U1595 – Vehicle Communication Bus Malfunction

The ODBII code U1595: Vehicle Communication Bus Malfunction indicates a problem with the communication network between various electronic control units (ECUs) in the vehicle, which may affect their ability to exchange data properly.

The severity of ODBII code U1595 is moderate.

Common Causes For: U1594 Lost Communication with the Body Control Module (BCM) – Bus Off.

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corrupted software or firmware in control modules
• Poor ground connections
• Short circuits or open circuits in the communication lines
• Interference from aftermarket devices
• Damaged or defective OBD-II port
• Low battery voltage or power supply issues

Common misdiagnosis for U1595 U1595: Vehicle Communication Bus Malfunction

• Faulty Engine Control Module (ECM)
• Defective Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Bad ground connections
• Malfunctioning sensors or actuators
• Issues with the powertrain control module (PCM)
• Corrupted software or firmware in modules
• Faulty diagnostic connectors or terminals
• Battery or charging system problems
• Intermittent communication issues due to environmental factors

Common Troubleshooting Steps

The OBD-II code U1595 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, which can affect the overall functionality of the vehicle’s systems. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors associated with the communication bus (CAN bus). Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the modules that are part of the communication network.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for continuity in the communication lines. Look for any short circuits or open circuits that could disrupt communication.
• Test the Modules: If possible, test the individual modules (e.g., Engine Control Module, Transmission Control Module, Body Control Module) for proper operation. A malfunctioning module can cause communication issues.
• If you have access to a scan tool that can communicate with individual modules, check if they respond correctly.
• Inspect the CAN Bus: Use an oscilloscope or a CAN bus analyzer to check the signal integrity on the CAN bus. Look for proper voltage levels and signal patterns.
• Ensure that the termination resistors (typically 120 ohms) are present and functioning correctly at both ends of the CAN bus.
• Check for Interference: Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication systems. This includes alarms, remote starters, or other electronic devices.
• Battery and Ground Connections: Ensure that the vehicle’s battery is in good condition and that all ground connections are secure. Poor power or ground can lead to communication issues.
• Software Updates: Check if there are any available software updates for the vehicle’s modules. Sometimes, manufacturers release updates to fix known communication issues.
• Clear Codes and Test Drive: After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the U1595 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues.1
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues. By following these steps, you should be able to identify and resolve the underlying cause of the U1595 code.