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P0179 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.


The DTC P0179 code is indicating a problem with the fuel composition sensor circuit on Bank 2 of the engine. Bank 2 shall generally refer to the engine’s right side, in reverse of cylinder 1. It must be borne in mind that this code is applied exclusively to some vehicles and does not cover all types or models. For precise interpretation, it is essential that the vehicle’s documentation or advice of an automotive expert be consulted.


The gasoline composition sensor in Bank 2 may be delivering aberrant or unpredictable voltage signals to the vehicle’s powertrain control module (PCM) or engine control module (ECM) when the P0179 code is activated. The fuel composition sensor measures the amount of ethanol in the gasoline; a broken sensor might result in incorrect fuel calculations and impair engine performance.


The P0179 DTC code may appear as a result of several factors:

  • Fuel composition sensor malfunction: The fuel composition sensor may be faulty and give out the wrong voltage values.
  • Wire Problems: Corroded or damaged wire in the gasoline composition sensor circuit might interfere with the signal’s delivery, resulting in readings that are inconsistent.
  • Variability in Ethanol Level: The accuracy of the fuel composition sensor’s measurements can be impacted by variations in the fuel’s ethanol level.
  • ECM/PCM Issues: The gasoline composition sensor may give incorrect readings if there is an issue with the vehicle’s engine control module or powertrain control module.


The following signs and symptoms might be present when the P0179 DTC code is present:

  • Illuminated Check Engine Light: The most noticeable symptom is the illumination of the check engine light on the vehicle’s dashboard.
  • Reduced gasoline efficiency: A faulty gasoline composition sensor might result in incorrect fuel estimates, which decreases fuel efficiency.
  • Problems with the engine’s performance: The car might have rough idling, stuttering, or a lack of power when accelerating.
  • Emissions Issues: Due to erroneous fuel mixture calculations, the vehicle may fail an emissions test.


A competent technician must use a methodical methodology to accurately diagnose the P0179 DTC code. The diagnostic procedure might entail:

  • OBD-II Scanner: Using an OBD-II scanner, the mechanic can retrieve the trouble code and other relevant data from the vehicle’s onboard computer.
  • Visual Inspection: The fuel composition sensor and its wiring should be carefully inspected visually for any damage or corrosion that is readily apparent.
  • Checking the gasoline Composition Sensor: The technician may do experiments to see how the sensor responds to variations in the amount of ethanol in the gasoline and how much voltage it outputs.
  • Resolving associated Problems: Prior to concentrating on the fuel composition sensor examination, it is crucial to resolve any fuel quality issues or other associated issues.

Common mistakes

Common errors to avoid when handling the P0179 code include:

  • Ignoring Other Codes: P0179 could be accompanied by other relevant codes, and ignoring them could result in missing important problems.
  • Replacing parts too soon: To prevent wasting money, it’s important to undertake a thorough diagnosis before replacing any components.
  • Ignoring Ethanol Content Variability: It’s critical to comprehend the ethanol content variability in the gasoline when interpreting the signals from the fuel composition sensor.

How serious is this?

The importance of the P0179 DTC code depends on different factors, such as the extent of the problem and road conditions. While the vehicle may still be operable with the code present, ignoring it can lead to reduced fuel efficiency and potential engine performance issues.

What repairs can fix the code?

repair manuals

The P0179 DTC code can be fixed using the following fixes, depending on the diagnosis:

  • Replacing the Fuel Composition Sensor: If the fuel composition sensor is broken, it may be fixed by swapping it out for a brand-new, working one.
  • Repairing wire: The gasoline composition sensor circuit can be made operational again by repairing any corroded or broken wire.
  • Ethanol Content Management: Monitoring and managing the variability of ethanol content in the fuel can improve the accuracy of the fuel composition sensor’s readings.

Related codes

Other related DTC codes include P0176 (Fuel Composition Sensor Circuit Malfunction Bank 1) and P0178 (Fuel Composition Sensor Circuit High Input Bank 1). These codes may provide additional insights into the fuel composition sensor’s overall performance.


The P0179 DTC code indicates that in Bank 2, the engine’s fuel composition sensor may have an issue. In order to maintain optimal engine performance, fuel efficiency, and emissions compliance, it is crucial that a quick diagnosis and corrective action are carried out. In order to ensure a smooth and troubleless driving experience, if you have encountered this code, it is recommended that you seek the assistance of an expert for accurate diagnosis and repair.

P0179 Code – What Does It Mean & How To Fix It