AutoCodes – Generic – P0177

P0177 Code - Fuel Composition Sensor Circuit Range/Performance

Quick Answer

Fuel Composition Sensors are used to determine the amount of ethanol alcohol in the gasoline. Common causes include 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. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0177 indicates Fuel Composition Sensor Circuit Range/Performance.
Common causes: Common causes include 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.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 26,971

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 14, 2020

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0177 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 P0177 - Fuel Composition Sensor Circuit Range/Performance - AutoCodes.com — P0177 Code - Fuel Composition Sensor Circuit Range/Performance

What does this mean?

What are the Possible Causes of the DTC P0177?

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

How to Fix the DTC P0177?

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

What does this mean?

Code Tech Notes

Replaced Fuel Composition Sensor

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0177 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0177 code?

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Need Help with the Code?

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Information for Specific Makes

P0177 Mercedes-Benz — Fuel Composition Sensor Circuit Range/Performance

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.