U1972 – Control Module Communication Bus Off.

The ODBII code U1972 indicates a communication issue where a control module is not able to communicate over the vehicle’s communication bus, often due to a fault in the module or wiring.

The severity of ODBII code U1972 is moderate to severe.

Common Causes For: U1970 Lost Communication with the Hybrid Powertrain Control Module (HPCM)”.

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Communication bus failure
• Short circuit in the communication lines
• Corroded connectors
• Software issues or bugs in the control module
• Interference from aftermarket devices or modifications

Common misdiagnosis for U1972 Control Module Communication Bus Off.

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or power supply issues
• Communication network problems
• Intermittent connection issues

Common Troubleshooting Steps

The OBD-II code U1972 indicates a communication issue on the control module communication bus, specifically that a module is “off” or not responding. This can be caused by various issues, including wiring problems, module failures, or issues with the communication bus itself. Here are some common troubleshooting steps to diagnose and resolve the U1972 code:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context about the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors related to the control modules on the communication bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check the Control Modules: Identify the control module that is reporting the U1972 code. This may require consulting the vehicle’s service manual.
• If possible, test the control module for proper operation. This may involve checking for power and ground at the module and ensuring it is functioning correctly.
• Test the Communication Bus: Use a multimeter or an oscilloscope to check the communication signals on the bus. Look for proper voltage levels and signal integrity.
• If you have access to a scan tool that can monitor live data, check for communication between modules.
• Check for Short Circuits or Open Circuits: Perform a continuity test on the communication lines to ensure there are no breaks or shorts in the wiring.
• Check for any shorts to ground or power that could affect communication.
• Inspect for Interference: Look for any aftermarket devices or modifications that may interfere with the communication bus, such as alarms, remote starters, or other electronic devices.
• Reset the Codes: After performing inspections 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 Technical Service Bulletins (TSBs): Check for any TSBs related to the U1972 code for your specific vehicle make and model. Manufacturers may have known issues and recommended fixes.
• Replace Faulty Components: If a specific control module is determined to be faulty after testing, it may need to be replaced. Ensure that any replacement module is properly programmed and configured for your vehicle.
• Seek Professional Help: If the issue persists after performing these steps, consider seeking assistance from a professional mechanic or dealership with experience in diagnosing communication issues. By following these troubleshooting steps, you should be able to identify and resolve the underlying issue causing the U1972 code.