AutoCodes – GMC – U0077 2018 GMC Sierra

U0077 2018 GMC Sierra Code - Control Module Communication Chassis Expansion CAN Bus

Quick Answer

The devices connected to the chassis high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. 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: U0077 2018 GMC Sierra indicates Control Module Communication Chassis Expansion CAN Bus.
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.

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Code Popularity 570

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
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Code U0077 2018 GMC Sierra Description

The devices connected to the chassis high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices when the ignition switch is in any position other than OFF. The chassis high speed GMLAN serial data bus uses terminating resistors that are in parallel with the chassis high speed GMLAN (+) and (-) circuits. The Diagnostic Trouble Code (DTC) sets when a supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U0077 2018 GMC Sierra - Control Module Communication Chassis Expansion CAN Bus - AutoCodes.com — U0077 2018 GMC Sierra Code - Control Module Communication Chassis Expansion CAN Bus

What does this mean?

What are the Possible Causes of the DTC U0077 2018 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 U0077 2018 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 U0077 2018 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 U0077 2018 GMC Sierra code?

Need more information on how to fix the U0077 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 U0077 2018 GMC Sierra Code

1. What does the OBDII code U0077 mean on a 2018 GMC Sierra?

The U0077 code indicates a communication issue on the Control Module Communication Chassis Expansion CAN Bus, which is responsible for connecting various vehicle systems.

2. What are the common symptoms of the U0077 code on a GMC Sierra?

Symptoms may include warning lights on the dashboard, intermittent system failures, loss of functionality in certain components, or no noticeable performance issues depending on the severity.

3. What causes the U0077 code to appear?

Possible causes include damaged or corroded wiring, faulty control modules, poor connections in the CAN bus network, or a failed chassis expansion module.

4. Can the U0077 code affect drivability in a 2018 GMC Sierra?

In most cases, U0077 does not directly impact drivability, but it can lead to malfunctions in systems like stability control, braking, or other chassis-related functions.

5. How can I diagnose the U0077 code on my GMC Sierra?

Start by inspecting the CAN bus wiring for damage or corrosion, checking connections at related modules, and scanning all modules for additional fault codes to pinpoint the issue.

6. What tools are needed to troubleshoot the U0077 code?

Youâ€™ll need an OBDII scanner capable of reading manufacturer-specific codes, a multimeter for testing electrical connections, and potentially a wiring diagram for the CAN bus system.

7. Can I clear the U0077 code without repairs?

Clearing the code without addressing the root cause may work temporarily, but the problem will likely return unless the underlying issue is fixed.

8. How much does it cost to fix the U0077 code on a 2018 GMC Sierra?

Repair costs vary depending on the issue, ranging from $50 for simple wiring repairs to $500 or more for replacing a faulty control module.

9. Is the U0077 code a common issue in 2018 GMC Sierra trucks?

While not extremely common, communication errors like U0077 can occur due to wear, environmental factors, or manufacturing defects in the electrical system.

10. Can I drive my GMC Sierra with the U0077 code present?

You may be able to drive the vehicle, but it's important to address the issue promptly as it could lead to further system malfunctions or safety concerns.