U1262 – Communication Bus Off.

The ODBII code U1262 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 U1262 is moderate to severe.

Common Causes For: U1261 SCP (J1850) Single Ended (-) Circuit Failure

• Faulty or damaged wiring in the communication bus.
• Failed or malfunctioning control modules.
• Poor connections or corroded terminals in the wiring harness.
• Short circuits in the communication lines.
• Interference from aftermarket devices or modifications.
• Low battery voltage or weak battery.
• Faulty or damaged connectors.

Common misdiagnosis for U1262 Communication Bus Off.

• Faulty ECM (Engine Control Module)
• Bad wiring or connectors
• Defective sensors
• Powertrain Control Module (PCM) issues
• Battery or charging system problems
• Faulty CAN bus modules
• Grounding issues
• Communication errors with other modules

Common Troubleshooting Steps

The OBD-II code U1262 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 U1262 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 communication bus (CAN bus). Look for damaged, frayed, or corroded wires and loose connections.
• Pay special attention to the connectors on the modules involved in the communication.
• Check for Short Circuits:
• Use a multimeter to check for short circuits in the communication lines. Ensure that the CAN high and CAN low wires are not shorted to each other or to ground.
• Test the Communication Bus:
• Use a scan tool to monitor the communication on the bus. Check if other modules are responding correctly. If some modules are not communicating, it may indicate a problem with those specific modules.
• Inspect Modules:
• Check the control modules (e.g., Engine Control Module, Transmission Control Module) for any signs of damage or failure. If a specific module is not responding, it may need to be replaced.
• Check Power and Ground:
• Ensure that all control modules have proper power and ground connections. A lack of power or a poor ground can cause communication issues.
• Look for Interference:
• Check for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarms, stereo systems, or other electronic devices.
• 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 related to the communication bus and the U1262 code.
• Professional Diagnosis:
• If the issue persists after performing these steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues. By following these steps, you should be able to identify and resolve the underlying issue causing the U1262 code.