Diagnostic trouble code P0131 is defined as “O2 Sensor Circuit Low Voltage Bank 1 Sensor 1.” It indicates a low voltage signal from the front oxygen sensor, which monitors the oxygen concentration of the raw exhaust gas.
DTC P0131 implies a fault in the heated oxygen sensor (HO2S) located near the exhaust manifold on Bank 1, before the catalytic converter (Bank 1 is the engine side with cylinder #1.)
The P0131 code is triggered when the Engine Control Module (ECM) or Powertrain Control Module (PCM) detects a low voltage condition or an unbalanced air-fuel ratio.
A low voltage signal means more oxygen in the air-fuel ratio (that is, the engine is running lean.) So, the ECM or PCM compensates for the issue by adjusting the fuel trim values. But while this attempt at fuel control may seem like a fix, it can lead to performance inefficiencies.
A P0131 trouble code or faulty oxygen sensor circuit may be accompanied by signs such as:
Note: If another fault code is present in addition to the P0131 code, there may be different or additional symptoms.
Yes, your vehicle may still function (for a while) with a DTC P0131. However, this trouble code is a serious issue and should be addressed immediately.
Extended driving with a low voltage signal from the oxygen sensor circuit can lead to:
If you don’t address the issue, the problem will only worsen with time, and the repair costs will drastically increase. So, get this Check Engine Light code addressed as soon as possible.
Here are the potential causes of a code P0131:
Here are steps a mechanic would take to diagnose error code P0131:
Some additional checks the mechanic may do include a review of coolant temperature sensor issues, low fuel pressure, and vacuum or exhaust leaks.
A complete diagnosis can help prevent unnecessary replacements, saving costs on your repairs. For example, engine misfires could also lead to improper O2 sensor readings, which means the O2 sensor isn’t faulty and it’s something else that needs a fix.
Here are some possible repairs related to code P0131:
Note: If any other codes are present with trouble code P0131, the mechanic will resolve them before this O2 sensor code to prevent a misdiagnosis.
Since this fault code can be triggered for several reasons, a mechanic will need to conduct a full diagnosis to identify the issue and potential repair costs. The diagnosis may cost between $75-$150, depending on your mechanic’s labor rate.
Here are estimates for replacing relevant parts (including the cost of labor):
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