AutoCodes – Generic – U18A3

U18A3 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 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 524

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

What does this mean?

What are the Possible Causes of the DTC U18A3?

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?

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 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 code?

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Information for Specific Makes

U18A3 Buick — Lost Communication With Human Machine Interface Control Module
U18A3 Cadillac — Lost Communication With Human Machine Interface Control Module
U18A3 Chevrolet — Lost Communication With Human Machine Interface Control Module
U18A3 GMC — Lost Communication With Human Machine Interface Control Module

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 Code

1. What are common symptoms of the OBDII code U18A3 (Lost Communication With Human Machine Interface Control Module)?

- Common symptoms include loss of functionality of certain vehicle controls or displays, such as touchscreen, buttons, or infotainment system.

2. What can cause the U18A3 code to appear?

- The U18A3 code may appear due to a faulty Human Machine Interface (HMI) control module, damaged wiring or connectors, or software issues.

3. How can I diagnose the cause of the U18A3 code?

- Diagnosis typically involves checking the wiring and connectors leading to the HMI module, testing the module itself for functionality, and verifying software updates or reprogramming.

4. Can a DIYer repair the U18A3 code issue?

- Repairing the U18A3 code may require advanced diagnostic tools and expertise, making it challenging for a DIYer. Professional help may be necessary.

5. Is it safe to continue driving with the U18A3 code present?

- It is not recommended to drive with the U18A3 code present, as it can affect important vehicle controls and systems, compromising safety and functionality.

6. How much does it typically cost to repair the U18A3 code issue?

- The cost of repairing the U18A3 code can vary depending on the underlying cause, but it may involve replacing the HMI module, repairing wiring, or addressing software issues, potentially ranging from a few hundred to over a thousand dollars.

7. Can resetting the OBDII code U18A3 resolve the issue temporarily?

- Resetting the code may temporarily clear the warning light, but if the underlying cause is not addressed, the issue is likely to reappear.

8. Are there any preventative maintenance tips to avoid the U18A3 code?

- Regularly inspecting and maintaining the vehicle's electrical system, including wiring and connectors, can help prevent issues like the U18A3 code from occurring.

9. How long does it take to repair the U18A3 code issue?

- The repair time for the U18A3 code can vary depending on the specific cause and complexity of the repair, ranging from a few hours to a full day or more in some cases.

10. Can the U18A3 code be intermittent in nature?

- Yes, the U18A3 code can sometimes be intermittent, with the communication loss between the HMI module and other systems occurring sporadically, making diagnosis and repair more challenging.