AutoCodes – GMC – U18B9 2018 GMC Sierra

U18B9 2018 GMC Sierra Code - Primary High Speed CAN Bus Subnet Configuration List

Quick Answer

The devices on the high-speed General Motor Local Area Network (GMLAN) serial data bus and the chassis high-speed GMLAN serial data bus must be programmed with software that specifically identifies the correct type and quantity of devices on the bus based on RPO configuration. Common causes include Faulty Module that is not configured, Module harness is open or shorted, Module circuit poor electrical connection. 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: U18B9 2018 GMC Sierra indicates Primary High Speed CAN Bus Subnet Configuration List.
Common causes: Common causes include Faulty Module that is not configured, Module harness is open or shorted, Module circuit poor electrical connection.
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 178

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 24, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U18B9 2018 GMC Sierra Description

The devices on the high-speed General Motor Local Area Network (GMLAN) serial data bus and the chassis high-speed GMLAN serial data bus must be programmed with software that specifically identifies the correct type and quantity of devices on the bus based on RPO configuration. If a device was not properly configured after installation, the appropriate U Code may be set for that device. No external circuit diagnosis is involved. The Diagnostic Trouble Code (DTC) will set when the device is not configured properly, or the device recognizes a programming error.

OBDII Code U18B9 2018 GMC Sierra - Primary High Speed CAN Bus Subnet Configuration List - AutoCodes.com — U18B9 2018 GMC Sierra Code - Primary High Speed CAN Bus Subnet Configuration List

What does this mean?

What are the Possible Causes of the DTC U18B9 2018 GMC Sierra?

Faulty Module that is not configured
Module harness is open or shorted
Module circuit poor electrical connection

How to Fix the DTC U18B9 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 U18B9 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 U18B9 2018 GMC Sierra code?

Need more information on how to fix the U18B9 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U18B9 2018 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 U18B9 2018 GMC Sierra Code

1. What does the OBDII code U18B9 mean for a 2018 GMC Sierra?

The U18B9 code indicates an issue with the Primary High Speed CAN Bus Subnet Configuration List in the vehicle's communication network.

2. What are the common symptoms of a U18B9 code in a 2018 GMC Sierra?

Common symptoms may include erratic behavior of electronic components, dashboard warning lights, communication failures between control modules, and potentially issues with vehicle performance.

3. What are some possible causes of the U18B9 code in a 2018 GMC Sierra?

Possible causes of the U18B9 code can include damaged wiring or connectors in the CAN bus network, faulty control modules, software glitches, or a malfunctioning CAN bus gateway module.

4. How can I diagnose the U18B9 code in my 2018 GMC Sierra?

Diagnosing the U18B9 code typically involves using an OBDII scanner to retrieve the code and then conducting a thorough inspection of the CAN bus network components, checking for any visible damage or loose connections.

5. What are some repair tips for fixing the U18B9 code in a 2018 GMC Sierra?

Repairing the U18B9 code may involve repairing or replacing damaged wiring, connectors, or control modules in the CAN bus network, updating software if necessary, and ensuring all components are properly connected and functioning.

6. Can I drive my 2018 GMC Sierra with a U18B9 trouble code?

It is not recommended to drive the vehicle with an unresolved U18B9 code, as it may lead to further communication issues between critical systems in the vehicle.

7. How much does it cost to repair the U18B9 code in a 2018 GMC Sierra?

The cost of repairing a U18B9 code can vary depending on the extent of the issue, the parts needed for repair, and the labor rates of the repair shop. It's recommended to obtain a few quotes from different service centers.

8. Can a DIY enthusiast fix the U18B9 code in a 2018 GMC Sierra?

While some basic troubleshooting steps can be performed by a DIY enthusiast, diagnosing and repairing the U18B9 code may require specialized tools and expertise, so it's best to consult with a professional technician.

9. Will resetting the trouble codes make the U18B9 code disappear in my 2018 GMC Sierra?

Resetting the trouble codes may temporarily clear the U18B9 code, but if the underlying issue is not addressed, the code is likely to reappear once the vehicle's systems detect the problem again.

10. How long does it take to repair the U18B9 code in a 2018 GMC Sierra?

The repair time for a U18B9 code can vary depending on the exact cause of the issue and the complexity of the repair. It's best to consult with a mechanic for an accurate estimate of the repair duration.