U2738 – Vehicle Communication Bus Malfunction

The ODBII code U2738 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U2738 is moderate.

Common Causes For: U2735 U2735: Control Module Communication Bus Fault

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corrupted software in the control 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 U2738 Vehicle Communication Bus Malfunction

• Faulty ECM (Engine Control Module)
• Defective BCM (Body Control Module)
• Wiring issues or shorts in the communication lines
• Faulty sensors or actuators
• Incorrectly diagnosed transmission issues
• Power supply problems to modules
• Software or firmware issues in control modules
• Corroded or loose connectors in the communication network

Common Troubleshooting Steps

The OBD-II code U2738 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, often related to the CAN (Controller Area Network) bus system. 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 related trouble codes. Addressing other codes may resolve the U2738 code.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harnesses and connectors associated with the CAN bus for any signs of damage, corrosion, or loose connections.
• **Repair or Replace: Repair any damaged wires or connectors as necessary.
• Check the CAN Bus Termination Resistors: Ensure that the termination resistors (typically 120 ohms) at both ends of the CAN bus are present and functioning correctly. A missing or faulty resistor can cause communication issues.
• Test the Modules: **Module Functionality: Check the functionality of the modules connected to the CAN bus. If one module is malfunctioning, it can disrupt communication.
• **Communication Test: Use a scan tool to check if all modules are communicating properly. If one module is not responding, it may need to be replaced.
• Inspect for Short Circuits or Open Circuits: Use a multimeter to check for short circuits or open circuits in the CAN bus wiring. This can help identify any faults in the wiring.
• Check for Interference: Look for any aftermarket devices or modifications that may be interfering with the CAN bus communication. This includes alarms, stereo systems, or other electronic devices.
• Update or Reprogram Modules: In some cases, updating or reprogramming the vehicle’s modules may resolve communication issues. Check with the manufacturer for any available updates.
• Clear Codes and Test Drive: After performing 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): Check for any TSBs related to the U2738 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis.Conclusion Troubleshooting a U2738 code can be complex due to the nature of vehicle communication systems. Following these steps systematically can help identify and resolve the underlying issue. Always refer to the vehicle’s service manual for specific guidance related to your make and model.