U1994 – Inter-Module Communication Failure

The ODBII code U1994 indicates a communication failure between modules in a vehicle’s network, suggesting that one or more electronic control units (ECUs) are unable to exchange data properly.

The severity of ODBII code U1994: Inter-Module Communication Failure is generally considered moderate.

Common Causes For: 1. U1964: Module Communication Failure

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

Common misdiagnosis for 1. U1994: Inter-Module Communication Failure

• Faulty wiring or connectors
• Defective control modules
• Software issues or updates needed
• Battery or power supply problems
• Grounding issues
• Interference from aftermarket devices
• Incorrectly configured or programmed modules
• Communication protocol mismatches

Common Troubleshooting Steps

When dealing with OBD-II code U1994, which indicates an “Inter-Module Communication Failure,” it’s important to follow a systematic approach to troubleshoot the issue. Here are some common troubleshooting steps:

• Check for Other Codes: Start by scanning the vehicle for any additional trouble codes. U1994 may be accompanied by other codes that can provide more context about the issue.
• Inspect Wiring and Connectors: Examine the wiring and connectors associated with the modules involved in communication. Look for signs of damage, corrosion, or loose connections. Pay special attention to the CAN (Controller Area Network) bus wiring.
• Check Power and Ground: Ensure that the affected modules have proper power and ground connections. Use a multimeter to verify voltage and ground integrity.
• Test the Modules: If possible, test the modules involved in the communication. This may involve using a scan tool to check for module responses or performing specific tests as outlined in the vehicle’s service manual.
• Inspect the CAN Bus: If the vehicle uses a CAN bus system, check for continuity and resistance in the CAN wires. Look for shorts to ground or power, and ensure that the bus is not open.
• Check for Interference: Sometimes, aftermarket accessories or modifications can interfere with module communication. Remove or disconnect any non-factory components to see if the issue resolves.
• Update Software/Firmware: In some cases, a software update for the vehicle’s modules may be necessary. Check with the manufacturer for any available updates.
• 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): Check for any TSBs related to U1994 for your specific vehicle make and model. Manufacturers may have issued guidance on common issues and fixes.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional technician or a dealership with advanced diagnostic tools. By following these steps, you can systematically identify and address the underlying cause of the U1994 code.