U1571 – Communication Bus Off.

The ODBII code U1571 indicates a communication issue where a module on the vehicle’s communication bus is not responding or is offline, potentially due to a fault in the wiring, connectors, or the module itself.

The severity of ODBII code U1571 Communication Bus Off is moderate to severe.

Common Causes For: U1570 Communication Bus Off.

• Faulty wiring or connectors in the communication bus.
• Malfunctioning control modules.
• Short circuits or open circuits in the bus lines.
• Interference from aftermarket devices.
• Software issues or bugs in the control modules.
• Low battery voltage or power supply issues.
• Corrosion or damage to connectors.

Common misdiagnosis for U1571 Communication Bus Off.

• Faulty ABS module
• Defective engine control module (ECM)
• Malfunctioning transmission control module (TCM)
• Wiring issues or shorts in the communication lines
• Bad ground connections
• Faulty sensors
• Incorrectly diagnosed battery or charging system issues
• Issues with the body control module (BCM)

Common Troubleshooting Steps

The OBD-II code U1571 indicates a communication issue related to the vehicle’s communication bus, specifically that a module is reporting a “Communication Bus Off” condition. This can be caused by various factors, including wiring issues, module failures, or problems with the communication network itself. Here are some common troubleshooting steps to diagnose and resolve the U1571 code:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context about the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors related to the communication bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors of the modules involved in the communication network.
• Check Power and Ground: Ensure that the affected modules have proper power and ground connections. Use a multimeter to verify voltage and ground continuity.
• Test the Communication Network: Use a scan tool to monitor the communication between modules. Check if other modules are communicating properly.
• If possible, use an oscilloscope to check the signal integrity on the communication lines (CAN, LIN, etc.).
• Inspect Modules: Identify which module is reporting the U1571 code. If possible, test the module for proper operation.
• If the module is suspected to be faulty, consider replacing it or reprogramming it if necessary.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for short circuits or open circuits in the communication lines. This may involve checking continuity between modules.
• Look for Interference: Check for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarms, stereo systems, or other electronic devices.
• 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): Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to the U1571 code.
• Seek Professional Help: 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 issue causing the U1571 code.