AutoCodes – GMC – U0078 2015 GMC Sierra

U0078 2015 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 2015 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 595

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 2015 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 2015 GMC Sierra - Control Module Communication Low Speed CAN Bus Off - AutoCodes.com — U0078 2015 GMC Sierra Code - Control Module Communication Low Speed CAN Bus Off

What does this mean?

What are the Possible Causes of the DTC U0078 2015 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 2015 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 2015 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 2015 GMC Sierra code?

Need more information on how to fix the U0078 2015 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0078 2015 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 2015 GMC Sierra Code

1. What does OBDII code U0078 on a 2015 GMC Sierra mean?

The code U0078 indicates a communication problem with the Control Module Communication Low Speed CAN Bus Off in the vehicle.

2. What are the common symptoms of OBDII code U0078 in a 2015 GMC Sierra?

Common symptoms include intermittent or complete loss of communication with various control modules, warning lights on the dashboard, and issues with vehicle systems like power windows, door locks, or lights.

3. What are the possible causes of OBDII code U0078 in a 2015 GMC Sierra?

Potential causes include damaged wiring or connectors in the CAN bus system, a faulty control module, software issues, or even water damage to the vehicle's electronic components.

4. How can I diagnose the OBDII code U0078 on a 2015 GMC Sierra?

Diagnosing this code typically involves using a professional OBDII scanner to check for other related trouble codes, inspecting the wiring and connectors in the CAN bus system, and testing the control modules for proper communication.

5. Is it safe to drive with OBDII code U0078 present in a 2015 GMC Sierra?

It is generally not recommended to drive the vehicle with this code active, as it can lead to unpredictable behavior of various vehicle systems and potentially compromise safety.

6. Can I repair OBDII code U0078 in a 2015 GMC Sierra myself?

Repairing this code may require advanced diagnostic skills and specialized tools. It is recommended to consult with a qualified mechanic or dealership for proper diagnosis and repair.

7. How much does it cost to fix OBDII code U0078 on a 2015 GMC Sierra?

The cost of repairing this code can vary depending on the exact cause of the issue. It may involve replacing damaged wiring, connectors, or control modules, which can range from a few hundred to a few thousand dollars.

8. Will resetting the OBDII code U0078 on a 2015 GMC Sierra make it go away permanently?

Simply resetting the code without addressing the underlying issue will likely result in it reappearing once the vehicle is driven again. It is important to diagnose and fix the root cause of the problem to prevent the code from coming back.

9. Can extreme weather conditions cause OBDII code U0078 to trigger in a 2015 GMC Sierra?

Yes, extreme weather conditions such as severe heat or cold can potentially affect the electronic components and wiring in the vehicle, leading to communication issues and triggering code U0078.

10. How long does it take to repair OBDII code U0078 in a 2015 GMC Sierra?

The repair time for this code can vary depending on the specific cause and complexity of the issue. It may take anywhere from a few hours to a full day or more to diagnose and fix the problem successfully.