U2849 – Control Module Communication Bus Off Error

The ODBII code U2849: Control Module Communication Bus Off Error indicates a communication failure between control modules in a vehicle, often due to a fault in the communication bus or a malfunctioning module.

The severity of ODBII code U2849 is moderate to high.

Common Causes For: U2848 U2848: Control Module Communication Bus Fault

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Communication bus interference
• Software issues or bugs
• Low battery voltage
• Corroded terminals
• Faulty or disconnected sensors

Common misdiagnosis for U2849 U2849: Control Module Communication Bus Off Error

• Faulty control module
• Wiring issues or shorts
• Poor ground connections
• Corrupted software or firmware in the control module
• Faulty connectors or terminals
• Battery or power supply issues
• Other communication bus errors (e.g., CAN bus issues)
• Intermittent faults in related modules

Common Troubleshooting Steps

The OBD-II code U2849 indicates a “Control Module Communication Bus Off Error.” This code typically suggests that there is a communication issue between the control modules in the vehicle, which can be caused by various factors. Here are some common troubleshooting steps to diagnose and resolve the issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Addressing related codes can help in diagnosing the root cause.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors associated with the control modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the communication bus wires (CAN bus) for any signs of wear or damage.
• Check Power and Ground: Ensure that the control modules have proper power and ground connections. Use a multimeter to verify voltage and ground continuity.
• Check the fuses related to the control modules and replace any that are blown.
• Test the Communication Bus: Use a scan tool to monitor the communication on the CAN bus. Check for any irregularities in the data being transmitted.
• If possible, use an oscilloscope to analyze the signal on the CAN bus for proper voltage levels and signal integrity.
• Disconnect Modules: Disconnect the control modules one at a time to see if the code clears or if communication is restored. This can help identify if a specific module is causing the issue.
• Check for Short Circuits: Inspect the wiring for any short circuits or grounding issues that could be affecting communication between modules.
• Update or Reprogram Modules: If the vehicle has had recent updates or repairs, ensure that all control modules are updated to the latest software version. Sometimes, reprogramming a module can resolve communication issues.
• Replace Faulty Modules: If a specific control module is identified as faulty (e.g., through testing or by elimination), consider replacing it.
• 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 communication errors.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues.Conclusion Troubleshooting OBD-II code U2849 requires a systematic approach to identify the root cause of the communication failure. By following these steps, you can narrow down the potential issues and work towards a resolution.