AutoCodes – GMC – U18B3 GMC

U18B3 GMC Code - Lost Communications With Navigation Control Module On Ethernet Bus

Quick Answer

At the core of the infotainment system is the Radio Ethernet Audio Video Bridging switch which communicates directly to each contributing Infotainment control module terminator. Common causes include Faulty Navigation Control Module, Navigation Control Module harness is open or shorted, Navigation 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: U18B3 GMC indicates Lost Communications With Navigation Control Module On Ethernet Bus.
Common causes: Common causes include Faulty Navigation Control Module, Navigation Control Module harness is open or shorted, Navigation 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 447

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 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U18B3 GMC Description

At the core of the infotainment system is the Radio Ethernet Audio Video Bridging switch which communicates directly to each contributing Infotainment control module terminator. The Ethernet harness consists of twisted pair wires from point to point. Each control module on the Ethernet infotainment system sends/receives data at 100 Mbit/s to/from a specified port at the Radio. The Radio Ethernet will also be used to program USB software update files to the control modules connected to the Ethernet ports. The Diagnostic Trouble Code (DTC) will set a supervised periodic message that includes the transmitter device availability that has not been received.

OBDII Code U18B3 GMC - Lost Communications With Navigation Control Module On Ethernet Bus - AutoCodes.com — U18B3 GMC Code - Lost Communications With Navigation Control Module On Ethernet Bus

What does this mean?

What are the Possible Causes of the DTC U18B3 GMC?

Faulty Navigation Control Module
Navigation Control Module harness is open or shorted
Navigation Control Module circuit poor electrical connection

How to Fix the DTC U18B3 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 U18B3 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 U18B3 GMC code?

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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 U18B3 GMC Code

What does the OBDII code U18B3 mean on a GMC?

The U18B3 code indicates a loss of communication with the Navigation Control Module over the Ethernet bus, signaling potential network or module issues.

What are the common symptoms of the U18B3 code in a GMC vehicle?

Symptoms may include a non-functional navigation system, blank or frozen infotainment screen, or error messages related to the navigation or connectivity system.

What causes the U18B3 code to appear in a GMC?

Common causes include a faulty Navigation Control Module, damaged wiring or connectors in the Ethernet bus, software glitches, or an issue with the vehicle's communication network.

Can driving with the U18B3 code cause further damage?

While the code itself doesnâ€™t typically cause direct damage, unresolved communication issues may lead to further malfunctions in the infotainment or vehicle systems.

How do you diagnose the U18B3 code on a GMC vehicle?

Diagnosis involves scanning for related codes, inspecting Ethernet bus wiring and connectors, checking for software updates, and testing the Navigation Control Module for functionality.

What repairs are commonly needed to fix the U18B3 code?

Repairs may include replacing or reprogramming the Navigation Control Module, repairing damaged wiring or connectors, or updating the infotainment system software.

Can a software update fix the U18B3 code?

Yes, if the issue is caused by a software glitch, updating the vehicleâ€™s infotainment or navigation system software may resolve the code.

How much does it cost to repair the U18B3 code on a GMC?

The cost can vary widely depending on the exact issue but may range from $100 for a reprogramming to $1,000 or more for module replacement.

Can I fix the U18B3 code myself?

If youâ€™re experienced with automotive systems, you might inspect wiring or update software, but module replacements and advanced diagnostics typically require professional tools and expertise.

What tools are needed to troubleshoot the U18B3 code?

Youâ€™ll need an advanced OBDII scanner capable of reading manufacturer-specific codes, a multimeter for testing wiring, and possibly a laptop with software for reprogramming modules.