U1605 – Communication Bus Fault.

The ODBII code U1605 indicates a communication bus fault, typically signifying a problem with the data communication between various control modules in the vehicle.

The severity of ODBII code U1605 is moderate.

Common Causes For: U1604 refers to a communication issue between the engine control module (ECM) and the transmission control module (TCM).

• Faulty wiring or connectors in the communication bus.
• Malfunctioning control modules.
• Poor ground connections.
• Short circuits in the communication lines.
• Interference from aftermarket devices.
• Corroded or damaged pins in connectors.
• Software issues or bugs in the control modules.
• Low battery voltage or power supply issues.

Common misdiagnosis for U1605 Communication Bus Fault.

• Faulty Engine Control Module (ECM)
• Defective Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Bad ground connections
• Faulty sensors or actuators
• Corrupted software or firmware in modules
• Battery or charging system problems
• Incorrectly installed aftermarket accessories or modifications

Common Troubleshooting Steps

The OBD-II code U1605 indicates a communication bus fault, which typically means there is an issue with the communication between the vehicle’s control modules. 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 Wiring and Connectors:
• Visually inspect the wiring and connectors related to the communication bus (CAN bus). Look for any signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors at the ECM (Engine Control Module) and other control modules.
• Test the Communication Bus:
• Use a multimeter or an oscilloscope to check the voltage levels on the CAN bus wires. The typical voltage should be around 2.5V when the bus is idle.
• Check for short circuits or open circuits in the communication lines.
• Check for Ground Issues: Ensure that all control modules have a good ground connection. A poor ground can lead to communication issues.
• Inspect Modules:
• If possible, check the functionality of the control modules involved in the communication. A faulty module can disrupt communication.
• If you suspect a specific module, you may need to replace or reprogram it.
• Look for Interference:
• Check for any aftermarket devices or modifications that may interfere with the communication bus, such as alarms, remote starters, or stereo systems.
• Perform a Network Test: Some advanced scan tools can perform a network test to identify which module is not communicating properly.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Consult Service Manual: If the issue persists, refer to the vehicle’s service manual for specific diagnostic procedures related to the U1605 code.
• Seek Professional Help: If you are unable to resolve the issue, it may be best to consult a professional mechanic or technician who has experience with your specific vehicle make and model. By following these steps, you should be able to identify and resolve the underlying issue causing the U1605 communication bus fault.