U040B
NetworkInvalid Data Received From Exhaust Gas Recirculation Control Module "A"
The engine control unit has detected that it is receiving corrupted or implausible data from the exhaust gas recirculation control module over the vehicle's communication network.
ⓘ Information only. This page provides general educational information about fault code U040B. 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 U040B mean?
U040B is a Network (CAN bus, module communications) fault code. It indicates: Invalid Data Received From Exhaust Gas Recirculation Control Module "A".
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 Emissions codes
Emissions codes relate to systems that control or monitor exhaust gas composition, catalytic converters, oxygen sensors, exhaust gas recirculation (EGR), and the evaporative emissions (EVAP) system. These rarely affect drivability dramatically but can cause MOT failures.
U040B is one of 258 codes in this category. Browse all Emissions codes →
What we know about U040B 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 U040B.
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 U040B in the U-code series. Many fault codes appear together with their neighbours because they relate to the same circuit or component.
Other Emissions codes
Other fault codes in the same system as U040B. The ones with detailed guides have plain-English explanations, symptoms, causes, and diagnostic steps.
Spotted an issue or have something to add? Mechanics, technicians, and drivers who have first-hand experience with U040B 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 →