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Engine-Codes – Generic – U1838

U1838 Code - Lost Communication With Battery Charger Control Module On High Voltage Energy Management CAN Bus

Quick Answer

The U1838 code indicates that the vehicle has lost communication with the Battery Charger Control Module on the High Voltage Energy Management CAN Bus. Common causes include Faulty Wiring: Damaged or corroded wiring can disrupt communication between the modules in the high voltage system, Malfunctioning Battery Charger Control Module: A faulty Battery Charger Control Module can prevent proper communication with the vehicle's onboard computer, High Voltage Energy Management CAN Bus Issues: Problems with the CAN Bus network can lead to communication errors between modules. 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
U1838 indicates Lost Communication With Battery Charger Control Module On High Voltage Energy Management CAN Bus.
Common causes
Common causes include Faulty Wiring: Damaged or corroded wiring can disrupt communication between the modules in the high voltage system, Malfunctioning Battery Charger Control Module: A faulty Battery Charger Control Module can prevent proper communication with the vehicle's onboard computer, High Voltage Energy Management CAN Bus Issues: Problems with the CAN Bus network can lead to communication errors between modules.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 11, 2024
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Code U1838 Description

The U1838 code indicates that the vehicle has lost communication with the Battery Charger Control Module on the High Voltage Energy Management CAN Bus. In hybrid or electric vehicles, the Battery Charger Control Module is responsible for managing the charging process of the high voltage battery. The High Voltage Energy Management CAN Bus is a communication network that allows various modules in the vehicle to exchange data related to the high voltage system.

OBDII Code U1838 - Lost Communication With Battery Charger Control Module On High Voltage Energy Management CAN Bus
U1838 Code - Lost Communication With Battery Charger Control Module On High Voltage Energy Management CAN Bus

Common Causes of U1838

  1. Faulty Wiring: Damaged or corroded wiring can disrupt communication between the modules in the high voltage system.
  2. Malfunctioning Battery Charger Control Module: A faulty Battery Charger Control Module can prevent proper communication with the vehicle's onboard computer.
  3. High Voltage Energy Management CAN Bus Issues: Problems with the CAN Bus network can lead to communication errors between modules.
  4. Faulty Connectors: Loose or damaged connectors can interfere with the transmission of data between components in the high voltage system.
  5. Software Malfunction: An issue with the vehicle's onboard computer software can also cause communication errors with the Battery Charger Control Module.

Symptoms of U1838

  1. Check Engine Light: The most common symptom associated with the U1838 code is the illumination of the Check Engine Light on the vehicle's dashboard.
  2. Inability to Charge: The vehicle may have difficulty charging the high voltage battery or may not charge at all.
  3. Reduced Fuel Efficiency: The vehicle may experience decreased fuel efficiency due to improper charging of the high voltage battery.
  4. Power Loss: The vehicle may exhibit a loss of power or acceleration due to issues with the high voltage system.
  5. Erratic Behavior: The vehicle may exhibit erratic behavior or performance due to communication issues with the Battery Charger Control Module.

How to Fix U1838

  1. Diagnose the Issue: Use a diagnostic scanner to retrieve the trouble codes and pinpoint the source of the communication loss.
  2. Inspect Wiring and Connectors: Check the wiring harness and connectors for any signs of damage or corrosion. Repair or replace as needed.
  3. Test Battery Charger Control Module: Verify the functionality of the Battery Charger Control Module and replace if faulty.
  4. Check High Voltage Energy Management CAN Bus: Inspect the CAN Bus network for any faults or issues and address accordingly.
  5. Clear Codes and Test Drive: Clear the trouble codes from the vehicle's computer system and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix U1838

The cost of repairing a U1838 code can vary depending on the specific cause of the issue and the make and model of the vehicle. On average, the repair costs for this issue can range from $200 to $600, including parts and labor. However, it is important to note that diagnostic time and labor rates at auto repair shops can vary, with rates typically ranging between $80 and $150 per hour. Rates may be higher at dealerships or in metropolitan areas, while independent shops may offer lower rates. It is recommended to check with local repair shops for a more precise estimate based on your specific vehicle and location.

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Code U1838 Information for Specific Makes

  • U1838 Buick — Lost Communication With Battery Charger Control Module On High Voltage Energy Management CAN Bus
  • U1838 Cadillac — Lost Communication With Battery Charger Control Module On High Voltage Energy Management CAN Bus
  • U1838 Chevrolet — Lost Communication With Battery Charger Control Module On High Voltage Energy Management CAN Bus
  • U1838 GMC — Lost Communication With Battery Charger Control 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 U1838 Code

1. What are common symptoms of OBDII code U1838?

- Common symptoms include the inability to charge the high voltage battery, the vehicle not starting or running properly, and warning lights related to the high voltage energy management system.

2. What can cause OBDII code U1838 to occur?

- This code is typically triggered when there is a communication failure between the battery charger control module and the high voltage energy management CAN bus. Possible causes include wiring issues, a faulty battery charger control module, or problems with the CAN bus network.

3. How can I diagnose the root cause of OBDII code U1838?

- To diagnose the issue, it is recommended to perform a thorough inspection of the wiring harness connecting the battery charger control module to the CAN bus network. Additionally, using a diagnostic scanner to check for any other related trouble codes can help pinpoint the problem.

4. Is it safe to continue driving with OBDII code U1838 present?

- It is not recommended to drive the vehicle with this code present, as it may lead to further issues with the high voltage energy management system. It is best to address the problem promptly to ensure the vehicle's safety and performance.

5. Can I repair OBDII code U1838 myself?

- Repairing this code may require advanced diagnostic tools and knowledge of high voltage systems. It is recommended to seek assistance from a qualified technician or a dealership specializing in hybrid or electric vehicles to properly diagnose and repair the issue.

6. How much does it typically cost to repair OBDII code U1838?

- The cost of repairing this code can vary depending on the root cause of the issue. It may range from a few hundred to a few thousand dollars, considering the cost of parts and labor involved in diagnosing and fixing the problem.

7. Are there any preventive measures to avoid OBDII code U1838 in the future?

- Regular maintenance of the high voltage energy management system, including checking the wiring connections and keeping the components clean, can help prevent issues that may lead to this code. Additionally, following the manufacturer's recommended service schedule is crucial.

8. Can a low or dead high voltage battery cause OBDII code U1838 to appear?

- Yes, a low or dead high voltage battery can potentially trigger this code due to the communication failure between the battery charger control module and the high voltage energy management system. Ensuring the high voltage battery is properly charged is essential in avoiding this issue.

9. How long does it take to repair OBDII code U1838?

- The repair time for this code can vary depending on the exact cause of the problem and the availability of parts. It may take a few hours to a full day to diagnose and repair the issue, so it's advisable to plan accordingly.

10. Will resetting the OBDII code U1838 fix the problem permanently?

- Simply resetting the code may temporarily clear the warning light, but it will not fix the underlying issue causing the communication failure. It is crucial to address the root cause of the problem to prevent the code from reappearing in the future.

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