U1974 – Module Communication Failure

The ODBII code U1974 indicates a “Module Communication Failure,” meaning there is a problem with communication between vehicle control modules, often due to a wiring issue, a faulty module, or a network problem.

The severity of ODBII code U1974 is moderate.

Common Causes For: U1973 Lost Communication with the Hybrid Powertrain Control Module (HPCM) A.

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Poor ground connections
• Corrupted software or firmware in the module
• Interference from aftermarket devices
• Low battery voltage or power supply issues
• Communication network issues (e.g., CAN bus problems)
• Damaged or corroded pins in connectors

Common misdiagnosis for U1974 U1974: “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 U1974 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 and ground. Use a multimeter to check the power supply to the module.
• Test the Module: If possible, test the affected module to ensure it is functioning correctly. This may involve using specialized diagnostic tools or swapping the module with a known good one.
• Inspect the CAN Bus:
• If the vehicle uses a Controller Area Network (CAN) bus for communication, check the integrity of the CAN bus wiring.
• Look for shorts, opens, or high resistance in the CAN bus lines (usually CAN High and CAN Low).
• Check for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the communication between modules.
• Perform a Network Test: Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly.
• Reset the Modules: Sometimes, resetting the affected module(s) or performing a hard reset of the vehicle’s electrical system can clear temporary communication issues.
• Update Software/Firmware: Check if there are any software or firmware updates available for the vehicle’s modules. Sometimes, communication issues can be resolved with an update.
• 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. 1
• Professional Diagnosis: If the issue persists after performing these steps, it may be necessary to consult a professional technician or dealership for further diagnosis. By following these steps, you can systematically identify and resolve the underlying cause of the U1974 code.