U1879 – Control Module Communication Failure

The ODBII code U1879 indicates a “Control Module Communication Failure,” meaning there is a problem with communication between the vehicle’s control modules, which can affect various systems and functions.

The severity of ODBII code U1879 is moderate.

Common Causes For: U1878 U1878: Control Module Communication Failure

• Faulty wiring or connectors
• Failed control module
• Poor ground connections
• Corroded or damaged connectors
• Communication network issues (e.g., CAN bus problems)
• Software or firmware issues in control modules
• Low battery voltage or power supply issues
• Interference from aftermarket devices or modifications

Common misdiagnosis for U1879 U1879: “Control Module Communication Failure”

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or power supply problems
• Intermittent connection issues
• Communication network faults (CAN bus issues)

Common Troubleshooting Steps

The OBD-II code U1879 indicates a “Control Module Communication Failure.” This code typically suggests that there is a problem with the communication between various control modules in the vehicle. 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 additional trouble codes. Sometimes, other codes can provide context or lead to the root cause of the communication failure.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the control modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the wiring harnesses that connect the affected modules.
• Check Power and Ground:
• Ensure that the control modules have proper power and ground connections. Use a multimeter to check voltage and ground continuity.
• If a module is not receiving power or ground, trace the circuit back to find the issue.
• Test Control Modules:
• If possible, test the affected control modules individually to ensure they are functioning correctly. This may involve using specialized diagnostic tools or swapping with known good modules.
• Inspect the CAN Bus:
• The communication between control modules often occurs over a Controller Area Network (CAN) bus. Check the integrity of the CAN bus wiring and connections.
• Use a CAN bus scanner to monitor the communication and check for any abnormalities.
• Look for Interference:
• Check for any aftermarket devices or modifications that may interfere with the communication between modules. This includes alarm systems, stereo systems, or other electronic devices.
• Reset the Modules:
• Sometimes, simply resetting the control modules can resolve communication issues. Disconnect the battery for a few minutes, then reconnect it and see if the code returns.
• Update Software/Firmware:
• In some cases, a software update for the control modules may be necessary. Check with the manufacturer for any available updates.
• Consult Technical Service Bulletins (TSBs):
• Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to U1879.
• Professional Diagnosis:
• If the issue persists after performing the above steps, it may be necessary to seek help from a professional mechanic or dealership with advanced diagnostic equipment. By following these steps, you can systematically identify and resolve the underlying cause of the U1879 code.