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P0177 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 fuel composition sensor circuit in Bank 1 of the engine is thought to be malfunctioning, according to the P0177 DTC code. Typically, Bank 1 refers to the side of the engine that houses Cylinder 1. This code is unique to particular makes and models of automobiles, thus it might not apply to all of them. For a correct interpretation, consulting the vehicle’s manual or consulting with an automotive professional is necessary.


The fuel composition sensor in Bank 1 is giving aberrant or unpredictable voltage signals to the engine control module (ECM) or powertrain control module (PCM) of the vehicle when the P0177 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 P0177 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.


When the P0177 DTC code is present, the following symptoms may be observed:

  • 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 P0177 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 working with the P0177 code include:

  • Ignoring Other Codes: P0177 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 seriousness of the P0177 DTC code depends upon a number of factors such as the degree of difficulty and driving 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 P0177 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) and P0178 (Fuel Composition Sensor Circuit High Input). These codes may provide additional insights into the fuel composition sensor’s overall performance.


Potential issues with the fuel composition sensor at Bank 1 of the engine are identified by the P0177 DTC code. In order to maintain optimum engine performance, fuel efficiency, and emissions compliance it is essential that you diagnose the problem immediately and fix the problem as soon as possible. In order to provide a pleasant and trouble-free driving experience, if you encounter this code, it is recommended that you seek professional help with your problem in order to be properly diagnosed and resolved.

P0177 Code – What Does It Mean & How To Fix It