How to Fix A Low Voltage O2 Sensor

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The oxygen sensor is one of the most important parts of an engine. Keeping it in good working order ensures that your car runs smoothly. 

If you are experiencing any issues with your O2 Sensor, don't panic! You can do many things to fix this problem, and we will go over some here.

What Does P0131 Mean?

O2 Sensor Circuit Low Voltage Bank 1 Sensor 1 is the description for error number P0131. This implies that the wiring has an issue, such as corrosion, breakage, or separation.

If the O2 Sensor may not be working, there's a problem with the ECU's connection, or the power source doesn’t provide adequate voltage to the Sensor.

Oxygen levels in exhaust gases escaping the engine are monitored by O2 Sensor, located in the exhaust system. 

This determines fuel combustion efficiency and ensures that the engine maintains the optimum fuel/air ratio for a clean burn. This aids the ECU in determining whether the fuel mixture is rich (low oxygen) or lean (high oxygen) (more oxygen).

How to fix P0131?

Despite a couple of exceptions, there are just a few basic fixes for a P0131:

Use scan tool to identify P0131

An OBD2 scanner connected to a car ready to scan

First, use a scan tool to confirm that P0131 is present; for the Best OBD II Scanners of 2021, please check here

Sometimes a material fouls the O2 Sensor, causing it to provide erroneous data to the ECM. When the debris blows away, the sensor resumes regular operation.

O2 Sensor

Perform physical inspection on the bank 1 sensor 1 wiring 

Alt-text: This is an Oxygen Sensor that may be located near the exhaust manifold.

Perform a physical inspection on the 1 sensor 1 wiring. Check for possible replacement or fixing of any defective wiring or connectors

Mapping out the Location of the Sensors

Check the on the bank 1 sensor 1 wiring 

Check the voltage and resistance of bank 1 sensor 1 and, if necessary, repair the wire or connectors.

This is a side by side comparison of the old and new oxygen sensor

Replace O2 Sensor

If you've gone through all of the other troubleshooting steps and concluded the oxygen sensor bank 1 sensor 1 is bad, replace it with a new one.

How to Check the O2 Sensor

Before you can start fixing you should first check the O2 Sensor. Use an OBD II scanner to examine the O2 Sensor and ascertain the fault code. If the P0131 code appears on the scanner, the number one oxygen sensor on Bank 1 is defective. Make sure to check for the following:

  1. Vacuum Lines- Check for leaks, cracks, and unplugged hoses in all vacuum lines.
  2. Fouling- Check for fouling from fuel additives or oil from worn engines in the oxygen sensor.
  3. Exhaust Leaks- Visually inspect the exhaust system from the exhaust manifold gasket to the tailpipe for any holes. 
  4. Electrical Connections Visually inspect the electrical connections between the ECU and the O2 Sensor. You can also use a Volt Ohm meter to verify for correct oxygen sensor operation.


  • The vehicle performs inefficiently.
  • Low-voltage power
  • Incorrect fuel/air combination
  • Idleness
  • Missing at a steady velocity
  • Starting is difficult.
  • Fuel economy suffering


  • The O2 Sensor may be defective.
  • The voltage can likely be insufficient
  • The oxygen sensor's connection may be broken.
  • It's possible that a wire or wires broke.
  • The wire's insulation may have deteriorated and rusted.
  • In the wire, there could be a short to ground.

Common Mistakes in Diagnosing

  • The most typical blunder is failing to establish an oxygen sensor circuit defect by clearing the code and test drive.
  • Another widespread misunderstanding is that an oxygen sensor failure can cause engine misfires or that engine misfires can cause the oxygen sensors in the car to read incorrectly.
  • A defective coolant temperature sensor might also lead to misdiagnosis.

How serious is the P0131?

A P0131 code can signal a significant problem with the car, causing it to operate poorly or even die while driving. When this code is present, it should be treated with caution and fixed as soon as possible.

P0131 Repair Cost

Many sensors cost between $20 and $100. Labor expenses vary depending on several factors, including how difficult it is to access your sensors. Labor charges for a sensor replacement are typically around $150.


What is the ideal voltage for an oxygen sensor?

The voltage of an O2 Sensor will cycle from 0.10 to 0.90 volts or about 1 volt. An O2 sensor must meet the 0.8x Volts amplitude criterion when in full operation. While in full operation, an O2 sensor must also exceed the 0.1x Volts amplitude criterion.

What is the location of the oxygen sensor bank 1?

Sensor 1 is always the oxygen sensor or Air/Fuel sensor in the exhaust manifold closest to the engine. Sensor 2 will be the O2 Sensor in or behind the catalytic converter. 

Sensor 1 will always be on the SAME side as the Number ONE cylinder in the engine's firing order on V6 and V8 engines.

How do I determine if I need an oxygen sensor upstream or downstream?

The upstream oxygen sensor is placed before the catalytic converter, whereas the downstream oxygen sensor is placed afterward. 

It's critical to pinpoint the location of the faulty oxygen sensor. The number and place of oxygen sensors are unique to each year, make, and vehicle model.

When an oxygen sensor fails, what does an automobile do?

When your car idles, it may run erratically or sound rough if it has a defective oxygen sensor. A defective oxygen sensor can affect your engine's timing, combustion intervals, and other vital aspects. You can notice stalling or poor acceleration as well.


It's not a good idea to muck about with a defective O2 Sensor. Whether you can fix it yourself or need to take it to a shop, take care of it as soon as possible. 

You don't want to stall in a busy intersection and cause an accident, or worse, end up stuck in a parking lot or on the side of the road.

It is essential to diagnose and repair your car as soon as possible to maintain it in excellent working order.

Do you experience low voltage O2 Sensor issues? How did you come up with a solution to the problem? Please let us know in the comments section below!