AutoCodes – GMC – U0078 2014 GMC Sierra

U0078 2014 GMC Sierra Code - Control Module Communication Low Speed CAN Bus Off

Quick Answer

The low-speed General Motor Local Area Network (GMLAN) serial data bus is used to communicate information between the devices. Common causes include Check for more codes, Faulty Control Module, Control Module harness is open or shorted. 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: U0078 2014 GMC Sierra indicates Control Module Communication Low Speed CAN Bus Off.
Common causes: Common causes include Check for more codes, Faulty Control Module, Control Module harness is open or shorted.
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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 336

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 20, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code U0078 2014 GMC Sierra Description

The low-speed General Motor Local Area Network (GMLAN) serial data bus is used to communicate information between the devices. The serial data is transmitted over a single wire to the appropriate devices. The low-speed GMLAN serial data circuits also connect directly to the Data Link Connector (DLC). The Diagnostic Trouble Code (DTC) sets when the device setting the DTC has attempted to establish communications on the serial data circuits more than 3 times in 5 s.

OBDII Code U0078 2014 GMC Sierra - Control Module Communication Low Speed CAN Bus Off - AutoCodes.com — U0078 2014 GMC Sierra Code - Control Module Communication Low Speed CAN Bus Off

What does this mean?

What are the Possible Causes of the DTC U0078 2014 GMC Sierra?

Check for more codes
Faulty Control Module
Control Module harness is open or shorted
Control Module circuit poor electrical connection

How to Fix the DTC U0078 2014 GMC Sierra?

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 U0078 2014 GMC Sierra 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 U0078 2014 GMC Sierra code?

Need more information on how to fix the U0078 2014 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0078 2014 GMC Sierra code diagnosed by a professional: Find a repair shop in your area

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 U0078 2014 GMC Sierra Code

What does the OBDII code U0078 mean for a 2014 GMC Sierra?

U0078 indicates a communication issue on the low-speed Controller Area Network (CAN) bus, meaning that one or more control modules are unable to communicate properly.

What are common symptoms associated with the U0078 code?

Common symptoms may include warning lights on the dashboard, erratic behavior of vehicle systems, loss of communication with some control modules, and potential issues with vehicle performance.

What could cause the U0078 code to trigger?

Possible causes include a faulty control module, damaged wiring or connectors on the low-speed CAN bus, poor ground connections, or interference from other electrical components.

How can I diagnose the issue related to the U0078 code?

Begin by scanning the vehicle for additional trouble codes, visually inspecting the wiring and connectors for damage, and checking the grounding points. You may also test the affected control modules to ensure they are functioning properly.

What repairs are commonly needed for code U0078?

Repairs often involve fixing or replacing damaged wiring or connectors, repairing faulty control modules, or addressing grounding issues in the vehicleâ€™s electrical system.

Can I drive my GMC Sierra with the U0078 code?

While it may be possible to drive the vehicle, it's not recommended as it could lead to further complications or safety issues due to malfunctioning systems.

Is it necessary to reset the code after repairs?

Yes, after repairs are made, the code should be cleared using an OBDII scanner, and the vehicle should be test-driven to ensure the issue is resolved and the code does not return.

How can I prevent future occurrences of the U0078 code?

To prevent future issues, regularly inspect the vehicle's wiring and connectors for wear, ensure proper grounding, and address any electrical issues promptly.

Will a battery disconnection help with the U0078 code?

Disconnecting the battery may temporarily reset the vehicleâ€™s systems, but it is unlikely to resolve the underlying issue causing the U0078 code. Proper diagnosis and repair are necessary for a lasting solution.