U1998 – Module Communication Failure

The ODBII code U1998 indicates a communication failure between modules in the vehicle’s network, suggesting that one or more electronic control units (ECUs) are not able to communicate properly with each other.

The severity of ODBII code U1998: Module Communication Failure is generally considered moderate to severe, depending on the specific vehicle and the affected systems.

Common Causes For: 1. U1994: Inter-Module Communication Failure

• Faulty wiring or connectors
• Malfunctioning control modules
• Poor ground connections
• Interference from aftermarket devices
• Software issues or bugs in the modules
• Low battery voltage or power supply issues
• Corroded or damaged pins in connectors
• Communication network issues (e.g., CAN bus problems)

Common misdiagnosis for 1. U1998: 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 module failures (e.g., ABS, BCM)
• Incorrectly installed aftermarket accessories

Common Troubleshooting Steps

When dealing with OBD-II code U1998, which indicates a “Module Communication Failure,” it typically means that there is a communication issue between the vehicle’s control modules. Here are some common troubleshooting steps to help diagnose and resolve the issue:

• Check for Other Codes: Start by scanning the vehicle for any other diagnostic trouble codes (DTCs). Other codes may provide additional context or indicate which module is having communication issues.
• Inspect Wiring and Connectors: Examine the wiring and connectors associated with the affected modules. Look for signs of damage, corrosion, loose connections, or broken wires. Pay special attention to ground connections, as poor grounding can lead to communication failures.
• Verify Power Supply: Ensure that the affected modules are receiving the proper voltage and ground. Use a multimeter to check the power and ground circuits for continuity and proper voltage levels.
• Check for Module Updates: Sometimes, communication issues can be resolved by updating the software in the affected modules. Check with the manufacturer or a dealership to see if there are any available updates.
• Inspect the CAN Bus: The Controller Area Network (CAN) bus is responsible for communication between modules. Use a scan tool to monitor the CAN bus for any irregularities. Look for short circuits, open circuits, or other issues that may affect communication.
• Test Individual Modules: If you suspect a specific module is causing the issue, you can test it individually. Disconnect the module and see if the communication error persists. If the error goes away, the module may be faulty.
• Check for Interference: Sometimes, aftermarket accessories or modifications can interfere with module communication. If any recent changes have been made to the vehicle, consider removing them temporarily to see if the issue resolves.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the modules. Reconnect the battery and see if the code reappears.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on known communication issues.
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its systems. By following these troubleshooting steps, you can systematically identify and resolve the communication failure indicated by the U1998 code.