AutoCodes – GMC – U18A4 GMC

U18A4 GMC 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 GMC 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 610

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

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 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 U18A4 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 U18A4 GMC code?

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Need Help with the 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 U18A4 GMC Code

1. What are common symptoms of OBDII code U18A4 GMC?

- Common symptoms include a check engine light, loss of communication with the hybrid/EV battery DC charging system, and potential issues with high voltage energy management.

2. What can cause the OBDII code U18A4 GMC to trigger?

- The code can be triggered by a fault in the communications gateway module on the high voltage energy management CAN bus, leading to a loss of communication with the hybrid/EV battery DC charging system.

3. How serious is the U18A4 GMC code?

- The code is considered serious as it involves a loss of communication with crucial components related to the hybrid/EV battery system, which can affect the vehicle's performance and efficiency.

4. What should I do if I encounter the U18A4 GMC code?

- It is recommended to have the vehicle diagnosed by a qualified technician to determine the exact cause of the communication loss and to address any underlying issues promptly.

5. Can I continue driving with the U18A4 GMC code present?

- It is not advisable to continue driving with the code present, as it can lead to potential issues with the hybrid/EV battery system and high voltage energy management.

6. How can the U18A4 GMC code be repaired?

- Repairing the U18A4 GMC code typically involves diagnosing and fixing the underlying communication issue with the hybrid/EV battery DC charging communications gateway module on the high voltage energy management CAN bus.

7. Are there any DIY tips for addressing the U18A4 GMC code?

- Due to the complexity of the hybrid/EV system involved, it is recommended to seek professional help for diagnosing and repairing the U18A4 GMC code to ensure proper handling of high voltage components.

8. Can a faulty battery be the cause of the U18A4 GMC code?

- While a faulty battery can potentially cause communication issues in the hybrid/EV system, the U18A4 GMC code specifically points to problems with the communications gateway module and high voltage energy management CAN bus.

9. Is the U18A4 GMC code specific to GMC vehicles only?

- The U18A4 code may be specific to GMC vehicles, but the underlying issue of lost communication with the hybrid/EV battery DC charging system can be present in other hybrid or electric vehicles as well.

10. How can I prevent the U18A4 GMC code from recurring?

- Regular maintenance and inspection of the hybrid/EV system, including the communications gateway module and high voltage energy management CAN bus, can help prevent the recurrence of the U18A4 GMC code.