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P0176

Fuel Composition Sensor Circuit Malfunction

The ECU detects an electrical fault in the flex-fuel composition sensor circuit. The sensor measures ethanol content (E0–E85) in the fuel; signal missing, shorted or out of plausible range.

  • Check engine light: Yes
  • Emissions related: Yes
  • Repair difficulty: medium

Common causes

Ordered by how often each turns out to be the cause.

  • Flex-fuel sensor failedCommon
  • Wiring or connector faultPossible

Parts involved

  • Flex Fuel Composition Sensor
  • Sensor Wiring

P0176 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.