U0018
NetworkMedium Speed CAN Communication Bus (-) shorted to Bus (+)
The medium-speed CAN communication bus has detected a short circuit between its negative and positive signal wires, which may disrupt communication between control modules in the vehicle.
ⓘ Information only. This page provides general educational information about fault code U0018. 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 U0018 mean?
U0018 is a Network (CAN bus, module communications) fault code. It indicates: Medium Speed CAN Communication Bus (-) shorted to Bus (+).
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 Electrical & Sensors codes
Codes in the Electrical & Sensors category.
U0018 is one of 4,010 codes in this category. Browse all Electrical & Sensors codes →
What we know about U0018 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 U0018.
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 U0018 in the U-code series. Many fault codes appear together with their neighbours because they relate to the same circuit or component.
Other Electrical & Sensors codes
Other fault codes in the same system as U0018. 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 U0018 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 →