The Quick Answer above is the generic definition. What follows is what is documented for the BMW models that log P0431, checked against manufacturer data and owner reports.
DTC/P0431·BMW
P0431 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)BMW
P0431 on a BMW 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, which only exists on V6, V8, V10, V12, and some flat engine layouts.
Repair cost on BMW€125 - €1720
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BMW 3 Series
2007-2013P0431 on the 3 Series specifically applies to V8 variants such as the E90 and E92 M3 (S65 V8). The S65 has manifold-integrated pre-cats per bank, and Bank 2 (passenger side on RHD, driver side on LHD configuration depends on market) commonly fails first because of throttle body proximity heat soak. Replacement of the Bank 2 manifold-and-cat assembly is a five to seven hour shop job.
What causes P0431 on a BMW?
Beyond the generic causes listed on the main P0431 page, these are the documented BMW-specific patterns:
BMW 3 SeriesS65 V8 Bank 2 manifold-integrated pre-cat failure typical at 120,000 km
BMW 3 SeriesHeat soak from individual throttle bodies accelerating Bank 2 substrate wear
How to diagnose P0431 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0431:
- 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 BMW? (EUR)
Estimated repair costs for P0431 in EUR, compiled across makes. Expect BMW parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0431 on BMW
These codes commonly cluster with P0431 on BMW vehicles:
Looking for the full P0431 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0431 guideSkanyx · BMW
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