Is it safe to drive with this code?

It depends on which body control functions are affected—loss of lighting or door locks can pose safety concerns. Symptoms vary by vehicle, so if critical systems such as exterior lights or instrument warnings are compromised, it may be advisable to avoid driving until repaired (see our site disclaimer).

U0027 itself is a communication fault, but if it causes the malfunction indicator lamp (MIL) to remain illuminated at the time of test, that may affect the MOT outcome. What ultimately matters is whether the MIL is on during the test—see our disclaimer for details.

Roughly how much does it cost to fix?

If the issue is wiring or connector-related, costs are typically in the low to mid three-figure range (including 2–3 hours of labour). If a body control module requires replacement and programming, expect mid to high three-figure sums or potentially four-figure costs at main dealers. Variation depends on whether the fault lies in accessible wiring versus an internal module defect, and whether you use an independent specialist or franchised workshop.

Can I just clear the code and keep driving?

Clearing the code without repairing the underlying short circuit will typically result in it returning immediately or shortly after, because the physical fault—such as chafed wiring or a damaged transceiver—remains present and continues to disrupt the network.

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← All fault codes | Electrical & Sensors

U0027

Network

Low Speed CAN Communication Bus (-) shorted to Bus (+)

The low-speed CAN communication network has detected an internal short circuit where the negative and positive data lines are electrically connected together, disrupting communication between body control modules.

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ⓘ Information only. This page provides general educational information about fault code U0027. 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 U0027 mean?

U0027 is a Network (CAN bus, module communications) fault code. It indicates: Low 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.

U0027 is one of 4,010 codes in this category. Browse all Electrical & Sensors codes →

What we know about U0027 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 U0027.

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 U0027 in the U-code series. Many fault codes appear together with their neighbours because they relate to the same circuit or component.

U0001 High Speed CAN Communication Bus

U0009 High Speed CAN Communication Bus (-) shorted to Bus (+)

U0018 Medium Speed CAN Communication Bus (-) shorted to Bus (+)

U0029 Vehicle Communication Bus A - Fault

U0036 Vehicle Communication Bus A (-) shorted to Bus A (+)

U0045 Vehicle Communication Bus B (-) shorted to Bus B (+)

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Spotted an issue or have something to add? Mechanics, technicians, and drivers who have first-hand experience with U0027 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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