U1993 – Inter-Module Communication Failure

The ODBII code U1993: Inter-Module Communication Failure indicates a problem with communication between different control modules in a vehicle, suggesting that one or more modules are not able to send or receive data properly.

The severity of ODBII code **U1993: Inter-Module Communication Failure** is generally considered moderate to severe.

Common Causes For: U1989: Module Communication Failure

• Faulty wiring or connectors
• Failed control module
• Corrupted software or firmware
• Poor ground connections
• Intermittent electrical issues
• Low battery voltage
• Communication network issues (e.g., CAN bus problems)
• Damaged or corroded pins in connectors
• Incompatible aftermarket components
• Faulty sensors or actuators affecting communication

Common misdiagnosis for U1993: Inter-Module Communication Failure

• Faulty wiring or connectors
• Defective control modules
• Software issues or firmware bugs
• Power supply problems
• Grounding issues
• Communication protocol mismatches
• Corrupted data or signals
• Interference from aftermarket devices

Common Troubleshooting Steps

The OBD-II code **U1993: Inter-Module Communication Failure** indicates a problem with communication between different modules in a vehicle’s network. This can affect various systems, including the engine control unit (ECU), transmission control unit (TCU), and other electronic modules. 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, U-codes can be related to other issues that can provide more context.
• Inspect Wiring and Connectors:
• Visually inspect the wiring harnesses and connectors associated with the modules involved. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to ground connections, as poor grounding can lead to communication issues.
• Check for Module Power Supply:
• Ensure that all relevant modules are receiving proper power. Use a multimeter to check voltage at the connectors.
• Verify that fuses related to the communication network are intact.
• Test Communication Lines:
• Use a scan tool to check the communication status of the modules. Some scan tools can perform a network test to see if modules are communicating properly.
• If possible, use an oscilloscope to check the data lines for proper signal patterns.
• 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.
• Reset the Modules:
• Clear the trouble codes using the OBD-II scanner and see if the code returns. Sometimes, a temporary glitch can cause communication failures.
• Update Software/Firmware:
• Check if there are any software updates available for the vehicle’s modules. Sometimes, manufacturers release updates to fix communication issues.
• Perform a Network Scan:
• If available, use a more advanced diagnostic tool to perform a network scan to identify which module is not communicating properly.
• Check for Short Circuits:
• Inspect the wiring for any short circuits that could be causing communication failures. This may require more in-depth testing with a multimeter.
• Replace Faulty Modules:
• If a specific module is identified as the source of the problem and all other troubleshooting steps have been exhausted, consider replacing the faulty module. 1
• Consult Technical Service Bulletins (TSBs):
• Check for any TSBs related to the specific make and model of the vehicle, as manufacturers may have documented solutions for known communication issues. 1
• Seek Professional Help:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership with specialized diagnostic equipment. By following these steps, you can systematically diagnose and potentially resolve the U1993 code and any underlying communication issues in the vehicle’s network.