The Quick Answer above is the generic definition. What follows is the model-specific detail for the Audi models that log P0402.
DTC/P0402·Audi
P0402 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Audi
P0402 on a Audi 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.
Typical repair cost, all makes€68 - €1400
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Audi A4
2008-2024The 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 labour costs higher.
What causes P0402 on a Audi?
Beyond the generic causes listed on the main P0402 page, these are the patterns noted for Audi models:
Audi A4EA189/EA288 carbon buildup with tighter engine bay access on B8/B9
Audi A4EGR valve that cannot close fully after heavy carbon build-up at the seat
How to diagnose P0402 on a Audi 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 manufacturer-level software (a generic OBD2 reader cannot run this test) 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 Audi? (EUR)
Estimated repair costs for P0402 in EUR, compiled across makes. Expect Audi 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 P0402
These codes are often seen alongside P0402 or point to related issues, on any make:
Looking for the full P0402 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0402 guideSkanyx · Audi
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Your car logged P0402. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the €68-€1400 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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