The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0157.
DTC/P0157·Mercedes-Benz
P0157 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0157 on a Mercedes-Benz 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
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Mercedes-Benz E-Class
2005-2011On the M272 V6 the bank 2 downstream sensor is on the left-hand exhaust, viewed in the direction of travel. Check that side's joints between the catalyst and the sensor for leaks before replacing the sensor, and use a direct-fit sensor matched to engine, bank and position.
What causes P0157 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0157 page, these are the patterns noted for Mercedes-Benz models:
Mercedes-Benz E-ClassExhaust leak on the left-hand pipe ahead of the downstream sensor
Mercedes-Benz E-ClassFailed bank 2 downstream sensor
How to diagnose P0157 on a Mercedes-Benz 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 Mercedes-Benz? (EUR)
Estimated repair costs for P0157 in EUR, compiled across makes. Expect Mercedes-Benz 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 · Mercedes-Benz
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