U2743 – Vehicle Communication Bus Malfunction

The ODBII code U2743 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U2743 is generally considered moderate to severe.

Common Causes For: U2742 Invalid Data Received from Vehicle Dynamics Control Module.

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

Common misdiagnosis for U2743 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)
• Battery or charging system problems
• Incorrectly installed aftermarket accessories
• Software or firmware issues in the vehicle’s modules

Common Troubleshooting Steps

The OBD-II code U2743 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, which can affect the overall functionality of the vehicle’s systems. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Additional 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: Examine the wiring and connectors associated with the communication bus. Look for signs of damage, corrosion, or loose connections. Pay special attention to the connectors for the modules involved in the communication.
• Check the Communication Bus: Use a multimeter or an oscilloscope to check the voltage levels and signal integrity on the communication bus (CAN bus, LIN bus, etc.). Ensure that the signals are within the expected range.
• Inspect Modules: Identify the modules that are part of the communication network. Check for any signs of failure or malfunction in these modules. If possible, perform a reset or reprogramming of the affected modules.
• Test Individual Modules: If you suspect a specific module is causing the issue, you can disconnect it from the communication bus and see if the code persists. If the code goes away, the module may be faulty.
• Check for Short Circuits: Inspect the wiring for any short circuits that may be causing interference in the communication bus. This can include checking for pinched wires or damaged insulation.
• 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.
• Software Updates: Check if there are any software updates available for the vehicle’s modules. Sometimes, manufacturers release updates to fix known communication issues.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• 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 common issues related to the communication bus. 1
• Professional Diagnosis: 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 communication systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2743 code.