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P0131

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

The engine computer is seeing a very low signal from the front oxygen sensor on bank 1. This usually means the engine may be running too lean, or the sensor, wiring, or connector has a problem. It can cause rough running, higher fuel use, and emissions issues.

Severity3/5 Moderate
Can I drive?⚠ With caution

You may be able to drive short distances, but the engine can run poorly and fuel economy may suffer. Do not ignore it, because a lean condition can damage the engine or catalytic converter if the problem is severe.

DIY
$20–$250
Shop
$120–$600
Difficulty
intermediate

What It Means

P0131 indicates the powertrain control module has detected a persistently low voltage signal from the upstream oxygen sensor on Bank 1, Sensor 1. This sensor is used for fuel control, so a low reading can be caused by a true lean exhaust condition, an exhaust leak, vacuum leak, fuel delivery problem, or a faulty sensor/circuit. The code sets when the signal stays below the expected range for too long under the right operating conditions.

Symptoms

Common Causes

1. Vacuum leak or unmetered air entering the enginehigh
2. Faulty upstream oxygen sensor (Bank 1 Sensor 1)high
3. Exhaust leak before or near the front oxygen sensormedium
4. Wiring damage, corrosion, or loose connector at the oxygen sensormedium
5. Low fuel pressure, restricted fuel filter, or failing fuel pumpmedium
6. Mass air flow sensor or intake air measurement issuelow
7. Engine mechanical problem causing lean runninglow

Related Codes

FAQ

What does P0131 mean on a car?

It means the upstream oxygen sensor on Bank 1 is showing a voltage that is too low, or the engine is actually running too lean.

Can a bad oxygen sensor cause P0131?

Yes. A failing front oxygen sensor is a common cause, but vacuum leaks and fuel problems are also common.

Will P0131 make the car run poorly?

It can. The engine computer may not control fuel mixture correctly, which can cause rough idle, hesitation, and poor fuel economy.

Is P0131 the same as Bank 1 Sensor 1?

Yes. P0131 refers to the upstream oxygen sensor on Bank 1, also called Sensor 1.

Can I clear P0131 without fixing it?

You can clear it, but it will usually come back if the underlying problem is still there.