AutoCodes – Generic – U18B8

U18B8 Code - Lost Communication With Body Control Module On High Speed CAN Bus

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Body Control Module (BCM), Body Control Module harness is open or shorted, Body Control 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: U18B8 indicates Lost Communication With Body Control Module On High Speed CAN Bus.
Common causes: Common causes include Faulty Body Control Module (BCM), Body Control Module harness is open or shorted, Body Control 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 513

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 Jun 09, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U18B8 Description

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device. The Diagnostic Trouble Code (DTC) will set a supervised periodic message that includes the transmitter device availability that has not been received.

OBDII Code U18B8 - Lost Communication With Body Control Module On High Speed CAN Bus - AutoCodes.com — U18B8 Code - Lost Communication With Body Control Module On High Speed CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18B8?

Faulty Body Control Module (BCM)
Body Control Module harness is open or shorted
Body Control Module circuit poor electrical connection

How to Fix the DTC U18B8?

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 U18B8 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 U18B8 code?

Need more information on how to fix the U18B8 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U18B8 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U18B8 Buick — Lost Communication With Body Control Module On High Speed CAN Bus
U18B8 Cadillac — Lost Communication With Body Control Module On High Speed CAN Bus
U18B8 Chevrolet — Lost Communication With Body Control Module On High Speed CAN Bus
U18B8 GMC — Lost Communication With Body Control Module On High 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 U18B8 Code

1. What are the common symptoms of OBDII code U18B8?

- Common symptoms include issues with power windows, door locks, interior lights, and other body control module functions.

2. What does the OBDII code U18B8 indicate?

- The code U18B8 indicates a lost communication error between the vehicle's main computer and the body control module over the high-speed CAN bus.

3. What are the possible causes of U18B8 code?

- Possible causes include a faulty body control module, wiring or connection issues, a problem with the CAN bus network, or a malfunction in the main engine control module.

4. How can I diagnose the U18B8 code?

- Diagnosing the U18B8 code usually involves using a professional OBDII scanner to read the code and check for any additional codes related to the communication error. It may also require testing the CAN bus network and checking the body control module for proper functioning.

5. How can I repair the U18B8 code?

- Repairing the U18B8 code often involves fixing any wiring or connection issues, replacing a faulty body control module, or addressing problems with the CAN bus network. Sometimes, reprogramming or updating the software in the modules may also be necessary.

6. Can I continue driving with the U18B8 code present?

- It is not recommended to continue driving with the U18B8 code present, as it can lead to further electrical issues and potential safety hazards due to the loss of communication with the body control module.

7. Is it possible to reset the U18B8 code without repairs?

- While clearing the code temporarily may be possible, it is essential to diagnose and address the root cause of the communication error to prevent the code from reappearing.

8. How much does it cost to repair the U18B8 code?

- The cost of repairing the U18B8 code can vary depending on the specific cause of the issue, the extent of repairs needed, and whether professional diagnostic services are required. Costs may include parts, labor, and any programming or reprogramming necessary.

9. Can a DIY enthusiast fix the U18B8 code at home?

- Depending on the individual's skill level and access to tools and resources, some DIY enthusiasts may be able to address simple wiring or connection issues related to the U18B8 code. However, more complex repairs or module replacements may require professional assistance.

10. How can I prevent the U18B8 code from appearing in the future?

- Regularly checking and maintaining the vehicle's electrical system, including the CAN bus network and body control module connections, can help prevent issues that lead to the U18B8 code. Addressing any warning signs promptly can also help avoid future communication errors.