U1979 – Module Communication Failure

The ODBII code U1979 indicates a “Module Communication Failure,” meaning there is a problem with communication between vehicle control modules, often due to a fault in the wiring, connectors, or the modules themselves.

The severity of ODBII code U1979 is moderate.

Common Causes For: U1978 U1978: “Module Communication Failure”

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Poor ground connections
• Corrupted software or firmware in the module
• Interference from aftermarket devices
• Low battery voltage or power supply issues
• Communication network issues (e.g., CAN bus problems)

Common misdiagnosis for U1979 U1979: “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 U1979 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(s). 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 affected module 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.
• Inspect the CAN Bus:
• The Controller Area Network (CAN) bus is responsible for communication between modules. Check for any faults in the CAN bus wiring.
• Use an oscilloscope or a CAN bus diagnostic tool to monitor the bus for proper signals.
• Check for Interference: Look for any aftermarket devices or modifications that may be interfering with the communication between modules.
• Reset the Modules: Sometimes, simply resetting the modules can resolve communication issues. Disconnect the battery for a few minutes, then reconnect it and see if the code returns.
• Update Software/Firmware: Check if there are any software or firmware updates available for the vehicle’s modules. Sometimes, communication issues can be resolved with an update.
• 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 known communication issues.
• 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 address the root cause of the U1979 code.