OBD Code P0178

Fuel Composition Sensor Circuit Low

What’s mean?

OBD2 Code P0178 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 P0178
– Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

Possible causes of P0178
– 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