U2820 – Control Module Communication Bus Fault

The ODBII code U2820: Control Module Communication Bus Fault indicates a communication issue between control modules in a vehicle, suggesting that one or more modules are not properly communicating over the vehicle’s data bus.

The severity of ODBII code U2820 is moderate to severe.

Common Causes For: U2819 U2819: “Vehicle Communication Bus Malfunction”

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Short circuits in the communication bus
• Open circuits in the communication bus
• Corroded connectors
• Interference from aftermarket devices
• Software issues or bugs in the control module
• Low battery voltage or power supply issues
• Faulty communication protocols or settings

Common misdiagnosis for U2820 U2820: Control Module Communication Bus Fault

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or power supply problems
• Intermittent connection issues
• Other communication bus faults (e.g., CAN bus issues)

Common Troubleshooting Steps

The OBD-II code U2820 indicates a “Control Module Communication Bus Fault.” This code typically points to a communication issue between various control modules in the vehicle. 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. Sometimes, multiple codes can provide more context about the issue.
• Inspect Wiring and Connectors: **Visual Inspection: Check the wiring harnesses and connectors associated with the control modules for any signs of damage, corrosion, or loose connections.
• **Connector Pins: Ensure that the pins in the connectors are not bent, corroded, or pushed back.
• Check Power and Ground: Verify that the affected control modules are receiving proper power and ground. Use a multimeter to check voltage and ground continuity.
• Test the Communication Bus: Use a scan tool to monitor the communication on the CAN bus (Controller Area Network) or other communication protocols used in the vehicle.
• Check for any abnormal signals or interruptions in communication.
• Inspect Control Modules: If a specific control module is suspected, check its functionality. This may involve testing the module or replacing it if necessary.
• Ensure that the module is properly programmed and configured for the vehicle.
• Check for Short Circuits: Inspect the wiring for any short circuits that may be causing communication issues. This can include shorts to ground or power.
• Look for Intermittent Issues: Sometimes, communication faults can be intermittent. Pay attention to when the code appears (e.g., during specific driving conditions) and check for any patterns.
• Update Software/Firmware: Check if there are any software or firmware updates available for the control modules. Sometimes, manufacturers release updates to fix communication issues.
• Clear Codes and Test Drive: After performing any repairs or inspections, clear the codes 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 documented solutions for known issues.1
• 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. By following these steps, you should be able to identify and resolve the underlying cause of the U2820 code.