U1997 – Communication Network Malfunction

The ODBII code U1997: Communication Network Malfunction indicates a failure in the communication between various control modules in the vehicle’s network, which can affect their ability to exchange data properly.

The severity of ODBII code **U1997: Communication Network Malfunction** is generally considered moderate to severe.

Common Causes For: U1993: Inter-Module Communication Failure

• Faulty wiring or connectors in the communication network.
• Malfunctioning control modules.
• Corrupted software or firmware in control modules.
• Poor ground connections.
• Interference from aftermarket devices.
• Damaged or shorted communication lines.
• Low battery voltage or power supply issues.
• Faulty or damaged CAN bus transceivers.

Common misdiagnosis for U1997: Communication Network Malfunction

• Faulty wiring or connectors
• Defective control modules
• Battery or power supply issues
• Software glitches or outdated firmware
• Intermittent communication issues
• Grounding problems
• Faulty sensors or actuators
• Corrupted data or configuration errors

Common Troubleshooting Steps

The OBD-II code **U1997: Communication Network Malfunction** indicates a problem with the communication between various modules in the vehicle’s network. This can affect systems like the engine control module (ECM), transmission control module (TCM), and other electronic control units (ECUs). 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. Look for damaged, corroded, or loose connections.
• Pay special attention to the connectors for the modules involved in the communication network.
• Check for Short Circuits or Open Circuits:
• Use a multimeter to check for continuity in the communication lines. Look for any short circuits or open circuits that could disrupt communication.
• Verify Power and Ground:
• Ensure that all modules have the proper power supply and ground connections. A lack of power or a poor ground can cause communication issues.
• Inspect the CAN Bus:
• If your vehicle uses a Controller Area Network (CAN) bus, check the bus for proper voltage levels. The typical voltage levels should be around 2.5V for CAN High and CAN Low.
• Use an oscilloscope if available to check for proper signal waveforms on the CAN lines.
• Check for Module Malfunction:
• If a specific module is suspected to be faulty, try disconnecting it and see if the code clears. If it does, the module may need to be repaired or replaced.
• Look for Interference:
• Check for any aftermarket devices or modifications that may interfere with the vehicle’s communication network, such as alarms, remote starters, or audio systems.
• Perform a Network Scan:
• Use a professional-grade scan tool to perform a network scan. This can help identify which modules are not communicating properly.
• Update Software/Firmware:
• Check if there are any software or firmware updates available for the vehicle’s modules. Sometimes, updating the software can resolve communication issues.
• 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 returns. 1
• Consult Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures related to the communication network for your make and model. If the issue persists after following these steps, it may be necessary to consult a professional technician or dealership for further diagnosis and repair.