The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0151.
DTC/P0151·Mercedes-Benz
P0151 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0151 on a Mercedes-Benz means the upstream oxygen sensor on bank 2 has reported a low voltage for too long, which reads as too much oxygen in the exhaust, a lean mixture. Bank 2 is the half of a V6, V8 or flat-six engine that does not contain cylinder 1 (a few inline-sixes with a split exhaust, such as BMW's M54, also have one). It is the same fault as P0131 on the other bank. The cause is either a real lean condition on that bank, such as a vacuum or exhaust leak, or a sensor or wiring fault that makes the signal read low.
Typical repair cost, all makes€45 - €320
Connect any standard Bluetooth OBD2 adapter to your Mercedes-Benz and Skanyx tells you what P0151 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
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Mercedes-Benz C-Class (V6)
2005-2011On Mercedes V6 and V8 engines, including the M272 V6 in the C 230, C 280, C 300 and C 350, bank 1 is the right-hand side of the engine and bank 2 the left-hand side, viewed in the direction of travel, whichever side the steering wheel is on. Each bank has its own upstream sensor ahead of its catalytic converter. If P0151 appears with P0174, look for an air leak on the left-hand side of the engine before replacing the left-hand pre-cat sensor.
What causes P0151 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0151 page, these are the patterns noted for Mercedes-Benz models:
Mercedes-Benz C-Class (V6)Air leak on the left-hand (bank 2) side of the M272 V6
Mercedes-Benz C-Class (V6)Ageing left-hand pre-cat sensor reading low
How to diagnose P0151 on a Mercedes-Benz with OBD2
Follow these steps to pinpoint the root cause of P0151:
- Read all stored codes and freeze frame data. P0174 alongside P0151 points to a real lean condition on bank 2. P0171 and P0174 together point to something both banks share, such as the MAF sensor, fuel pressure or a large intake leak
- Warm the engine and compare Bank 2 Sensor 1 with Bank 1 Sensor 1 on live data. A narrowband sensor stuck below about 0.2 volts while the bank 1 sensor keeps switching points at bank 2
- Check short- and long-term fuel trims for each bank. High positive trims on bank 2 only mean the engine computer is adding fuel to that bank, which supports a real lean condition rather than a sensor fault
- Smoke-test the intake. Look for leaks at the intake manifold gaskets, vacuum hoses and crankcase breather on the bank 2 side
- Inspect the exhaust between the bank 2 cylinder head and the sensor for leaks, cracks or a loose flange
- Inspect the bank 2 sensor wiring and connector for chafing against the exhaust or body that could short the signal to ground
- If trims are normal and no leaks are found, replace the bank 2 upstream sensor, clear the code and confirm it stays off after a drive cycle
How much does P0151 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0151 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 P0151
These codes are often seen alongside P0151 or point to related issues, on any make:
Looking for the full P0151 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0151 guideSkanyx · Mercedes-Benz
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