Is it safe to drive with this code?

In many cases you may be able to drive short distances, particularly if the vehicle defaults to conventional petrol operation, but the alternative fuel system may be disabled or unreliable. The underlying communication fault could potentially affect other systems, so arrange a professional inspection promptly—see our disclaimer for guidance on safe operation.

This code may affect your MOT result if the malfunction indicator lamp is illuminated at the time of the test, as emissions equipment must function correctly. What ultimately matters is whether the warning light is on during the inspection—refer to our disclaimer for MOT-related queries.

Roughly how much does it cost to fix?

Repair costs vary considerably depending on the root cause. If the issue is a simple wiring repair or connector cleaning, expect low three-figure costs; if the alternative fuel control module itself requires replacement or reprogramming, costs may reach mid to high three-figure territory, particularly at franchised dealers. Labour rates differ between independent specialists and main dealers.

Does this code only affect vehicles running on CNG or LPG?

Typically, yes—U0409 is most commonly seen in vehicles equipped with compressed natural gas, liquefied petroleum gas, or certain hybrid powertrains that use a dedicated alternative fuel control module. Conventional petrol or diesel-only vehicles are unlikely to log this code.

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← All fault codes | Fuel System

U0409

Network

Invalid Data Received From Alternative Fuel Control Module

The engine control unit has detected corrupted or implausible data being transmitted from the alternative fuel control module over the vehicle's communication network.

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ⓘ Information only. This page provides general educational information about fault code U0409. 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 U0409 mean?

U0409 is a Network (CAN bus, module communications) fault code. It indicates: Invalid Data Received From Alternative Fuel Control Module.

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.

U0409 is one of 469 codes in this category. Browse all Fuel System codes →

What we know about U0409 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 U0409.

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 U0409 in the U-code series. Many fault codes appear together with their neighbours because they relate to the same circuit or component.

U0406 Invalid Data Received From Fuel Injector Control Module

U0407 Invalid Data Received From Glow Plug Control Module

U0408 Invalid Data Received From Throttle Actuator Control Module

U040B Invalid Data Received From Exhaust Gas Recirculation Control Module "A"

U040C Invalid Data Received From Exhaust Gas Recirculation Control Module "B"

U040D Invalid Data Received From Turbocharger/Supercharger Control Module "A"

Other Fuel System codes

Other fault codes in the same system as U0409. 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 U0409 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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