U2972 – Vehicle Communication Bus Malfunction

The ODBII code U2972 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U2972 is generally considered moderate to severe.

Common Causes For: U2971 U2971: “Vehicle Communication Bus Malfunction”

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corrupted software or firmware in control modules
• Poor ground connections
• Short circuits or open circuits in the communication lines
• Interference from aftermarket devices
• Damaged or defective OBD-II port
• Low battery voltage or power supply issues

Common misdiagnosis for U2972 Vehicle Communication Bus Malfunction

• Faulty Engine Control Module (ECM)
• Defective Body Control Module (BCM)
• Bad wiring or connectors
• Malfunctioning Transmission Control Module (TCM)
• Issues with the CAN bus system
• Incorrectly diagnosed sensor failures
• Power supply issues to modules
• Software or firmware problems in control modules

Common Troubleshooting Steps

The OBD-II code U2972 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 Controller Area Network (CAN) bus. 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 the 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 at the ECM (Engine Control Module) and other modules that communicate over the bus.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for continuity in the CAN bus wiring. Look for any short circuits or open circuits that could disrupt communication.
• Check for shorts to ground or power in the CAN bus wires.
• Test the Modules: If possible, test the individual modules (like the ECM, BCM, ABS, etc.) for proper operation. A malfunctioning module can disrupt communication on the bus.
• If you have access to a scan tool that can communicate with individual modules, check if they respond correctly.
• Inspect the CAN Bus Termination Resistors: Ensure that the CAN bus has the correct termination resistors (typically 120 ohms) at both ends of the bus. A missing or faulty resistor can cause communication issues.
• Check for Interference: Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication systems, such as alarms, remote starters, or audio systems.
• Update or Reprogram Modules: In some cases, a software update or reprogramming of the affected modules may resolve communication issues. Check with the manufacturer for any available updates.
• Clear Codes and Test Drive: After performing any repairs or adjustments, 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 U2972 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations for this issue.
• 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. They may have specialized tools and knowledge to address complex communication issues. By following these steps, you can systematically diagnose and potentially resolve the U2972 code. Always refer to the vehicle’s service manual for specific procedures and specifications related to your vehicle.