P0179 OBD-II Trouble Code: Fuel Composition Sensor Circuit High Input

Check Engine Light

P0179 code definition

Fuel Composition Sensor Circuit High Input

What the P0179 code means

P0179 is a generic OBD-II code that is triggered by high input from the diesel fuel sensor, typically indicating a shorted circuit in the sensor. or wiring to the sensor

What causes the P0179 code?

  • The engine control module (ECM) detects excessive sensor circuit input on the high end of the specifications

  • The ECM detects high circuit input if the wiring or connection to the sensor is shorted, which could be the result of fuel contamination of the connection or sensor, or melted wiring shorting the sensor wires together

What are the symptoms of the P0179 code?

  • The Water in Fuel Light illuminates on the instrument cluster

  • The ECM sets code P0179 to memory and triggers the Check Engine Light

  • Excessive water in the fuel could cause engine running problems if the sensor cannot detect it

How does a mechanic diagnose the P0179 code?

  • Scans codes and documents the freeze frame data, then clears the codes to verify code returns

  • Does a visual check of all the wiring and connections to the sensor to check for shorts in the wiring or connections

  • Disconnects the connection to the sensor and checks to see if the sensor connection is corroded or contaminated, which could cause a short

Common mistakes when diagnosing the P0179 code

Follow these simple guidelines to prevent misdiagnosis:

  • Do a visual check of connections to the sensor to make sure they are making good contact. The connection may be shorted from someone not securing it properly after servicing the filter, and the pins could be bent on the sensor or connector.

  • Disconnect the sensor connector and retest the system; if code P0179 is gone and replaced with code P0178 or P0177, that’s an indication that the wiring is not shorted.

How serious is the P0179 code?

  • You will have engine starting and running issues if excessive water is in the fuel and the sensor cannot detect it

  • The engine may misfire, hesitate and stall if excessive water is in the fuel

  • If there is no problems with the fuel then the only issue will be the check engine and water in fuel light will be on.

What repairs can fix the P0179 code?

  • Draining off the water in the fuel filter and clearing Check Engine Light codes
  • Replacing the shorted defective sensor
  • Repairing the short circuit or burned wiring or connection to the sensor
  • Replacing the fuel filter housing with the sensor and clearing the codes

Additional comments for consideration regarding the P0179 code

Not many manufactures use code P0179; it’s only an indicator of water in the fuel and may be damaged by fuel additives. The code can be triggered by wiring shorts, or connector shorts.

Need help with a P0179 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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