U1987 – Module Communication Failure

The ODBII code U1987 indicates a “Module Communication Failure,” meaning there is a problem with communication between the vehicle’s control modules, often due to a wiring issue, a faulty module, or a network problem.

The severity of ODBII code U1987 is moderate.

Common Causes For: U1986 U1986: “Module Communication Failure”

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Poor ground connections
• Intermittent electrical issues
• Software or firmware issues
• Corroded terminals
• Low battery voltage
• Communication network issues (e.g., CAN bus problems)

Common misdiagnosis for U1987 U1987: “Module Communication Failure”

• Faulty wiring or connectors
• Defective control module
• Software issues or updates needed
• Battery or power supply problems
• Grounding issues
• Intermittent communication issues
• Other unrelated module failures

Common Troubleshooting Steps

The OBD-II code U1987 indicates a “Module Communication Failure,” which typically means that there is a problem with communication between the vehicle’s control modules. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Other 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 affected module. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check Power Supply: Ensure that the module in question is receiving the proper voltage and ground. Use a multimeter to check the power supply to the module.
• Test the Module: If possible, test the affected module to ensure it is functioning correctly. This may involve using specialized diagnostic tools or swapping the module with a known good one.
• Check for Interference: Look for any aftermarket devices or modifications that may interfere with the communication between modules. This includes things like alarm systems, stereo systems, or other electronic accessories.
• Inspect the CAN Bus: If the vehicle uses a Controller Area Network (CAN) bus for communication, check the integrity of the CAN bus wiring. Look for shorts, opens, or other issues that could disrupt communication.
• 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 reappears.
• Update Software/Firmware: In some cases, updating the software or firmware of the affected module may resolve communication issues. Check with the manufacturer for any available updates.
• 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 module communication.
• Professional Diagnosis: If the issue persists after performing the above steps, it may be necessary to seek the assistance of a professional mechanic or dealership with advanced diagnostic equipment. By following these steps, you can systematically identify and address the underlying cause of the U1987 code.