U1850 – Module Communication Failure

The ODBII code U1850 indicates a “Module Communication Failure,” meaning that there is a problem with communication between the vehicle’s control modules, often due to a fault in the wiring, connectors, or the modules themselves.

The severity of ODBII code U1850 is moderate.

Common Causes For: U1849 U1849: Instrument Cluster Communication Failure

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Corrupted software or firmware in the module
• Poor ground connections
• Intermittent electrical issues
• Communication network issues (e.g., CAN bus problems)
• Battery voltage issues
• Corrosion or damage in connectors or terminals

Common misdiagnosis for U1850 U1850: “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 communication protocol failures

Common Troubleshooting Steps

The OBD-II code U1850 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 modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the wiring harnesses that connect the modules, as these can be prone to wear and tear.
• Check Power and Ground:
• Ensure that the affected module(s) are receiving proper power and ground. Use a multimeter to check voltage at the module’s power and ground pins.
• If there is no power or ground, trace the wiring back to the source to identify any breaks or shorts.
• Test the Communication Bus:
• Use a scan tool to monitor the communication bus (CAN bus, LIN bus, etc.) for activity. If there is no communication, it may indicate a fault in the bus itself.
• Check for short circuits or open circuits in the communication lines.
• Check for Module Malfunction:
• If the wiring and connections are good, the issue may lie with the module itself. If possible, test the module in another vehicle or replace it with a known good module to see if the problem persists.
• Inspect for Interference:
• Look for any aftermarket devices or modifications that may interfere with the communication between modules. This includes alarm systems, stereo systems, or other electronic devices.
• Clear Codes and Test Drive:
• After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures related to the U1850 code and the modules involved. This can provide additional insights and steps tailored to your vehicle.
• Professional Diagnosis:
• If the issue persists after performing these steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues. By following these steps, you should be able to identify and resolve the underlying cause of the U1850 code.