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.
DTC/P0402·BMW
P0402 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)BMW
P0402 on a BMW 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.
Repair cost on BMW€95 - €1960
What does P0402 mean on a BMW?
BMW 3 Series
2007–2024The 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.
What causes P0402 on a BMW?
Beyond the generic causes listed on the main P0402 page, these are the BMW-specific patterns we see most often:
BMW 3 SeriesN47/B47 EGR valve seat carbon buildup preventing full closure
BMW 3 SeriesEGR cooler internal crack causing coolant intrusion and stuck-open valve
How to diagnose P0402 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0402:
- Read freeze frame data and check whether the fault appears at idle, cruise, or under load
- Remove the EGR valve and inspect the seat and pintle for carbon buildup preventing full closure
- Command the EGR valve closed with a scan tool and verify it seats fully (position sensor should read 0%)
- Inspect vacuum hoses (vacuum-operated systems) for leaks that hold the valve cracked open
- On diesel engines, inspect the EGR cooler for internal damage and verify the MAP sensor reads correctly against a known-good reference
How much does P0402 cost to fix on a BMW? (EUR)
Estimated repair costs on a BMW (BMW parts and labour typically run 40% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0402 on BMW
These codes commonly cluster with P0402 on BMW vehicles:
FAQ: P0402 on BMW
Can I drive with P0402?
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.
Is EGR delete legal in the EU?
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.
Will cleaning the EGR valve fix P0402?
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.
Why does my diesel keep throwing P0402 after cleaning?
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.
Looking for the full P0402 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0402 guideSkanyx · BMW
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