Diagnostic Trouble Code P0131

P0131 “O2 Sensor Circuit Low Voltage Bank 1 Sensor 1”


What is code P0131?

Code P0131 stands for “O2 Sensor Circuit Low Voltage Bank 1 Sensor 1”. This diagnostic trouble code can show up for reasons related to one of the oxygen sensors in your vehicle that helps to regulate the air and fuel that enter the engine. Therefore, it is important to have a qualified technician diagnose the specific problem that caused the code to be stored in your vehicle’s computer.

Get this checked out soon by a CarAdvise shop, where the work will be guaranteed, and one of our expert techs will review any repair orders.

What does code P0131 mean?

If code P0131 shows up on a diagnostic scan of your vehicle, the information indicates to a technician that there is something wrong with either an oxygen sensor (also called an O2 sensor) in bank 1, or an improper air to fuel ratio entering your engine. The ECM (Engine Control Module) has detected the problem and turned on the check engine light.

Your engine requires that a specific mixture of air and fuel enter the combustion chambers in order for combustion to happen as it should. When that air/fuel ratio is out of balance – whether there is too much fuel (running “rich”) or too little fuel (running “lean”) – your engine will not run as it should. Harmful emissions increase, fuel economy drops, and a number of problems can affect drivability. Engine damage can also occur in some cases.

To help maintain a suitable air/fuel mixture, your vehicle is fitted with special sensors. They are mounted in the exhaust system and measure the percentage of oxygen present in the exhaust gases. Data from these oxygen sensors is sent to the ECM where it is analyzed and used to adjust the air/fuel ratio accordingly. Bank 1 refers to the side of a “V” style engine (V6, V8, etc.) that contains cylinder number 1 (many engines have only one bank). Sensor 1 refers to the oxygen sensor placed upstream of the catalytic converter, the one that measures oxygen in the exhaust gases coming directly from the engine.

If the ECM detects low voltage coming from this sensor – or if it identifies a prolonged lean operating condition – it can store code P0131 and turn on the check engine light.


What causes code P0131?

A number of causes can trigger a code P0131. That is why an accurate diagnosis is essential. Causes of this code include:

Most likely

  • Faulty oxygen sensor ($200-$500)
  • Damaged or deteriorated wiring to the oxygen sensor
  • Low fuel pressure

Other possibilities


What symptoms are associated with this code?

Common signs associated with a code P0131 include the following:

  • The check engine light is on or flashing
  • Rough idle or misfire
  • Engine stalling
  • Reduced fuel economy


How does a technician diagnose code P0131?

If a diagnostic scan of your vehicle indicates a code P0130, a technician will perform tests to pinpoint the problem. These tests include checking for any related trouble codes. The technician will also use the scan tool to read the live data from the oxygen sensors and make comparisons under various operating conditions. The wiring that leads to the sensor will also be inspected and tested, along with the sensor itself. The technician might also inject fuel into the engine to watch for proper sensor feedback data on the scan tool. 


How serious is this code?

In some cases, a code P0131 will not cause any major drivability problems. But it is common that the problem will lead to a rough engine idle, hesitation, or stalling when you try to accelerate. You might have difficulty starting your vehicle. At the very least, the presence of the check engine light will prevent your vehicle from passing an emissions test. Although your engine is trying to compensate for the lean operating condition, in the long run, engine damage can occur.

Get this checked out soon by a CarAdvise shop, where the work will be guaranteed, and one of our expert techs will review any repair orders.


Related Diagnostic Trouble Codes

P0130 O2 Sensor Circuit Malfunction

P0132 O2 Sensor Circuit High Voltage

P0133 O2 Sensor Circuit Slow Response


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