What does code P0178 mean?

Q: What does code P0178 mean?

Fuel Composition Sensor Circuit Low. P0178 means the powertrain control module (PCM) has detected a fuel composition sensor signal voltage that is lower than the expected range for the current operating conditions. The sensor, typically a flex-fuel sensor on vehicles designed to run on ethanol blends, reports the ethanol content and temperature of the fuel, and a low signal indicates either a circuit fault or an internal sensor failure.

DTC codes / P01xx · Fuel and air metering / P0178

P0178Fuel Composition Sensor Circuit Low

P0178 means the powertrain control module (PCM) has detected a fuel composition sensor signal voltage that is lower than the expected range for the current operating conditions. The sensor, typically a flex-fuel sensor on vehicles designed to run on ethanol blends, reports the ethanol content and temperature of the fuel, and a low signal indicates either a circuit fault or an internal sensor failure.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.