U1877 – Network Communication Line Fault

The ODBII code U1877 indicates a fault in the network communication line, suggesting a problem with the data transmission between modules in the vehicle’s communication network.

The severity of ODBII code U1877 is moderate.

Common Causes For: U1876 U1876: “Control Module Communication Failure”

• Faulty wiring or connectors
• Short circuits in the communication line
• Open circuits in the communication line
• Malfunctioning control modules
• Corroded or damaged terminals
• Interference from aftermarket devices
• Poor ground connections
• Software issues or bugs in the modules
• Faulty or damaged communication bus (CAN bus) components
• Electrical noise or interference in the system

Common misdiagnosis for U1877 U1877: “Network Communication Line Fault”

• Faulty wiring or connectors
• Defective control modules
• Incorrectly configured or programmed modules
• Issues with the CAN bus system
• Power supply problems
• Grounding issues
• Intermittent communication faults
• Software glitches in modules

Common Troubleshooting Steps

The OBD-II code U1877 indicates a “Network Communication Line Fault,” which typically points to an issue with the communication between various modules in the vehicle’s network. 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 network (CAN bus, LIN bus, etc.). Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors at the modules involved in the communication.
• Test the Communication Network:
• Use a multimeter to check for continuity and resistance in the communication lines. Ensure that the wires are not shorted to ground or to each other.
• If available, use a scan tool that can monitor the communication between modules to see if any specific module is not responding.
• Check Power and Ground:
• Ensure that all modules on the network have proper power and ground connections. A lack of power or a poor ground can cause communication issues.
• Inspect Modules:
• If a specific module is suspected to be the cause, inspect it for damage or malfunction. This may include checking for water intrusion, physical damage, or internal faults.
• If possible, swap the suspected module with a known good one to see if the issue resolves.
• Look for Interference:
• Check for any aftermarket devices or modifications that may interfere with the vehicle’s communication network. This includes alarm systems, stereo systems, or other electronic devices.
• Perform a Network Test:
• Some advanced scan tools can perform a network test to check the integrity of the communication lines and identify any faults.
• Clear Codes and Test Drive:
• After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code reappears.
• Consult Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures related to the communication network and the U1877 code.
• Seek Professional Help:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with automotive electronics and communication systems. By following these steps, you should be able to identify and resolve the underlying issue causing the U1877 code.