P0131 — O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
Category: Powertrain Severity: Medium
Updated:
DTC code P0131 means: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1). It falls under the "Powertrain" category, with an estimated severity of Medium. Common causes include faulty upstream O2 sensor, exhaust leak before the sensor and vacuum leak (lean mixture); it's worth confirming the diagnosis before replacing parts.
Possible causes
- Faulty upstream O2 sensor
- Exhaust leak before the sensor
- Vacuum leak (lean mixture)
- Signal wire shorted to ground
Symptoms
- Check engine light
- Higher fuel consumption
- Rough idle
- High emissions
How to diagnose it step by step
- Check for exhaust leaks near the manifold.
- Watch the sensor signal while running.
- Force a rich condition (snap throttle) and check voltage rises.
- Check the wiring.
- Replace the sensor if it doesn't respond.
How to fix it
Watch the O2 signal: it should switch between 0.1 and 0.9 V. If it stays low even under hard acceleration, replace the sensor; if it responds, look for exhaust or vacuum leaks.
Estimated repair cost
Upstream O2 sensor installed: $100–300.
Frequently asked questions
What does DTC code P0131 mean?
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1).
Is code P0131 serious?
Severity Medium. Not urgent, but worth diagnosing to avoid bigger damage.
Can I keep driving with code P0131?
Yes, you can drive; fix it to avoid long-term catalytic converter damage.
Related codes
P0130 P0132 P0133 P0134 P0135 P0136 P0137 P0138 P0139 P0128
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