AutoCodes – GMC – U18B9 GMC

U18B9 GMC 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 GMC 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 735

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 Aug 09, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U18B9 GMC 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 GMC - Primary High Speed CAN Bus Subnet Configuration List - AutoCodes.com — U18B9 GMC Code - Primary High Speed CAN Bus Subnet Configuration List

What does this mean?

What are the Possible Causes of the DTC U18B9 GMC?

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

How to Fix the DTC U18B9 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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U18B9 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 U18B9 GMC code?

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

Need Help with the Code?

Get the U18B9 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

U18B9 2014 GMC Sierra — Primary High Speed CAN Bus Subnet Configuration List
U18B9 2015 GMC Sierra — Primary High Speed CAN Bus Subnet Configuration List
U18B9 2016 GMC Sierra — Primary High Speed CAN Bus Subnet Configuration List
U18B9 2017 GMC Sierra — Primary High Speed CAN Bus Subnet Configuration List
U18B9 2018 GMC Sierra — Primary High Speed CAN Bus Subnet Configuration List

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 GMC Code

1. What does the OBDII code U18B9 GMC indicate?

The U18B9 code for GMC refers to "Primary High Speed CAN Bus Subnet Configuration List" communication error.

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

Common symptoms include intermittent or complete loss of communication between various control modules in the vehicle, leading to issues with functionality and diagnostics.

3. What are the possible causes of the U18B9 code in a GMC vehicle?

Potential causes include faulty wiring or connections in the CAN bus network, damaged control modules, software glitches, or issues with the diagnostic tools being used.

4. How do I diagnose the U18B9 code in my GMC vehicle?

Diagnosis involves checking the wiring and connections in the CAN bus network, inspecting control modules for damage, updating software as needed, and using diagnostic tools to pinpoint the communication error.

5. Can I still drive my GMC vehicle with the U18B9 code present?

It is not recommended to drive the vehicle with the U18B9 code active, as it can lead to further communication failures and potential safety hazards.

6. How can I repair the U18B9 code in my GMC vehicle?

Repair methods may include repairing or replacing damaged wiring, addressing faulty control modules, updating software, and resetting the diagnostic trouble codes.

7. Is the U18B9 code a common issue in GMC vehicles?

The U18B9 code related to CAN bus communication errors can occur in various GMC models, especially in vehicles with complex electronic systems.

8. Can a DIY enthusiast fix the U18B9 code issue in a GMC vehicle?

While some basic diagnosis and repairs can be attempted by DIY enthusiasts, addressing complex CAN bus communication errors may require professional expertise and specialized tools.

9. How much does it cost to repair the U18B9 code in a GMC vehicle?

The cost of repairing the U18B9 code can vary depending on the underlying cause, the extent of the issue, and whether professional assistance is required. Costs may include parts, labor, and diagnostic fees.

10. How can I prevent the U18B9 code from recurring in my GMC vehicle?

Regular maintenance, keeping the vehicle's software up to date, and addressing any wiring or connection issues promptly can help prevent the U18B9 code from reoccurring in a GMC vehicle.