U2928 – Vehicle Communication Bus Malfunction

The ODBII code U2928 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U2928 is generally considered moderate to severe.

Common Causes For: U2927 Vehicle Communication Bus Malfunction

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corrupted software or firmware in control modules
• Poor ground connections
• Interference from aftermarket devices
• Damaged or shorted communication lines
• Low battery voltage or power supply issues
• Faulty or damaged OBD-II port

Common misdiagnosis for U2928 Vehicle Communication Bus Malfunction

• Faulty Engine Control Module (ECM)
• Defective Body Control Module (BCM)
• Bad wiring or connectors
• Malfunctioning sensors
• Issues with the powertrain control module (PCM)
• Incorrectly diagnosed transmission problems
• Battery or charging system issues
• Faulty diagnostic tools or software errors

Common Troubleshooting Steps

The OBD-II code U2928 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various control modules in the vehicle. 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 additional trouble codes. Sometimes, related codes can provide more context for the problem.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the communication bus (CAN bus). Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the control modules, as well as any junction points in the wiring harness.
• Test the Communication Bus:
• Use a multimeter or an oscilloscope to check the voltage levels on the CAN bus wires. The typical voltage levels should be around 2.5V to 3.5V when the vehicle is on.
• Check for short circuits or open circuits in the communication lines.
• Check Control Modules:
• Ensure that all control modules are functioning properly. A malfunctioning module can disrupt communication on the bus.
• If possible, perform a software update on the control modules, as outdated software can sometimes cause communication issues.
• Inspect for Interference:
• Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication systems, such as alarms, remote starters, or audio systems.
• Check Battery and Ground Connections:
• Ensure that the vehicle’s battery is in good condition and that all ground connections are secure. Poor power supply or grounding can lead to communication issues.
• Perform a Network Test:
• Some advanced scan tools can perform a network test to check the integrity of the communication bus. This can help identify which module may be causing the issue.
• Clear Codes and Test Drive:
• After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs):
• Check for any manufacturer-specific TSBs related to U2928 or communication issues. There may be known fixes or recalls that apply to your vehicle.
• Seek Professional Help:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2928 code.