AutoCodes – GMC – U0020 GMC

U0020 GMC 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 GMC 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 3,212

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

What does this mean?

What are the Possible Causes of the DTC U0020 GMC?

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 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 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 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.

Need more information about the U0020 GMC code?

Need more information on how to fix the U0020 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0020 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

U0020 2014 GMC Sierra — Low Speed CAN Bus
U0020 2015 GMC Sierra — Low Speed CAN Bus
U0020 2016 GMC Sierra — Low Speed CAN Bus
U0020 2017 GMC Sierra — Low Speed CAN Bus
U0020 2018 GMC Sierra — Low Speed CAN 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 U0020 GMC Code

1. What are the common symptoms of OBDII code U0020 in a GMC related to the Low Speed CAN Bus?

- Common symptoms include issues with the vehicle's instrument cluster, erratic behavior of electronic components, and communication failures between modules.

2. What are the possible causes of OBDII code U0020 in a GMC related to the Low Speed CAN Bus?

- Possible causes include damaged wiring or connectors in the CAN bus system, faulty control modules, software issues, and electrical problems.

3. How can I diagnose the source of OBDII code U0020 in a GMC related to the Low Speed CAN Bus?

- Diagnosis involves using a scan tool to check for other related trouble codes, inspecting the wiring and connectors for damage, and testing the communication between modules.

4. Is it safe to drive with OBDII code U0020 related to the Low Speed CAN Bus in a GMC?

- It is not recommended to drive with this code present, as it can lead to potential safety hazards due to communication issues between critical vehicle systems.

5. Can I repair OBDII code U0020 related to the Low Speed CAN Bus in a GMC myself?

- While some basic troubleshooting steps can be taken, diagnosing and repairing this code may require advanced knowledge and specialized equipment, so it is recommended to seek professional help.

6. Are there any common fixes for OBDII code U0020 related to the Low Speed CAN Bus in a GMC?

- Common fixes include repairing damaged wiring or connectors, updating control module software, and replacing faulty modules as needed.

7. How much does it typically cost to repair OBDII code U0020 related to the Low Speed CAN Bus in a GMC?

- Repair costs can vary depending on the underlying issue, but they may range from a few hundred to over a thousand dollars, including parts and labor.

8. Can resetting the OBDII code U0020 related to the Low Speed CAN Bus in a GMC resolve the issue?

- Resetting the code may temporarily clear the warning light, but if the underlying problem is not addressed, the code is likely to reappear.

9. What other OBDII codes may be related to or triggered by U0020 in a GMC related to the Low Speed CAN Bus?

- Other related codes may include U0021, U0022, U0023, and U0024, which indicate different communication issues within the CAN bus system.

10. How can I prevent OBDII code U0020 related to the Low Speed CAN Bus in a GMC from occurring in the future?

- Regular maintenance, avoiding electrical system modifications, and promptly addressing any warning signs can help prevent this code from reoccurring.