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P0178 Mercedes-Benz Code - Fuel Composition Sensor Circuit Low Input

- Code Popularity: 7,119 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P0178 Mercedes-Benz?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other 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
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How to Fix the DTC P0178 Mercedes-Benz?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Code Tech Notes

Replaced Fuel Composition Sensor

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0178 Mercedes-Benz code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

Code P0178 Mercedes-Benz Description

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 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.

OBDII Code P0178 Mercedes-Benz - Fuel Composition Sensor Circuit Low Input - AutoCodes.com
P0178 Mercedes-Benz Code - Fuel Composition Sensor Circuit Low Input

Need More Information on the Code?

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