U1929 – Module Communication Failure

The ODBII code U1929 indicates a “Module Communication Failure,” meaning there is a problem with communication between vehicle modules, often due to a fault in the wiring, connectors, or the modules themselves.

The severity of ODBII code U1929 is moderate.

Common Causes For: U1928 U1928: “Module Communication Failure”

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Poor ground connections
• Corroded or damaged pins in connectors
• Intermittent communication issues
• Software or firmware issues in modules
• Low battery voltage or power supply issues
• Faulty CAN bus communication
• Electrical interference or noise
• Aftermarket modifications or installations affecting communication

Common misdiagnosis for U1929 U1929: “Module Communication Failure”

• Faulty wiring or connectors
• Defective control module
• Software issues or updates needed
• Power supply problems
• Grounding issues
• Intermittent communication issues
• Other module failures
• Incorrectly configured or programmed modules

Common Troubleshooting Steps

The OBD-II code U1929 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: Start by scanning the vehicle for any other diagnostic trouble codes (DTCs). Sometimes, U1929 may be accompanied by other codes that can provide additional context for the issue.
• 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 the ground connections, as poor grounding can lead to communication issues.
• Check Module Power Supply: Ensure that the affected module(s) are receiving the proper voltage and ground. Use a multimeter to check the power supply to the module. If the module is not powered correctly, it may not communicate.
• Verify Module Functionality: If possible, test the affected module(s) to ensure they are functioning correctly. This may involve using a scan tool to access the module and check for any internal faults.
• Inspect the CAN Bus: U1929 is often related to issues with the Controller Area Network (CAN) bus. Check the CAN bus wiring for shorts, opens, or interference. You can use an oscilloscope to monitor the CAN signals for proper voltage levels and signal integrity.
• Check for Software Updates: Sometimes, communication issues can be resolved with a software update. Check with the vehicle manufacturer or a dealership to see if there are any available updates for the affected modules.
• 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.
• Inspect for Environmental Factors: Ensure that there are no environmental factors affecting the modules, such as moisture or extreme temperatures, which could lead to communication failures.
• 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 common issues related to module communication.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its electronic systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1929 code.