U1446 – Control Module Communication Bus Off.

The ODBII code U1446 indicates a communication issue where a control module is not able to communicate properly on the vehicle’s communication bus, often due to a fault in the module or wiring.

The severity of ODBII code U1446 is moderate to severe.

Common Causes For: U1445 Manufacturer Specific” code, which typically indicates an issue related to communication between modules in the vehicle’s network.

• 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
• Low battery voltage or power supply issues
• Interference from aftermarket devices
• Faulty sensors or actuators on the bus

Common misdiagnosis for U1446 Control Module Communication Bus Off.

• Faulty ABS module
• Defective engine control module (ECM)
• Malfunctioning transmission control module (TCM)
• Bad wiring or connectors
• Faulty body control module (BCM)
• Incorrectly diagnosed sensor issues
• Battery or charging system problems
• Communication issues with other modules
• Software or firmware issues in control modules
• Grounding issues in the electrical system

Common Troubleshooting Steps

The OBD-II code U1446 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 factors, including wiring issues, module failures, or problems with the communication bus itself. Here are some common troubleshooting steps to diagnose and resolve the U1446 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. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors for the modules involved in the communication bus.
• Check Power and Ground: Verify that the affected control module has proper power and ground. Use a multimeter to check voltage at the module’s power supply pins and ensure that ground connections are solid.
• Test the Communication Bus: Use a scan tool to monitor the communication on the bus. Check for any irregularities in data transmission.
• If possible, use an oscilloscope to analyze the signal on the communication lines (CAN, LIN, etc.) to ensure they are functioning correctly.
• Inspect Control Modules: If a specific module is identified as the source of the problem, consider testing or replacing that module.
• Ensure that the module is compatible with the vehicle and has the latest firmware or software updates.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for short circuits or open circuits in the wiring harness associated with the communication bus.
• Look for any signs of wear or damage that could cause a break in the circuit.
• Clear Codes and Test Drive: After performing any repairs or adjustments, clear the trouble codes using the OBD-II scanner.
• 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 U1446 code for your specific vehicle make and model. Manufacturers may have known issues and recommended fixes.
• Seek Professional Help: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues.Conclusion Troubleshooting OBD-II code U1446 involves a systematic approach to identify and resolve communication issues within the vehicle’s control modules. By following these steps, you can often pinpoint the problem and take appropriate action to fix it.