P0431 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Safe to drive (short-term)
P0431 on a Audi means the warm-up catalyst (the small pre-cat closest to the exhaust manifold) on Bank 2 is not heating up fast enough or converting cold-start emissions efficiently. Bank 2 is the cylinder bank that does not contain cylinder 1. It exists on V6, V8, V10, V12 and flat engines, and on some inline-sixes, such as BMW's N52 and N54, that split their exhaust into two halves and report cylinders 4 to 6 as Bank 2.
- Severity
- Moderate · Emissions
- Typical repair cost, all makes
- €125-€1720
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Audi and Skanyx tells you what P0431 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0431 mean on a Audi?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Audi models that log P0431.
Audi A6
2005-2024
On the Audi A6 3.0 TFSI (EA837 supercharged V6) and 3.0 TDI V6, P0431 points to the Bank 2 pre-cat, meaning the bank that does not contain cylinder 1. The EA837 is known for carbon buildup on intake valves, which causes uneven combustion and puts extra thermal load on the catalyst. Clean the intake valves before replacing a pre-cat, or the new one meets the same conditions.
What causes P0431 on a Audi?
Beyond the generic causes listed on the main P0431 page, these are the patterns noted for Audi models:
Ageing Bank 2 pre-cat with reduced oxygen storage on a high-mileage EA837
: Audi A6
Carbon-fouled intake valves causing uneven combustion on Bank 2
: Audi A6
How to diagnose P0431 on a Audi with OBD2
- Confirm the engine actually has two banks. If you see P0431 on an inline-4, suspect a scan tool error or a wiring fault
- Read freeze frame data and verify coolant temperature was below 40°C when the code set, which is typical of cold-start warm-up cat faults
- Scan for Bank 2 misfire codes (P0305 to P0308) and address those before condemning the pre-cat
- Graph Bank 2 upstream and downstream O2 sensors during cold start. The downstream sensor should stabilise near 0.45 V within 60 to 90 seconds on a healthy pre-cat
- Compare Bank 1 and Bank 2 downstream O2 sensor traces. If only Bank 2 is showing oscillation, the Bank 2 pre-cat is the likely culprit
How much does P0431 cost to fix on a Audi? (EUR)
Estimated repair costs for P0431 in EUR, compiled across makes. Expect Audi parts and labour towards the upper end of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace warm-up catalytic converter (Bank 2) | €280–€1400 | €120–€320 | €400–€1720 | Professional |
| Replace downstream O2 sensor (Bank 2) | €55–€170 | €70–€150 | €125–€320 | Moderate |
| Fix exhaust leak / replace manifold gasket (Bank 2) | €30–€130 | €100–€240 | €130–€370 | Moderate |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0431
These codes are often seen alongside P0431 or point to related issues, on any make:
Looking for the full P0431 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0431 guide