U2491 – Module Communication Failure

The ODBII code U2491 indicates a communication failure between modules in a vehicle’s network, suggesting that one or more control modules are unable to communicate properly with each other.

The severity of ODBII code U2491 is generally considered moderate.

Common Causes For: U2490 U2490: “Module Communication Failure”

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Poor ground connections
• Intermittent communication issues
• Software or firmware issues
• Corroded terminals
• Electrical interference
• Low battery voltage or weak battery
• Damaged or frayed harnesses
• Incompatible or aftermarket components

Common misdiagnosis for U2491 U2491: “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 U2491 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. Use a multimeter to check the power supply to the module.
• Verify that the fuses related to the module are intact and functioning.
• Test the Module:
• If possible, test the affected module by swapping it with a known good module (if applicable) to see if the problem persists.
• Some modules may have self-diagnostic capabilities; check for any internal fault codes.
• Inspect the CAN Bus:
• If the vehicle uses a Controller Area Network (CAN) bus for communication, check the integrity of the CAN bus wiring.
• Use an oscilloscope or a CAN bus diagnostic tool to monitor the bus for proper signal levels and communication.
• Check for Interference:
• Look for any aftermarket devices or modifications that may interfere with the communication between modules.
• Disconnect any non-factory accessories to see if the issue resolves.
• Update Software/Firmware:
• Check if there are any software or firmware updates available for the affected module(s). Sometimes, communication issues can be resolved with an update.
• Perform a Hard Reset:
• Disconnect the vehicle’s battery for a few minutes to reset the modules. Reconnect and see if the code reappears.
• 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, consider seeking help from a professional mechanic or dealership with advanced diagnostic tools. By following these steps, you should be able to identify and resolve the underlying cause of the U2491 code.