The Quick Answer above is the generic definition. What follows is the model-specific detail for the BMW models that log P0157.
DTC/P0157·BMW
P0157 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)BMW
P0157 on a BMW means the Bank 2 downstream oxygen sensor (after the catalytic converter, Sensor 2) is reporting a voltage that stays too low for too long. Bank 2 is the half of the engine without cylinder 1, found on most V6 and V8 engines, flat-six engines and a few straight sixes with a split exhaust. A low reading usually means outside air is reaching the sensor through an exhaust leak, the sensor has failed, or the bank 2 exhaust really is lean. A healthy downstream sensor reads a relatively steady 0.6-0.8V when the catalytic converter is working.
Typical repair cost, all makes€45 - €310
Connect any standard Bluetooth OBD2 adapter to your BMW and Skanyx tells you what P0157 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 P0157 mean on a BMW?
BMW 3 Series
2005-2013On the N52 and N54 straight sixes the bank 2 downstream sensor sits after the catalyst for cylinders 4-6 and reads exhaust from those three cylinders only. Check the exhaust joints between that catalyst and the sensor for leaks before replacing the sensor.
BMW 5 Series
2003-2010Bank 2 on the N62 V8 is cylinders 5-8, and BMW's N62 training material shows the catalysts built into the exhaust manifolds. A leak at the joints after that manifold lets outside air reach the downstream sensor and drags its voltage down, so check them before buying a sensor.
What causes P0157 on a BMW?
Beyond the generic causes listed on the main P0157 page, these are the patterns noted for BMW models:
BMW 3 SeriesExhaust leak between the cylinder 4-6 catalyst and the sensor
BMW 3 SeriesFailed post-catalyst sensor for cylinders 4-6
BMW 5 SeriesExhaust leak after the bank 2 manifold catalyst
BMW 5 SeriesFailed downstream sensor on cylinders 5-8
How to diagnose P0157 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0157:
- Confirm which sensor the code means before buying parts: Bank 2 is the cylinder bank that does not contain cylinder 1, and Sensor 2 is the one after the catalytic converter. Check the cylinder numbering for your engine in the service information, because the side of the car bank 2 sits on is not the same on every engine
- Read freeze frame data and check for companion codes (P0430, P0174, P0171) that suggest a converter problem or a lean condition
- Inspect the bank 2 exhaust between the catalytic converter and the downstream sensor for cracks, loose clamps or leaking gaskets. A ticking sound on a cold start often gives a leak away
- Inspect the Bank 2 Sensor 2 connector and wiring for corrosion, heat damage or chafing
- Use a scan tool to view the downstream sensor voltage. A healthy sensor reads around 0.6-0.8V steady. A reading stuck below 0.2V points to sensor failure or an exhaust leak
- Compare long-term fuel trim on bank 2 with bank 1. If bank 2 is adding a lot more fuel, that bank is genuinely lean and the sensor may simply be reporting it
- Substitute a known-good sensor, or swap the bank 1 and bank 2 downstream sensors if they use the same part number. If the low voltage follows the sensor (the code changes to P0137), the sensor is faulty
How much does P0157 cost to fix on a BMW? (EUR)
Estimated repair costs for P0157 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.
Codes related to P0157
These codes are often seen alongside P0157 or point to related issues, on any make:
Looking for the full P0157 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0157 guideSkanyx · BMW
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