Is it safe to drive with this code?

In many cases, you may continue short essential journeys, as the fault typically does not trigger limp-mode or immediate power loss. However, reduced fuel economy and rough running can occur, and prolonged driving may risk further issues such as catalytic converter contamination. If you experience stalling, strong petrol smell, or flashing warning lights, stop driving and arrange recovery—see our disclaimer for full guidance.

The outcome depends on whether the malfunction indicator lamp is illuminated at the time of the MOT test. An active MIL can lead to an emissions failure under the OBD check, so it is advisable to have the fault diagnosed and cleared beforehand—refer to our disclaimer for complete MOT information.

Roughly how much does it cost to fix?

Costs vary widely depending on the root cause and where the work is carried out. Simple wiring repairs or connector cleaning may fall into the low two-figure range. Replacing the fuel composition sensor typically sits in the low three-figure bracket, whilst more involved diagnostics and ECM reflashing can reach the mid three-figure range. A full engine control module replacement, if required, may enter four-figure territory. Independent garages often charge less than main dealers, and parts availability affects final bills.

Does this code only affect flex-fuel vehicles?

P0179 is most commonly associated with flexible-fuel (E85-capable) vehicles, where the fuel composition sensor monitors ethanol content. However, some manufacturers may use the code in relation to diesel fuel sensors or other fuel-quality monitoring circuits. Always check your vehicle's service information or consult a technician familiar with your make and model.

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← All fault codes | Fuel System

P0179

Powertrain

Fuel Composition Sensor Circuit High Input

The engine control module has detected an abnormally high voltage signal from the fuel composition sensor circuit, which typically monitors ethanol content in flexible-fuel vehicles.

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ⓘ Information only. This page provides general educational information about fault code P0179. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.

Recommended next steps

Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.

What does P0179 mean?

P0179 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Fuel Composition Sensor Circuit High Input.

This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.

About Fuel System codes

Fuel system codes cover everything from the tank to the injectors: fuel pumps, filters, pressure regulators, rail pressure sensors, and injectors themselves. On modern common-rail diesels these codes can cause hard starting, limp mode, or no-start conditions.

P0179 is one of 469 codes in this category. Browse all Fuel System codes →

What we know about P0179 specifically

We record the SAE J2012 standardised definition and the system this code belongs to, but we have not yet published detailed driver-reported symptoms, common causes, or step-by-step diagnostic guidance for P0179.

Rather than invent that information by generating generic content from a template, we leave it out. For specific guidance, the most reliable sources are:

•your vehicle's own service manual or manufacturer-specific technical bulletins
•a qualified mechanic with a manufacturer-level diagnostic tool
•a marque specialist familiar with your make and model

Codes nearby

Codes adjacent to P0179 in the P-code series. Many fault codes appear together with their neighbours because they relate to the same circuit or component.

P0176 Fuel Composition Sensor Circuit Malfunction

P0177 Fuel Composition Sensor Circuit Range/Performance

P0178 Fuel Composition Sensor Circuit Low Input

P0180 Fuel Temperature Sensor A Circuit Malfunction

P0181 Fuel Temperature Sensor A Circuit Range/Performance

P0182 Fuel Temperature Sensor A Circuit Low Input

Other Fuel System codes

Other fault codes in the same system as P0179. The ones with detailed guides have plain-English explanations, symptoms, causes, and diagnostic steps.

P0087

Fuel Rail/System Pressure - Too Low Detailed guide

P0089

Fuel Pressure Regulator 1 Performance Detailed guide

P0090

Fuel Pressure Regulator Control Circuit/Open Detailed guide

P0100

Mass or Volume Air Flow (MAF) Circuit Malfunction Detailed guide

P0106

Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem Detailed guide

P0170

Fuel Trim Malfunction (Bank 1) Detailed guide

Spotted an issue or have something to add? Mechanics, technicians, and drivers who have first-hand experience with P0179 can submit a correction or expansion. We review every submission before publishing, mechanic submissions are prioritised.

Information only, not professional advice

The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →

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