U2936 – Control Module Communication Bus Fault

The ODBII code U2936 indicates a communication fault on the control module communication bus, suggesting that there is a problem with the data exchange between control modules in the vehicle.

The severity of ODBII code U2936 is generally considered moderate to severe.

Common Causes For: U2935 U2935: “Vehicle Communication Bus Malfunction”

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Corroded terminals
• Short circuits in the communication bus
• Intermittent electrical connections
• Software issues or bugs in the control module
• Faulty or incompatible aftermarket components
• Low battery voltage or power supply issues
• Communication bus interference

Common misdiagnosis for U2936 U2936: Control Module Communication Bus Fault

• Faulty control module
• Wiring issues or shorts
• Corroded connectors
• Battery or power supply problems
• Software or firmware issues
• Other communication bus faults (e.g., CAN bus issues)
• Grounding problems
• Intermittent faults in related systems

Common Troubleshooting Steps

The OBD-II code U2936 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 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 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 for Short Circuits: Use a multimeter to check for short circuits in the communication lines. Ensure that the wires are not shorted to ground or to each other.
• Test Control Modules: If possible, test the control modules involved in the communication bus. This may involve checking for proper operation or replacing modules if they are found to be faulty.
• Inspect Ground Connections: Ensure that all ground connections for the control modules are secure and free of corrosion. Poor grounding can lead to communication issues.
• Check for Interference: Look for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarms, stereo systems, or other electronic devices.
• Scan for Communication Issues: Use a professional-grade scan tool to monitor the communication between modules. This can help identify which module is not communicating properly.
• Perform a Network Test: Some advanced scan tools can perform a network test to check the integrity of the communication bus. This can help pinpoint the issue.
• Update Software/Firmware: Check if there are any software or firmware updates available for the control modules. Sometimes, updating the software can resolve communication issues.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.1
• Consult Service Manual: Refer to the vehicle’s service manual for specific diagnostic procedures related to the communication bus and control modules.1
• 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 issue causing the U2936 code.