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Harley Code U0140: Understanding and Fixing the Issue

by

Chase Manhattan

Chase Manhattan Avatar
Owner and Editor at The Wrench Network

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Hey y’all, it’s Chase Manhattan! I’m a life-long automotive and motorcycle enthusiast with a knack for diagnostics that I hope to share with you! Lately, I’ve been running my own motorcycle rental business, which you can read about here, and it has been a great experience that has allowed me to own numerous bikes that I probably couldn’t justify otherwise. Plus, it’s been a great way to experience new places while on vacation. If you haven’t heard of them before, I definitely recommend checking out the Riders-Share platform if you get the itch to ride while away from home, or if you want to explore a cheaper way to own and ride motorcycles!

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If you own a Harley-Davidson motorcycle, you may have encountered the U0140 code at some point. This code stands for “Lost Communication with Body Control Module (BCM)” and can cause a variety of issues with your bike. It usually means that the BCM is not properly transmitting or receiving signals from various switches and sensors in your vehicle.

There are several common causes of the U0140 code, including damaged wires, BCM internal hardware failure, and data network problems. Another possible cause is an open or shorted BCM harness. A poor electrical connection in the BCM circuit can also trigger this fault code. If you see this code on your Harley’s diagnostic display, it’s important to address the issue promptly to avoid further damage to your bike.

Fortunately, there are ways to fix the U0140 code. Depending on the cause of the issue, you may need to replace damaged wires or connectors, repair or replace the BCM, or address other electrical system faults. It’s important to work with a qualified Harley-Davidson technician to diagnose and repair the issue properly. With the right expertise and tools, you can get your Harley back on the road and running smoothly again.

Understanding Trouble Code U0140

If you’re experiencing issues with your Harley-Davidson motorcycle, one of the most common problems you might encounter is a diagnostic trouble code (DTC). One such code is U0140, which indicates that there is a problem with the communication between the vehicle’s Body Control Module (BCM) and other components.

Definition and Meaning

The U0140 code is a DTC that indicates a loss of communication between the BCM and other modules in your Harley-Davidson motorcycle. This code usually means that the BCM is not properly transmitting or receiving signals from various switches and sensors in your vehicle. The BCM is responsible for controlling various functions in your motorcycle, including the lighting, security system, and even the fuel pump.

Common Causes and Symptoms

There are several common causes of the U0140 code, including damaged wires, BCM internal hardware failure, and data network problems. A poor electrical connection in the Body Control Module circuit can also trigger this code. Some of the symptoms of a U0140 code include warning lights on the dashboard, a loss of power to certain systems, and even the inability to start your motorcycle.

If you’re experiencing any of these symptoms, it’s important to have your motorcycle diagnosed by a professional mechanic. They can use specialized equipment to read the codes and determine the root cause of the problem. In some cases, the issue may be as simple as a loose wire or a faulty sensor. In other cases, it may require more extensive repairs, such as replacing the BCM or repairing damaged wiring.

In conclusion, the U0140 code is a common issue that can affect Harley-Davidson motorcycles. If you’re experiencing any symptoms of this code, it’s important to have your motorcycle diagnosed by a professional mechanic who can determine the root cause of the problem and recommend the appropriate repairs.

Diagnosing the Issue

If you are experiencing trouble with your Harley and the U0140 code is showing up, it’s important to diagnose the issue. Here are some initial steps that you can take to identify the problem:

Initial Steps

  • Check the battery: Make sure the battery is fully charged and in good condition. A weak battery can cause communication issues between modules.
  • Check the wiring: Inspect the wiring harness for any damage or loose connections. Corroded or damaged wires can cause communication errors.
  • Check the fuses: Make sure all the fuses are in good condition and not blown. A blown fuse can cause communication issues.

If these initial steps don’t resolve the issue, you may need to use a scan tool to diagnose the problem further.

Using a Scan Tool

A scan tool is a device that connects to your Harley’s onboard computer and reads the trouble codes stored in the system. Here’s how to use a scan tool to diagnose the U0140 code:

  1. Connect the scan tool: Connect the scan tool to the diagnostic port on your Harley. The diagnostic port is usually located under the seat or on the side of the bike.
  2. Read the trouble codes: Use the scan tool to read the trouble codes stored in the system. Look for the U0140 code to identify the communication issue.
  3. Diagnose the problem: Use the scan tool to diagnose the problem further. The scan tool can help identify which module is causing the communication error.
  4. Repair or replace the module: Once you have identified the module causing the communication error, you can repair or replace it as needed.

Using a scan tool can help pinpoint the issue and save you time and money in the long run. If you are not comfortable using a scan tool or diagnosing the problem yourself, it’s best to take your Harley to a professional mechanic for assistance.

Electrical Components Inspection

When facing the U0140 code, it’s essential to inspect the electrical components of your Harley to determine the root cause of the problem. This section will guide you through the necessary steps to inspect your wiring, connectors, fuses, and relays.

Wiring and Connectors

The first step in inspecting your Harley’s electrical components is to check for any loose or damaged wiring and connectors. Loose or damaged wiring can cause a loss of communication between the body control module and other components, triggering the U0140 code.

To inspect your wiring and connectors, start by visually inspecting them for any signs of wear or damage. If you notice any damaged wiring or connectors, replace them immediately. Additionally, check that all connectors are securely plugged in and that there are no loose connections.

Fuses and Relays

The next step in inspecting your electrical components is to check your fuses and relays. Faulty fuses and relays can cause a loss of communication with the body control module, resulting in the U0140 code.

To inspect your fuses and relays, start by checking your fuse box for any blown fuses. If you find any blown fuses, replace them with new ones of the same rating. Additionally, check your relays for any signs of wear or damage. If you notice any damaged relays, replace them immediately.

In conclusion, inspecting your Harley’s electrical components is crucial for fixing the U0140 code. By checking your wiring, connectors, fuses, and relays, you can identify and fix any issues that may be causing a loss of communication with the body control module.

Body Control Module (BCM)

Function and Importance

The Body Control Module (BCM) is an essential component of your Harley-Davidson motorcycle. It is responsible for controlling various electrical systems such as lighting, turn signals, and ignition. The BCM also communicates with other modules in your motorcycle, such as the Engine Control Module (ECM) and the Transmission Control Module (TCM), to ensure that your motorcycle runs smoothly.

The BCM receives input from various sensors and switches in your motorcycle and sends output signals to control the various electrical systems. It is a complex system that relies on data networks to communicate with other modules and sensors.

BCM Issues

If your Harley-Davidson motorcycle is displaying a U0140 code, it means that there is a problem with the communication between the BCM and other modules in your motorcycle. This can be caused by a faulty BCM, damaged wires, or data network problems.

Replacing the BCM is a possible solution to fix the U0140 code, but it is important to make sure that the new BCM is programmed correctly to work with your motorcycle. Programming the new BCM is essential to ensure that it communicates with other modules and sensors in your motorcycle.

It is important to note that other issues can also cause the U0140 code to appear, such as an open or shorted BCM harness. It is recommended to have a professional mechanic diagnose and fix the issue to ensure that your motorcycle runs smoothly and safely.

In conclusion, the Body Control Module (BCM) is an essential component of your Harley-Davidson motorcycle that controls various electrical systems and communicates with other modules in your motorcycle. If you are experiencing issues with your BCM, it is important to have it diagnosed and fixed by a professional mechanic to ensure that your motorcycle runs smoothly and safely.

Troubleshooting Other Related Systems

When troubleshooting the U0140 code, it’s important to also check other related systems that could be causing the issue. Here are some common systems to check:

Door Locks and Keyless Entry

If you’re experiencing issues with your door locks or keyless entry system, it could be related to the U0140 code. Check your fuses and wiring connections to ensure they’re properly connected and not damaged. If you’re still experiencing issues, it may be time to replace the door lock actuator or keyless entry module.

Wipers and Washers

If your wipers and washers aren’t functioning properly, it could also be related to the U0140 code. Check your fuses and wiring connections to ensure they’re properly connected and not damaged. If you’re still experiencing issues, it may be time to replace the wiper motor or washer pump.

Remember, it’s important to properly diagnose the issue before replacing any parts. Don’t just replace parts based on the code alone, as it could end up being a waste of time and money. If you’re unsure about how to properly diagnose the issue, it’s always best to consult a professional mechanic.

By checking these related systems, you can ensure that you’re properly diagnosing and fixing the issue related to the U0140 code.

Advanced Diagnostics

If you’re experiencing the U0140 code on your Harley, it’s important to perform advanced diagnostics to determine the root cause of the problem. In this section, we’ll cover a few key areas to focus on during your diagnostics.

ABS and Speed Sensors

One common cause of the U0140 code is an issue with the ABS ECU relay. This can cause the ABS wheel speed difference to be too high, triggering the U0140 code. To diagnose this issue, you’ll need to check the ABS ECU relay for any signs of damage or wear. If the relay is in good condition, you’ll need to move on to the ABS wheel speed sensors.

Check the ABS wheel speed sensors for any signs of damage or wear, such as cracks or breaks. If the sensors are in good condition, you’ll need to perform a diagnostic test on the ABS system to determine if there are any issues with the speed sensors.

Engine and Transmission Correlations

Another potential cause of the U0140 code is an issue with the engine or transmission. If there is a problem with the engine or transmission, it can cause communication issues with the Body Control Module (BCM), triggering the U0140 code.

To diagnose this issue, you’ll need to check the engine and transmission for any signs of damage or wear. Check for any leaks, cracks, or other issues that could be causing communication problems with the BCM. You’ll also need to perform a diagnostic test on the engine and transmission to determine if there are any issues that need to be addressed.

Remember, the U0140 code can be caused by a variety of issues, so it’s important to perform thorough diagnostics to determine the root cause of the problem. By focusing on the ABS and speed sensors, as well as the engine and transmission, you’ll be able to identify and address the issue quickly and effectively.

Repair and Replacement

If you have determined that your Harley is experiencing a U0140 code, you will need to repair or replace the Body Control Module (BCM). Here are some things to consider when repairing or replacing the BCM.

When to Replace the BCM

If you have tried all the fixes and the U0140 code persists, it may be time to replace the BCM. Before replacing the BCM, you should have it diagnosed by a professional technician to ensure that it is indeed the cause of the problem. Replacing the BCM is not a simple task and requires specialized tools and knowledge.

Post-Repair Programming

After replacing the BCM, you will need to program it to work with your Harley. This programming is essential to ensure that the BCM is communicating properly with other systems in your Harley. The programming process requires specialized equipment and knowledge and should be performed by a professional technician.

When replacing the BCM, it is important to use a genuine Harley replacement part. Using a non-genuine part may cause compatibility issues and could lead to further problems down the road.

In summary, repairing or replacing the BCM is a complex process that requires specialized tools and knowledge. If you are not comfortable performing the repairs yourself, it is best to leave it to a professional technician. By following these guidelines, you can ensure that your Harley is running smoothly and safely.

Preventive Measures and Maintenance

To avoid encountering the U0140 code on your Harley, there are a few preventive measures you can take. One of the most important things you can do is to keep your bike well-maintained. Regular maintenance can help prevent issues with the Body Control Module (BCM) and other systems that can trigger the U0140 code.

Here are some tips for maintaining your Harley to prevent U0140 and other issues:

  • Keep your bike clean and dry to prevent corrosion. Corrosion can cause electrical connections to fail, leading to communication errors like the U0140 code.

  • Check your bike’s wiring regularly for signs of wear or damage. If you notice any frayed wires or other issues, have them repaired as soon as possible.

  • Make sure your battery is in good condition and properly charged. A weak or failing battery can cause all sorts of electrical issues, including communication errors like the U0140 code.

  • Follow the recommended maintenance schedule for your bike. This will help ensure that all systems are functioning properly and that any issues are caught and repaired before they can cause more serious problems.

  • If you do encounter the U0140 code, don’t ignore it. Have the issue diagnosed and repaired as soon as possible to prevent further damage to your bike’s electrical systems.

By following these preventive measures and keeping up with regular maintenance, you can help avoid issues with the U0140 code and other communication errors on your Harley.

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