AutoCodes – Buick – U18A4 Buick

U18A4 Buick Code - Lost Communication With Hybrid/EV Battery DC Charging Communications Gateway Module On High Voltage Energy Management CAN Bus

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Hybrid/EV Battery DC Charging Communications Gateway Module, Hybrid/EV Battery DC Charging Communications Gateway Module harness is open or shorted, Hybrid/EV Battery DC Charging Communications Gateway 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: U18A4 Buick indicates Lost Communication With Hybrid/EV Battery DC Charging Communications Gateway Module On High Voltage Energy Management CAN Bus.
Common causes: Common causes include Faulty Hybrid/EV Battery DC Charging Communications Gateway Module, Hybrid/EV Battery DC Charging Communications Gateway Module harness is open or shorted, Hybrid/EV Battery DC Charging Communications Gateway 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 603

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
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code U18A4 Buick 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 U18A4 Buick - Lost Communication With Hybrid/EV Battery DC Charging Communications Gateway Module On High Voltage Energy Management CAN Bus - AutoCodes.com — U18A4 Buick Code - Lost Communication With Hybrid/EV Battery DC Charging Communications Gateway Module On High Voltage Energy Management CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18A4 Buick?

Faulty Hybrid/EV Battery DC Charging Communications Gateway Module
Hybrid/EV Battery DC Charging Communications Gateway Module harness is open or shorted
Hybrid/EV Battery DC Charging Communications Gateway Module circuit poor electrical connection

How to Fix the DTC U18A4 Buick?

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 U18A4 Buick 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 U18A4 Buick code?

Need more information on how to fix the U18A4 Buick code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U18A4 Buick code diagnosed by a professional: Find a repair shop in your area

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 U18A4 Buick Code

1. What does the OBDII code U18A4 mean for a Buick?

The U18A4 code indicates a lost communication with the hybrid/EV battery DC charging communications gateway module on the high voltage energy management CAN bus.

2. What are the common symptoms of the U18A4 code?

Symptoms may include the check engine light or service hybrid/EV system warning, reduced charging performance, or issues with the high-voltage battery system.

3. What causes the U18A4 code to appear?

Common causes include a faulty communications gateway module, wiring issues like damaged or corroded CAN bus connections, or software glitches in the vehicleâ€™s control modules.

4. Can a dead 12V battery trigger the U18A4 code?

Yes, if the 12V battery is weak or dead, it can cause communication issues on the CAN bus, potentially triggering the U18A4 code.

5. How can you diagnose the U18A4 code?

Diagnosis involves using a scan tool to check for related codes, inspecting CAN bus wiring and connectors, and testing the hybrid/EV battery DC charging communications gateway module.

6. Is the U18A4 code serious?

Yes, it can affect the vehicle's charging and high-voltage battery performance, so addressing it promptly is important to avoid further issues.

7. Can software updates fix the U18A4 code?

In some cases, a software update for the gateway module or related control units may resolve communication errors causing the U18A4 code.

8. How much does it cost to repair the U18A4 code?

Repair costs can range from $100 to $1,000 depending on whether itâ€™s a wiring repair, module replacement, or software update.

9. Can you drive with the U18A4 code?

Driving may be possible, but it's not recommended as it could lead to reduced performance or further damage to the hybrid/EV system.

10. What tools are needed to troubleshoot the U18A4 code?

Youâ€™ll need a professional-grade scan tool capable of reading CAN bus data, a multimeter for electrical testing, and wiring diagrams for the high-voltage energy management system.