U2835 – Vehicle Communication Bus Malfunction

The ODBII code U2835: Vehicle Communication Bus Malfunction indicates a problem with the communication network between various vehicle control modules, which may affect their ability to exchange data properly.

The severity of ODBII code U2835 is moderate.

Common Causes For: U2834 U2834: Vehicle Communication Network Malfunction

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corroded or damaged connectors
• Short circuits in the communication lines
• Open circuits in the communication lines
• Interference from aftermarket devices
• Software issues or bugs in the control modules
• Low battery voltage or power supply issues
• Grounding issues in the vehicle’s electrical system

Common misdiagnosis for U2835 U2835: Vehicle Communication Bus Malfunction

• Faulty ECM (Engine Control Module)
• Defective BCM (Body Control Module)
• Wiring issues or shorts in the communication lines
• Bad ground connections
• Malfunctioning sensors or actuators
• Issues with the CAN bus system
• Corrupted software or firmware in control modules
• Battery or power supply problems

Common Troubleshooting Steps

The OBD-II code U2835 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 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 CAN bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the modules that are part of the communication network.
• Test the CAN 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 bus is idle.
• Check for proper termination resistors (usually 120 ohms) at both ends of the CAN bus. If they are missing or faulty, it can cause communication issues.
• Check for Short Circuits: Inspect the CAN bus wiring for any short circuits to ground or to other wires. This can disrupt communication between modules.
• Examine Modules: Identify and test the modules that are part of the communication network. If a specific module is malfunctioning, it may cause the entire network to fail.
• If possible, try disconnecting non-essential modules one at a time to see if the code clears or communication is restored.
• Check Power and Ground: Ensure that all modules on the CAN bus have proper power and ground connections. A weak or intermittent power supply can lead to communication failures.
• 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.
• 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 Service Manual: Refer to the vehicle’s service manual for specific diagnostic procedures related to the CAN bus and any manufacturer-specific troubleshooting steps.
• Seek Professional Help: 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 make and model. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the U2835 code.