AutoCodes – GMC – U18A3 GMC

U18A3 GMC Code - Lost Communication With Human Machine Interface Control Module

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Human Machine Interface Control Module, Human Machine Interface Control Module harness is open or shorted, Human Machine Interface 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: U18A3 GMC indicates Lost Communication With Human Machine Interface Control Module.
Common causes: Common causes include Faulty Human Machine Interface Control Module, Human Machine Interface Control Module harness is open or shorted, Human Machine Interface 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 624

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 U18A3 GMC 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 U18A3 GMC - Lost Communication With Human Machine Interface Control Module - AutoCodes.com — U18A3 GMC Code - Lost Communication With Human Machine Interface Control Module

What does this mean?

What are the Possible Causes of the DTC U18A3 GMC?

Faulty Human Machine Interface Control Module
Human Machine Interface Control Module harness is open or shorted
Human Machine Interface Control Module circuit poor electrical connection

How to Fix the DTC U18A3 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 U18A3 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 U18A3 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 U18A3 GMC Code

1. What are the common symptoms of OBDII code U18A3 GMC?

Symptoms may include issues with the vehicle's infotainment system, malfunctioning touch screen, unresponsive controls, and loss of communication with the human machine interface control module.

2. What are the possible causes of the U18A3 GMC trouble code?

Potential causes include a faulty human machine interface control module, wiring issues, loose connections, software glitches, or a malfunction in the infotainment system.

3. How can I diagnose the U18A3 GMC code?

Diagnosis typically involves using a professional OBDII scanner to retrieve the code, inspecting the wiring and connections related to the human machine interface control module, and checking for any software updates or recalls from the manufacturer.

4. Can I still drive my vehicle with the U18A3 trouble code?

It is generally safe to drive the vehicle with this code, but it is recommended to address the issue promptly to avoid potential inconvenience or further complications with the infotainment system.

5. How can I repair the U18A3 GMC code?

Repair methods may include resetting the infotainment system, checking and repairing any damaged wiring or connections, updating the software, or replacing the human machine interface control module if necessary.

6. Is the U18A3 GMC code a common issue in certain GMC models?

This code is more commonly reported in specific GMC models known for infotainment system issues, such as the GMC Acadia, Terrain, and Yukon.

7. Can a DIY enthusiast fix the U18A3 trouble code at home?

Depending on the root cause, some DIY enthusiasts may be able to address the issue by checking connections and wiring, performing software updates, or resetting the infotainment system. However, more complex repairs may require professional assistance.

8. Will resetting the trouble code make it go away permanently?

Resetting the trouble code may temporarily clear the warning, but if the underlying issue causing the U18A3 code is not resolved, the code is likely to reappear upon further diagnostics or system checks.

9. How long does it typically take to repair the U18A3 GMC trouble code?

The repair time can vary depending on the cause of the code and the complexity of the fix. Simple solutions like software updates may take a short time, while replacing components or addressing wiring issues could require more extensive labor.

10. Are there any recalls or service bulletins related to the U18A3 trouble code?

It is recommended to check with the manufacturer or authorized service centers for any recalls or service bulletins related to the U18A3 code, as certain issues may be covered under warranty or special campaigns.