania, SKP in Poland), and can result in vehicle deregistration. Stick to cleaning or replacement.
Often yes. P0402 is usually caused by carbon stopping the valve from closing fully. Removing the valve, soaking it in EGR cleaner or carb cleaner, and clearing the seat resolves the code on roughly half of cases. If the solenoid or motor itself has failed, replacement is needed.
Diesel engines produce far more soot than petrol, so the EGR valve re-fouls quickly. If the EGR cooler is also blocked or leaking internally, the valve will stick open again within months. On heavily affected engines (BMW N47, M57), the cooler often needs replacement alongside the valve.
An EGR valve clean runs 80 to 200 euros, a full replacement 150 to 600. Here is what each costs on a 1.6 and 2.0 TDI, and when carbon means clean over replace.
Clean a carboned diesel EGR valve yourself for €10-30. Symptoms, step-by-step removal, when to clean vs replace, and how to verify the fix with OBD2.
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