P0178 - Fuel Composition Sensor Circuit Low Input
P0178 Possible Causes
- Flexible Fuel (FF) sensor to Vehicle Power (VPWR) circuit harness open or shorted
- FF to VPWR circuit poor electrical connection
- Open in FF sensor signal circuit
- Short to ground in FF sensor signal circuit
- Fuel contamination
- Short to VPWR in FF sensor batte
First diagnose P0178 code
Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
P0178 Tech NotesReplaced Fuel Composition Sensor
Cost of diagnosing the P0178 code
Labor: 1.0The cost of diagnosing the P0178 code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
P0178 Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P0178 DescriptionFuel 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 Flexible Fuel (FF) 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.
P0178 More InformationNeed more information on how to fix the P0178 code?
Get Access to Factory Service Manuals
P0178 Information for specific makes
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