What does code P0131 mean on a Mercury and is it safe to drive?
P0131: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1). Here's what it means on your Mercury, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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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 Mercury
- 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 Mercury, 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.