AutoCodes – Generic – U18A4

U18A4 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 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.

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Code Popularity 1,794

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

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?

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 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 code?

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

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Information for Specific Makes

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

1. What are common symptoms of OBDII code U18A4?

- Common symptoms include hybrid/EV battery charging issues, warning lights on the dashboard, and limited vehicle power.

2. What can cause the OBDII code U18A4 to be triggered?

- This code is usually triggered by a communication breakdown between the hybrid/EV battery DC charging communications gateway module and the high voltage energy management CAN bus.

3. How can I diagnose the cause of OBDII code U18A4?

- Diagnosing this code typically involves checking the wiring connections, inspecting the gateway module, and using a diagnostic scan tool to identify communication errors.

4. Is it safe to continue driving with the OBDII code U18A4 present?

- It is not recommended to continue driving with this code active, as it can lead to further damage to the hybrid/EV system and potentially affect the vehicle's performance.

5. What are some repair tips for fixing OBDII code U18A4?

- Repair tips may include checking and repairing any damaged wiring, replacing the faulty gateway module, resetting the system, and clearing the trouble codes.

6. Can a DIY enthusiast fix the OBDII code U18A4 at home?

- While some basic troubleshooting steps can be done at home, fixing this code may require specialized tools and expertise, so it is recommended to consult a professional mechanic.

7. How much does it typically cost to repair OBDII code U18A4?

- The cost of repairing this code can vary depending on the underlying issue, but it may range from a few hundred to a couple of thousand dollars, including parts and labor.

8. Will resetting the OBDII code U18A4 make it go away permanently?

- Resetting the code may temporarily clear the warning light, but if the underlying issue is not resolved, the code is likely to reappear once the system detects the problem again.

9. Can extreme weather conditions impact the occurrence of OBDII code U18A4?

- Extreme weather conditions, such as high temperatures or humidity, can potentially affect the performance of the hybrid/EV battery system and contribute to communication errors triggering this code.

10. Are there any recalls or technical service bulletins related to OBDII code U18A4?

- It is advisable to check with the vehicle manufacturer or authorized dealerships for any recalls or technical service bulletins related to this specific OBDII code to stay informed about potential resolutions or updates.