OBD-II Trouble Code Description for P0178 Subaru

Fuel Composition Sensor Circuit Low

What does this mean?

OBD2 Code P0178 Subaru definition:
Fuel Composition Sensors are used to determine the amount of ethanol alcohol in the gasoline. Normally, a gasoline engine should not have more than 10% ethanol alcohol in the fuel for proper operation. Some vehicles have a flexi-fuel system on them that allow them to run on up to 85% ethanol alcohol in the fuel. The fuel composition sensor sends a frequency modulated signal to the engine controller which is proportional to the alcohol content of the fuel. The injector pulse width and the ignition timing are modified for the increased alcohol content. It takes almost twice the amount of alcohol compared to gasoline to produce the same power.

Symptoms

Possible sumptoms of OBD code P0178 Subaru
– Engine Light ON (or Service Engine Soon Warning Light)

Causes

Possible causes of OBD code P0178 Subaru
– Open or short in FF sensor VPWR circuit – Open in battery ground to FF sensor circuit – Open in FF sensor signal circuit – Short to ground in FF sensor signal circuit – Fuel contamination – Short to VPWR in FF sensor batte

Possible Solutions