U1263 – Communication Bus Off.

The ODBII code U1263 indicates a communication issue where the vehicle’s communication bus is offline or not functioning properly, often due to a fault in the network or a module failure.

The severity of ODBII code U1263 is moderate to severe.

Common Causes For: U1262 SCP (J1850) Communication Bus Fault

• Faulty or damaged wiring in the communication bus.
• Defective control modules.
• Poor connections or corroded terminals.
• Short circuits in the communication lines.
• Interference from aftermarket devices.
• Software issues or bugs in the control modules.
• Low battery voltage or power supply issues.

Common misdiagnosis for U1263 Communication Bus Off.

• Faulty ECM (Engine Control Module)
• Bad wiring or connectors
• Defective sensors
• Battery issues
• Faulty ABS module
• Incorrectly programmed modules
• Communication issues with other control modules

Common Troubleshooting Steps

The OBD-II code U1263 indicates a “Communication Bus Off” condition, which typically means that there is a problem with the communication between the vehicle’s control modules. 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 U1263 code:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide additional context for the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors related to the communication bus (CAN bus, LIN bus, etc.) for any signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors at the control modules and any junction points.
• Test the Communication Bus:
• Use a multimeter or an oscilloscope to check the voltage levels and signal integrity on the communication bus wires.
• Ensure that the bus is receiving the correct voltage and that the signals are within the expected range.
• Check for Short Circuits or Open Circuits:
• Use a multimeter to check for continuity in the communication bus wiring. Look for any short circuits or open circuits that could disrupt communication.
• Inspect Control Modules:
• Check the control modules involved in the communication bus for any signs of failure. This may include modules such as the Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM), etc.
• If possible, perform a reset or reprogramming of the affected modules.
• Look for Ground Issues:
• Ensure that all ground connections related to the control modules and communication bus are secure and free of corrosion.
• Check 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.
• Perform a Network Test:
• If available, use a scan tool that can perform a network test to check the status of the communication bus and identify any modules that are not responding.
• Clear Codes and Test Drive:
• After performing the above checks 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 Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures and wiring diagrams related to the communication bus. 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 automotive electronics and communication systems. By following these troubleshooting steps, you should be able to identify and resolve the underlying issue causing the U1263 code.