Code Definition

P0179 — Fuel Composition Sensor Circuit High Input

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0179

P0179 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0179 is stored, the module has detected a signal or supply voltage higher than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0179 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0179 fault code is set when the Engine Control Module (ECM) detects a higher than expected input signal from the fuel composition sensor circuit. This sensor is important in flexible fuel vehicles, as it determines the composition of the fuel (like the ratio of gasoline to ethanol). The ECM uses this information to appropriately adjust the air-fuel mixture and ignition timing. A high input signal might indicate a malfunction within the sensor, issues in the wiring or connectors, or a short to power in the sensor circuit. This condition can lead to the ECM receiving inaccurate data about t...

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