AutoCodes – GMC – U0028 GMC

U0028 GMC Code - Media Oriented Systems Transport Bus

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 GMC indicates Media Oriented Systems Transport Bus.
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 4,226

How popular is this code, among other codes? Low

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 GMC 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 GMC - Media Oriented Systems Transport Bus - AutoCodes.com — U0028 GMC Code - Media Oriented Systems Transport Bus

What does this mean?

What are the Possible Causes of the DTC U0028 GMC?

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

How to Fix the DTC U0028 GMC?

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 GMC 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.

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Information for Specific GMC Models

U0028 2014 GMC Sierra — Media Oriented Systems Transport Bus
U0028 2015 GMC Sierra — Media Oriented Systems Transport Bus
U0028 2016 GMC Sierra — Media Oriented Systems Transport Bus
U0028 2017 GMC Sierra — Media Oriented Systems Transport Bus
U0028 2018 GMC Sierra — Media Oriented Systems Transport Bus

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 GMC Code

1. What is OBDII code U0028 in a GMC vehicle?

- OBDII code U0028 in a GMC vehicle indicates a problem with the Media Oriented Systems Transport (MOST) Bus communication system.

2. What are the common symptoms of OBDII code U0028 in a GMC?

- Common symptoms of OBDII code U0028 in a GMC include issues with the vehicle's infotainment system, radio, navigation, or other media-related functions.

3. What are the possible causes of OBDII code U0028 in a GMC?

- Possible causes of OBDII code U0028 in a GMC include a faulty MOST Bus control module, damaged wiring or connectors, or issues with the media devices connected to the bus.

4. How can I diagnose OBDII code U0028 in a GMC?

- Diagnosing OBDII code U0028 in a GMC typically involves using a diagnostic scan tool to retrieve the specific fault codes, checking the MOST Bus system for faults, and inspecting the wiring and connectors for any damage.

5. What are some repair tips for fixing OBDII code U0028 in a GMC?

- Repair tips for fixing OBDII code U0028 in a GMC may include repairing or replacing damaged wiring, connectors, or components in the MOST Bus system, resetting the system, or updating software if available.

6. Can OBDII code U0028 in a GMC be fixed at home?

- While diagnosing and repairing OBDII code U0028 in a GMC may be possible for experienced DIYers, it is recommended to seek professional help for accurate diagnosis and proper repair to avoid causing further damage.

7. Is it safe to continue driving with OBDII code U0028 in a GMC?

- It is not recommended to continue driving with OBDII code U0028 in a GMC as it can lead to further issues with the vehicle's media system and potentially affect other electronic functions in the vehicle.

8. How much does it cost to repair OBDII code U0028 in a GMC?

- The cost to repair OBDII code U0028 in a GMC can vary depending on the specific cause of the issue, the extent of the damage, and labor costs. It is advisable to get a few quotes from reputable repair shops for an accurate estimate.

9. Can OBDII code U0028 in a GMC cause other problems in the vehicle?

- OBDII code U0028 in a GMC primarily affects the media system, but if left unresolved, it can potentially cause issues with other electronic systems in the vehicle due to the interconnected nature of modern vehicle systems.

10. How can I prevent OBDII code U0028 from recurring in my GMC?

- To prevent OBDII code U0028 from recurring in your GMC, it is important to address any underlying issues promptly, perform regular maintenance checks on the media system components, and avoid overloading the MOST Bus network with incompatible devices.