AutoCodes – GMC – U0020 2018 GMC Sierra

U0020 2018 GMC Sierra Code - Low Speed CAN Bus

Quick Answer

Devices connected to the General Motors Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include If other codes are present, diagnose other codes first, 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: U0020 2018 GMC Sierra indicates Low Speed CAN Bus.
Common causes: Common causes include If other codes are present, diagnose other codes first, 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 224

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
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U0020 2018 GMC Sierra Description

Devices connected to the General Motors 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. The devices have programmed information about what messages need to be exchanged on the serial data circuits. The messages are also supervised, and some periodic messages are used by the receiver device as an availability indication of the transmitter device. The Diagnostic Trouble Code (DTC) will be set when a supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U0020 2018 GMC Sierra - Low Speed CAN Bus - AutoCodes.com — U0020 2018 GMC Sierra Code - Low Speed CAN Bus

What does this mean?

What are the Possible Causes of the DTC U0020 2018 GMC Sierra?

If other codes are present, diagnose other codes first
Faulty Control Module
Control Module harness is open or shorted
Control Module circuit poor electrical connection

How to Fix the DTC U0020 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 does this mean?

Code Tech Notes

Controller Area Network (CAN)

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0020 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 U0020 2018 GMC Sierra code?

Need more information on how to fix the U0020 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 U0020 2018 GMC Sierra Code

What does the OBDII code U0020 mean for a 2018 GMC Sierra?

The OBDII code U0020 indicates a problem with the Low Speed CAN Bus communication, which is responsible for data exchange between various modules in the vehicle.

What symptoms might I experience if my GMC Sierra has the U0020 code?

Common symptoms include warning lights on the dashboard, erratic behavior of electronic components, and communication failures between modules.

What are some common causes of the U0020 code in a 2018 GMC Sierra?

Possible causes include a faulty CAN bus wiring harness, damaged connectors, a malfunctioning control module, or issues with the vehicle's battery or ground connections.

How can I diagnose the U0020 code in my GMC Sierra?

Start by visually inspecting the wiring and connectors for damage. Use a scan tool to check for other related codes and monitor the CAN bus communication while running tests.

What repairs might be needed to fix the U0020 code?

Repairs may involve repairing or replacing damaged wiring or connectors, reprogramming or replacing control modules, or fixing grounding issues within the electrical system.

Can I drive my GMC Sierra with the U0020 code?

While you can drive the vehicle, it is not recommended due to the potential for electronic component malfunctions and safety concerns.

Is the U0020 code a serious issue?

Yes, a U0020 code can indicate significant communication issues within the vehicle's network, which can lead to more extensive problems if not addressed promptly.

Are there any specific tools required to troubleshoot the U0020 code?

A good OBDII scanner that can read manufacturer-specific codes and a multimeter for checking electrical connections are essential tools for diagnosing this issue.

How much does it typically cost to repair the U0020 code?

Repair costs can vary widely depending on the specific issue, but they generally range from $100 to $1,000 or more, depending on whether it involves simple wiring fixes or module replacements.