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P0129 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 are important markers of possible problems inside a vehicle’s systems in the field of automobile diagnostics. One such DTC (Diagnostic Trouble Code) that has to do with Barometric Pressure being too low is P0129. Maintaining the performance of your automobile and accurately identifying any underlying issues require understanding the consequences and meaning of P0129.


The P0129 code indicates a condition where an engine control module (ECM) determines that the barometric pressure in the exhaust manifold is too small to be able to regulate it properly. The barometric pressure sensor is responsible for measuring the air pressure outside the engine, helping the ECM optimize fuel and air mixtures for various driving conditions.


The P0129 error code may be caused by a number of things:

  • Faulty Barometric Pressure Sensor: If the barometric pressure sensor is malfunctioning, the ECM may get erroneous values.
  • Atmospheric Conditions: Barometric pressure readings can be impacted by abrupt changes in the weather, such as high altitude or severe weather fluctuations.
  • Wire Issues: Signal interruptions may result from corroded or damaged wires that connect the barometric pressure sensor to the ECM.
  • Connector problems: Corroded or loose connectors might prevent the sensor and ECM from properly communicating.
  • ECM Malfunction: The P0129 error code can occasionally be caused by the Engine Control Module itself.


You could notice a number of symptoms when the P0129 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 improper fuel and air mixture changes, the engine may show reduced power, hesitancy, or rough idling.
  • Reduced Fuel Efficiency: Suboptimal fuel-to-air ratios might be the consequence of incorrect barometric pressure readings, which can affect fuel efficiency.
  • Poor Throttle Response: The vehicle’s throttle response may be irregular or erratic.


A methodical strategy is needed to correctly identify the P0129 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 P0129 code may be read and retrieved from the vehicle’s ECM using an OBD-II scanner.
  • Visual Inspection: To find any obvious problems, the barometric pressure sensor, it’s wiring, and its connections must all be carefully examined visually.
  • Testing the Barometric Pressure Sensor: A multimeter should be used to measure the voltage output of the sensor to evaluate its performance.
  • Examining Atmospheric Conditions: To verify the sensor’s results, the technician may take into account the current weather, particularly at higher elevations.

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 barometric pressure sensor without first testing it: Before contemplating a replacement, the sensor must be functionally tested.
  • Ignoring Atmospheric Conditions: During diagnosis, extreme weather conditions should be considered since they may affect the sensor’s data.

How serious is this?

The seriousness of P0129 is dependent on a number of factors. However, it can become a minor inconvenience and may lead to engine performance problems or reduced fuel consumption if the issue remains unresolved. It is recommended to diagnose and repair the condition rapidly, with a view to avoiding additional complications.

What repairs can fix the code?

repair manuals

The following remedies can be made if the P0129 code’s underlying cause has been found:

  • Replacement of the barometric pressure sensor: If the sensor is broken, a comparable and superior replacement should be used.
  • Fixing wires and connections: If required, damaged wires or connections should be fixed or replaced.
  • Addressing Atmospheric Conditions: If the sensor’s readings are affected by severe weather, no repairs could be necessary. Instead, the ECM may adjust the parameters for the fuel and air mixtures correspondingly.

Related codes

Occasionally, other DTCs might accompany the P0129 code, providing additional insights into related issues. Commonly related codes include P0107 (Manifold Absolute Pressure/BARO Sensor Low Input) and P0108 (Manifold Absolute Pressure/BARO Sensor High Input).


In conclusion, the P0129 DTC code indicates potential problems with the barometric pressure sensor, specifically indicating low pressure. Understanding the meaning, causes, symptoms, and appropriate repairs can help you address the issue effectively. 

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. In order to keep your vehicle in excellent condition, ensure that the correct diagnosis and safe repair are carried out by a skilled mechanic.

P0129 Code – What Does It Mean & How To Fix It