AutoCodes – Generic – U0028

U0028 Code - Vehicle Communication Bus 'A'

Quick Answer

The Media Oriented Systems Transport (MOST) bus consists of a physical ring in which multimedia devices share audio, video and infotainment system control data. Common causes include Faulty Audio Unit (Radio), Audio Unit harness is open or shorted, Audio Unit circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: U0028 indicates Vehicle Communication Bus 'A'.
Common causes: Common causes include Faulty Audio Unit (Radio), Audio Unit harness is open or shorted, Audio Unit circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 41,087

How popular is this code, among other codes? Medium

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 19, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0028 Description

The Media Oriented Systems Transport (MOST) bus consists of a physical ring in which multimedia devices share audio, video and infotainment system control data. Each device on the MOST bus transmits and receives data via the MOST Bus Serial Data (+/- transmit/receive) circuits. The MOST bus diagnostic master is the Radio. The MOST control circuit is connected to each device on the MOST bus. Each device provides a 12 V signal on the MOST control circuit. The Radio initiates communication on the MOST bus at Ignition ON by toggling the MOST control circuit low for 100 ms. Once each device recognizes the wakeup signal from the Radio on the MOST control circuit, they will respond to the Radio on the MOST bus to indicate no faults are present and normal communications will commence. The Diagnostic Trouble Code (DTC) sets when a fault occurs on transmit, receive, electronic control lines, or internal device failure.

OBDII Code U0028 - Vehicle Communication Bus 'A' - AutoCodes.com — U0028 Code - Vehicle Communication Bus 'A'

What does this mean?

What are the Possible Causes of the DTC U0028?

Faulty Audio Unit (Radio)
Audio Unit harness is open or shorted
Audio Unit circuit poor electrical connection

How to Fix the DTC U0028?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0028 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the U0028 code?

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Need Help with the Code?

Get the U0028 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U0028 Acura — F-CAN Communication Circuit Error
U0028 Buick — Media Oriented Systems Transport Bus
U0028 Cadillac — Media Oriented Systems Transport Bus
U0028 Chevrolet — Media Oriented Systems Transport Bus
U0028 Ford — Vehicle Communication Bus 'A' Bus Off
U0028 GMC — Media Oriented Systems Transport Bus
U0028 Honda — F-CAN Communication Circuit Error
U0028 Lincoln — Vehicle Communication Bus 'A' Bus Off
U0028 Mercury — Vehicle Communication Bus 'A' Bus Off

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about U0028 Code

1. What is OBDII code U0028 related to Vehicle Communication Bus 'A'?

Code U0028 indicates a communication problem on the Vehicle Communication Bus 'A' within the vehicle's network.

2. What are common symptoms of OBDII code U0028?

Common symptoms of code U0028 may include issues with various vehicle systems such as the transmission, engine, ABS, or airbag systems. The vehicle may also experience communication errors with diagnostic tools.

3. What are possible causes of OBDII code U0028?

Potential causes of code U0028 include faulty wiring or connectors in the Vehicle Communication Bus 'A', a defective control module, software issues, or a problem with the network communication system.

4. How is OBDII code U0028 diagnosed?

Diagnosing code U0028 typically involves using a diagnostic scanner to retrieve the specific fault codes, checking the wiring and connectors in the Vehicle Communication Bus 'A', and testing the communication between control modules.

5. How can OBDII code U0028 be repaired?

Repairing code U0028 may involve repairing or replacing damaged wiring or connectors in the Vehicle Communication Bus 'A', reprogramming control modules, or addressing any underlying issues that may have caused the communication error.

6. Can OBDII code U0028 cause the vehicle to fail an emissions test?

Yes, if left unresolved, code U0028 can affect the proper functioning of emissions-related systems in the vehicle, potentially leading to a failed emissions test.

7. Is it safe to continue driving with OBDII code U0028 present?

It is not recommended to continue driving with unresolved code U0028, as it may lead to further communication errors between critical vehicle systems, affecting overall performance and safety.

8. Can a DIY enthusiast fix OBDII code U0028 at home?

While some basic troubleshooting steps can be performed at home, resolving code U0028 often requires advanced diagnostic tools and expertise, making it advisable to seek professional help for proper repair.

9. How long does it typically take to repair OBDII code U0028?

The time needed to repair code U0028 can vary depending on the underlying cause and complexity of the issue. In some cases, repairs can be completed within a few hours, while more intricate problems may take longer to resolve.

10. Are there any preventative measures to avoid OBDII code U0028 in the future?

To help prevent code U0028 from occurring, regular maintenance checks, including inspecting wiring harnesses and connectors, ensuring software is up to date, and addressing any communication issues promptly, can be beneficial.