AutoCodes – Generic – U18B9

U18B9 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 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 1,857

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 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 - Primary High Speed CAN Bus Subnet Configuration List - AutoCodes.com — U18B9 Code - Primary High Speed CAN Bus Subnet Configuration List

What does this mean?

What are the Possible Causes of the DTC U18B9?

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

How to Fix the DTC U18B9?

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 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 code?

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

Need Help with the Code?

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

Information for Specific Makes

U18B9 Buick — Primary High Speed CAN Bus Subnet Configuration List
U18B9 Cadillac — Primary High Speed CAN Bus Subnet Configuration List
U18B9 Chevrolet — Primary High Speed CAN Bus Subnet Configuration List
U18B9 GMC — 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 Code

1. What does OBDII code U18B9 mean?

Code U18B9 indicates an issue with the Primary High Speed CAN Bus Subnet Configuration List in the vehicle's onboard diagnostics system.

2. What are common symptoms of OBDII code U18B9?

Common symptoms of code U18B9 may include communication errors with various control modules, warning lights illuminated on the dashboard, and issues with vehicle performance.

3. What are possible causes of OBDII code U18B9?

Possible causes of code U18B9 can include wiring or connection problems in the CAN bus network, faults in control modules, software issues, or a faulty CAN bus gateway module.

4. How can I diagnose OBDII code U18B9?

Diagnosing code U18B9 typically involves using a professional diagnostic scanner to scan for fault codes, checking the CAN bus connections for any issues, and performing pinpoint tests as recommended by the vehicle manufacturer.

5. Can OBDII code U18B9 be repaired at home?

Repairing OBDII code U18B9 may require advanced diagnostic equipment and expertise, so it is recommended to seek assistance from a qualified mechanic or dealership to properly diagnose and repair the issue.

6. Is it safe to drive with OBDII code U18B9 active?

If code U18B9 is present, it is advisable to address the underlying issue as soon as possible to prevent potential further damage to the vehicle's systems and ensure safe operation.

7. How much does it cost to fix OBDII code U18B9?

The cost of repairing code U18B9 can vary depending on the underlying cause of the issue, the extent of diagnostics required, and the labor rates of the repair facility.

8. Can resetting the fault codes clear OBDII code U18B9?

Resetting the fault codes may temporarily clear the code U18B9, but if the underlying issue is not addressed, the code is likely to reappear once the vehicle is driven and the diagnostic system runs its checks again.

9. Are there any recalls related to OBDII code U18B9?

Recalls related to code U18B9 can vary by vehicle make and model, so it is advisable to check with the manufacturer or a dealership to see if there are any relevant recalls that may apply to your vehicle.

10. How can I prevent OBDII code U18B9 from occurring again?

To help prevent code U18B9 from occurring again, it is important to perform regular maintenance on the vehicle, address any wiring or connection issues promptly, and follow the manufacturer's recommendations for software updates and inspections.