What does code P0131 mean on a Mercedes-Benz and is it safe to drive?
P0131: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1). Here's what it means on your Mercedes-Benz, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
What this code means
The upstream oxygen sensor on Bank 1 is reporting a voltage signal below the expected range. This can indicate a faulty sensor, a lean condition, or an exhaust leak near the sensor.
Common causes for your Mercedes-Benz
- Failed upstream oxygen sensor
- Exhaust leak before the sensor
- Lean fuel condition (vacuum leak, weak fuel pressure)
- Damaged sensor wiring or ground
Symptoms
- Check Engine Light
- Poor fuel economy
- Rough idle in some cases
- Failed emissions test
Typical fixes
- Replace upstream oxygen sensor (Bank 1, Sensor 1)
- Locate and fix exhaust leaks
- Smoke test for vacuum leaks
- Check fuel pressure
Repair cost range
For a Mercedes-Benz, repairs for P0131 often fall between $100 and $350, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Mercedes-Benz
Mercedes M272 P0131 upstream O2 sensor Bank 1 typically means a degraded sensor past 100k miles. Mercedes uses Bosch wideband sensors—use an OEM-quality replacement. Aftermarket sensors may not match the signal curve expected by the ECU and can cause continuous lean-related codes.
Most commonly affected models