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Harley Code U0159: Understanding the Diagnostic Trouble Code

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Chase Manhattan

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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, it is essential to be familiar with diagnostic trouble codes (DTCs). One of the most common DTCs that Harley riders encounter is the U0159 code, which indicates a lost communication with the park assist control module A. This code can cause the engine light to turn on or the service engine soon warning light to appear on your dashboard.

The U0159 code is usually caused by a communication problem between the powertrain control module (PCM) and the fuel injection control module (FICM). It can also be caused by a malfunctioning park assist control module A or a problem with the CAN bus network. The CAN bus is a communication system that allows different modules in your motorcycle to communicate with each other.

If you encounter the U0159 code, it is important to diagnose and fix the problem as soon as possible. Ignoring this code can lead to other problems and potentially cause damage to your motorcycle. In the following sections, we will discuss how to diagnose and fix the U0159 code, as well as provide some tips on how to prevent it from happening in the future.

Understanding Harley Code U0159

If you own a Harley-Davidson motorcycle, you might have come across a situation where the engine light turns on or the service engine soon warning light appears. This could be due to several reasons, one of which is a communication problem between the powertrain control module (PCM) and the fuel injection control module (FICM). This is indicated by the U0159 fault code.

Significance of Code U0159

Code U0159 represents a lost communication with the parking assist control module A (PACM-A). The PACM-A is responsible for controlling the parking sensors and sending the data to the body control module (BCM). The BCM then sends this information to the electronic control module (ECM) to display the parking assist information on the gauge cluster.

When the ECM detects a loss of communication with the PACM-A, it sets the U0159 code. This code indicates that the ECM is not receiving any data from the PACM-A, which can cause the parking assist system to malfunction.

Common Causes for U0159

The most common cause of the U0159 code is a loss of power or ground to the PACM-A. This could be due to a blown fuse or a loose connection. Another possible cause is a faulty PACM-A module, which may need to be replaced.

In some cases, the U0159 code may be caused by a problem with the CAN bus, which is responsible for transmitting data between the different modules in the motorcycle. A malfunctioning CAN bus can cause communication errors between the modules, including the PACM-A.

In conclusion, the U0159 code is an indication of a communication problem between the PACM-A and the ECM. This can be caused by several factors, including a faulty PACM-A module, a blown fuse, a loose connection, or a malfunctioning CAN bus. If you encounter this code, it is recommended to consult with a certified Harley-Davidson technician to diagnose and repair the issue.

Diagnostic Trouble Codes (DTCs) Overview

If you own a Harley-Davidson motorcycle, you may have heard of Diagnostic Trouble Codes (DTCs). These codes are alphanumeric codes that are generated by the onboard computer system of your bike. They are designed to alert you to potential issues within various systems of your motorcycle, such as the engine, transmission, or electrical components.

How DTCs are Set

DTCs are set when the Engine Control Unit (ECU) detects a fault in one of the sensors or circuits of your motorcycle. The ECU monitors various sensors, such as the Crankshaft Position Sensor (CKP), Heated Oxygen Sensor (HO2S), Manifold Absolute Pressure (MAP) sensor, Throttle Position Sensor (TPS), and Vehicle Speed Sensor (VSS). When the ECU detects a fault, it stores a code in its memory and illuminates the Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) on your dashboard.

Reading and Interpreting DTCs

To read and interpret DTCs on your Harley-Davidson motorcycle, you will need a diagnostic tool, such as a Digital Technician II (DTII) or a Harley-Davidson Scan Tool. These tools can communicate with your motorcycle’s ECU and retrieve the stored codes.

Once you have retrieved the codes, you can use a service manual or online resources to interpret them. Each DTC consists of a letter followed by four digits. The letter indicates the system that is affected, such as P for Powertrain, B for Body, or C for Chassis. The four digits indicate the specific fault, such as U0159 for Lost Communication with Park Assist Control Module A.

It is important to note that DTCs are not always accurate and may require further diagnosis to determine the root cause of the fault. Additionally, some DTCs may be stored in the ECU’s memory even if the fault has been resolved. To clear the codes, you will need to use a diagnostic tool or disconnect the battery for a few minutes.

In summary, DTCs are an essential tool for diagnosing issues with your Harley-Davidson motorcycle. Understanding how they are set and how to read and interpret them can help you identify and resolve problems quickly and efficiently.

Harley’s Electrical System

If you are a Harley-Davidson owner, you know that the electrical system is a crucial component of your bike. It powers everything from your ignition system to your lights and radio. Understanding how your Harley’s electrical system works can help you diagnose and fix problems that may arise.

Battery and Ignition System

The battery and ignition system are the heart of your Harley’s electrical system. The battery provides the power to start your bike and run all of the electrical components. The ignition system is responsible for starting your engine and keeping it running. If your battery or ignition system fails, your bike won’t start.

To keep your battery and ignition system in good condition, it’s important to perform regular maintenance. This includes checking the battery’s charge level, cleaning the battery terminals, and inspecting the ignition system for wear and tear.

Module Communications

Harley’s electrical system also includes modules that communicate with each other via a Controller Area Network (CAN). These modules include the Engine Control Module (ECM), Body Control Module (BCM), and Speedometer (SPDO).

When a problem occurs, these modules can generate Diagnostic Trouble Codes (DTCs) that can help you diagnose the issue. For example, the U0159 DTC indicates a communication problem between the Parking Assist Control Module and the Body Control Module.

To diagnose and fix module communication problems, you’ll need a diagnostic tool that can read DTCs and communicate with the modules. Harley-Davidson offers a range of diagnostic tools that can help you diagnose and fix electrical problems on your bike.

In conclusion, understanding how your Harley’s electrical system works is essential for keeping your bike running smoothly. By performing regular maintenance and using diagnostic tools when problems arise, you can keep your bike on the road and enjoy the ride.

CAN Bus Network Explained

If you’re dealing with a Harley-Davidson fault code U0159, it’s likely related to the CAN bus network. Understanding how the CAN bus works can help you diagnose and troubleshoot issues more effectively.

CAN Bus Functionality

CAN stands for Controller Area Network, which is a communication protocol used in modern vehicles to allow different systems to communicate with each other. The CAN bus network is made up of two wires – CAN High and CAN Low – that transmit data between different modules in the vehicle.

In a Harley-Davidson motorcycle, the Engine Control Module (ECM) and Body Control Module (BCM) are two of the most important modules that communicate over the CAN bus network. The ECM controls the engine and transmission, while the BCM controls other systems like lighting, audio, and security.

Troubleshooting CAN Bus Issues

If you’re experiencing a U0159 fault code or other issues related to the CAN bus network, there are a few things you can try to troubleshoot the problem:

  • Check the connections: Make sure all the connections between the different modules in the vehicle are secure and free from corrosion or damage.

  • Check the wiring: Inspect the wiring harnesses for any damage or wear that could be causing a short or open circuit.

  • Check the modules: Use a diagnostic tool to check for any fault codes related to the ECM or BCM. If there are any other codes present, address those first before trying to diagnose the U0159 code.

  • Check the inputs: If the BCM is not receiving input from a sensor or switch, it may not be able to communicate over the CAN bus network. Check the inputs to make sure they are functioning properly.

By understanding how the CAN bus network works and following these troubleshooting steps, you can diagnose and fix issues related to Harley-Davidson fault code U0159.

Motorcycle Control Modules

When it comes to modern Harley-Davidson motorcycles, there are two main types of control modules that are responsible for managing various systems on the bike. These are the Engine Control Module (ECM) and the Body Control Module (BCM). The two modules communicate with each other over a network known as the CAN bus.

Engine Control Module (ECM)

The ECM is responsible for managing the engine and related systems on the motorcycle. It receives input from various sensors on the bike and uses this information to adjust fuel delivery, ignition timing, and other parameters to ensure optimal performance. The ECM also communicates with other modules on the bike over the CAN bus to coordinate various functions.

Body Control Module (BCM)

The BCM is responsible for managing various non-engine related systems on the motorcycle. This includes things like the lighting system, instrument cluster, and audio system. The BCM also communicates with other modules on the bike over the CAN bus to coordinate various functions.

When there is a problem with communication between the modules, a code such as U0159 may be set. This code indicates that there is a communication problem between the modules, which can be caused by a variety of issues such as a faulty module or a wiring problem.

It is important to note that the CAN bus system is a complex network, and diagnosing communication problems can be challenging. In some cases, it may be necessary to use specialized diagnostic equipment to pinpoint the issue.

In summary, the ECM and BCM are critical components of modern Harley-Davidson motorcycles, responsible for managing various systems on the bike. When there is a communication problem between these modules, a code such as U0159 may be set, indicating that further diagnosis is required.

Sensor and Switch Inputs

Critical Sensors for Harley

Harley-Davidson motorcycles are equipped with various sensors that play a critical role in ensuring that the motorcycle runs smoothly. Some of the critical sensors that you should be aware of include:

  • Intake Air Temperature (IAT) Sensor: The IAT sensor measures the temperature of the air entering the engine. This information is used by the Engine Control Module (ECM) to adjust the fuel injection and ignition timing to ensure optimal performance.

  • Intake Air Pressure (ISS) Sensor: The ISS sensor measures the pressure of the air entering the engine. This information is used by the ECM to adjust the fuel injection and ignition timing to ensure optimal performance.

  • Throttle Position Sensor (TPS): The TPS measures the position of the throttle valve. This information is used by the ECM to adjust the fuel injection and ignition timing to ensure optimal performance.

Switch Inputs and Motorcycle Safety

Switch inputs are also an essential part of Harley-Davidson motorcycles. These inputs are used to control various functions of the motorcycle and ensure the rider’s safety. Some of the switch inputs that you should be aware of include:

  • Run/Stop Switch: The Run/Stop switch is used to turn the motorcycle on and off. It is a critical safety feature that ensures that the motorcycle does not start accidentally.

  • Turn Signal Switch: The Turn Signal switch is used to signal the rider’s intention to turn left or right. It is a critical safety feature that ensures that other motorists are aware of the rider’s intentions.

  • Security System: The Security System is used to protect the motorcycle from theft. It is a critical safety feature that ensures that the motorcycle is secure when parked.

  • Cruise Control: The Cruise Control system is used to maintain a constant speed while riding. It is a critical safety feature that ensures that the rider does not have to constantly adjust the throttle.

In conclusion, understanding the critical sensors and switch inputs of your Harley-Davidson motorcycle is essential to ensure optimal performance and rider safety. By familiarizing yourself with these inputs, you can ensure that your motorcycle runs smoothly and safely.

Troubleshooting and Repair Strategies

If the U0159 trouble code is showing up on your Harley, it’s important to take action quickly to prevent further damage to your motorcycle. Here are some troubleshooting and repair strategies you can use to diagnose and fix the issue.

Step-by-Step Diagnostic Process

  1. Start by checking the communication lines between the PACM-A and other modules. Look for any damaged or corroded wires, loose connections, or other issues that could be causing a loss of communication.

  2. Use a diagnostic tool to check for any other trouble codes that may be present. This can help you identify any additional issues that need to be addressed.

  3. Check the power and ground connections to the PACM-A module. Make sure all fuses that power up the PACM-A module are in good condition.

  4. If you’re still unable to locate the problem, it may be necessary to replace the PACM-A module entirely.

Repair and Replacement Tips

If you’ve identified the issue and need to make repairs or replace parts, here are some tips to keep in mind:

  • Always use OEM parts when possible. Aftermarket parts may not be compatible with your motorcycle’s systems and could cause further issues.

  • When replacing parts, be sure to follow the manufacturer’s instructions carefully. This will ensure that the new parts are installed correctly and will function properly.

  • If you’re not comfortable making repairs yourself, it’s always best to take your motorcycle to a professional mechanic. They will have the knowledge and experience to diagnose and fix the issue quickly and accurately.

By following these troubleshooting and repair strategies, you can get your Harley back on the road quickly and safely. Remember to always take care when working on your motorcycle and to follow all safety guidelines to prevent accidents or injuries.

Harley Code U0159 Specific Fixes

If you are experiencing the U0159 trouble code on your Harley, there are a few specific fixes that you can try to resolve the issue. The U0159 code indicates that there is a communication problem between the ECM and the Park Assist Control Module (PACM-A). Here are some possible solutions:

  • Check the CAN bus wiring: The CAN bus is the communication network that connects all of the electronic modules on your Harley. If there is a problem with the wiring, it can cause communication errors between the modules. Inspect the wiring for any damage or corrosion, and make sure that all connections are secure.

  • Check the PACM-A wiring: The PACM-A is the module responsible for controlling the park assist system on your Harley. If there is a problem with the wiring, it can cause the U0159 code to appear. Inspect the wiring for any damage or corrosion, and make sure that all connections are secure.

  • Check the PACM-A module: If the wiring is not the problem, it is possible that the PACM-A module itself is faulty. You can test the module using a diagnostic tool to see if it is communicating properly with the ECM. If the module is faulty, it will need to be replaced.

  • Check the ECM module: The ECM is the module responsible for controlling the engine and other systems on your Harley. If there is a problem with the ECM, it can cause communication errors with other modules, including the PACM-A. You can test the ECM using a diagnostic tool to see if it is communicating properly with the PACM-A. If the ECM is faulty, it will need to be replaced.

  • Clear the trouble code: Once you have identified and fixed the problem, you will need to clear the U0159 trouble code from the system. You can do this using a diagnostic tool or by disconnecting the battery for a few minutes.

In summary, the U0159 trouble code on your Harley indicates a communication problem between the ECM and the PACM-A. To fix the issue, you should check the wiring, test the modules, and clear the trouble code. If you are not comfortable performing these tasks yourself, it is recommended that you take your Harley to a qualified mechanic for diagnosis and repair.

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