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P0143 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


Trouble codes serve as essential indicators of possible problems with the vehicle’s systems in automotive diagnostics. One of these codes is the P0143 DTC Diagnostic Trouble Code, which applies to a low-voltage oxygen sensor circuit in Bank 1 Sensor 3. To maintain your vehicle’s performance and identify problems that may have arisen, you need to understand the meaning and implications of P0143.


In particular, the P0143 indicator indicates that a low voltage condition exists in the Oxygen Sensor O2 line for Bank 1 sensor number 3. After leaving the engine, the oxygen content of the exhaust gases will be monitored by the O2 sensor. This data shall be essential to adjusting the mixture of air-fuel and optimizing engine performance for the Engine Control Module, ECM.


The P0143 error code may appear for several reasons:

  • Faulty Oxygen Sensor: If the O2 sensor is malfunctioning, the ECM may get inaccurate voltage values.
  • Wire Issues: Low voltage signals might be brought on by corroded or damaged wire that connects the O2 sensor to the ECM.
  • Connector problems: The transmission between the O2 sensor and the ECM may be hampered by loose or damaged connectors.
  • Exhaust System Leaks: Sensor readings may be impacted by any leaks in the exhaust system that are present before the O2 sensor.
  • ECM Malfunction: The P0143 error code can occasionally be caused by the Engine Control Module itself.


You could notice a number of symptoms when the P0143 code is activated that point to possible problems with your car:

  • Illuminated Check Engine Light: The most apparent sign of a trouble code, the check engine light is activated.
  • Decreased Engine Performance: Due to faulty air-fuel mixture changes, the engine may show lower power, hesitancy, or rough idling.
  • Higher Emissions: Inaccurate O2 sensor readings might result in higher emissions, which could cause the car to fail emission tests.


A methodical strategy is needed to correctly identify the P0143 code’s root cause. The following diagnostic procedures can be carried out by a skilled mechanic or an OBD-II scanner:

  • Checking for Codes: The P0143 code may be read and retrieved from the vehicle’s ECM using an OBD-II scanner.
  • Visual Inspection: To find any obvious problems, the O2 sensor’s wiring and connections must be thoroughly inspected visually.
  • Testing the Oxygen Sensor: The voltage output of the sensor should be measured with a multimeter to determine its performance.
  • Examining the Exhaust System for Leaks: If the exhaust system has leaks, the readings from the O2 sensor may be off.

Common mistakes

Some typical errors can happen during diagnostics and repairs, resulting in inaccurate or inefficient fixes:

  • Ignoring wire and Connectors: A loose connector or broken wire is frequently the cause of problems but is frequently disregarded.
  • Replacing the oxygen sensor without testing: Before contemplating a replacement, the sensor’s functionality must be properly tested.
  • Ignoring Exhaust System Leaks: Since exhaust system leaks might alter O2 sensor readings, they should be fixed.

How serious is this?

The seriousness of the P0143 code is dependent on a number of factors. While this could be a small inconvenience, it can cause engine performance problems and higher emissions if the problem is not resolved. In order not to develop further complications, it is advisable to diagnose and repair the problem immediately.

What repairs can fix the code?

repair manuals

The following remedies can be made if the P0143 code’s underlying cause has been found:

  • Replacement of the oxygen sensor: If the sensor is broken, a suitable and superior replacement should be used.
  • Fixing wires and connections: If required, damaged wires or connections should be fixed or replaced.
  • Repairing Exhaust Leaks: To stop the entry of outside air, any leaks in the exhaust system before the O2 sensor should be patched.

Related codes

Occasionally, other DTCs might accompany the P0143 code, providing additional insights into related issues. Commonly related codes include P0138 (Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2) and P0139 (Oxygen Sensor Circuit Slow Response Bank 1 Sensor 2).


Finally, the P0143 DTC code indicates that there is a potential issue with the Oxygen sensor circuit’s low voltage in Bank 1 Sensor 3. You can help address this issue in an efficient manner by knowing its meaning, causes, symptoms, and appropriate treatment. 

Swift diagnosis and proper fixes will not only clear the code but also ensure your vehicle operates optimally, leading to a smoother and more efficient driving experience. To keep your car in excellent condition, always seek the advice of a qualified mechanic who will provide you with an accurate diagnosis and safe repairs.

P0143 Code – What Does It Mean & How To Fix It