U1628 – Vehicle Communication Bus Malfunction

The ODBII code U1628 indicates a malfunction in the vehicle communication bus, which affects the ability of various modules to communicate with each other.

The severity of ODBII code U1628 is moderate.

Common Causes For: U1627 U1627: “Vehicle Communication Bus Malfunction”

• Faulty OBD-II connector
• Damaged wiring or connectors in the communication bus
• Malfunctioning control modules
• Poor ground connections
• Corroded or loose terminals
• Software issues or bugs in the control modules
• Interference from aftermarket devices
• Low battery voltage or power supply issues
• Faulty CAN bus transceiver
• Issues with the vehicle’s body control module (BCM)

Common misdiagnosis for U1628 U1628: “Vehicle Communication Bus Malfunction”

• Faulty OBDII connector
• Bad ground connections
• Defective ECM (Engine Control Module)
• Faulty wiring or harness issues
• Malfunctioning CAN bus modules
• Corrupted software or firmware in control modules
• Battery or power supply issues
• Faulty sensors or actuators
• Intermittent communication issues
• Incorrectly installed aftermarket accessories

Common Troubleshooting Steps

The OBD-II code U1628 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various control modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve the issue:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Sometimes, other codes can provide context or lead to the root cause of the U1628 code.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the communication bus (CAN bus). Look for damaged, corroded, or loose connections.
• Pay special attention to the connectors on the Engine Control Module (ECM), Transmission Control Module (TCM), and any other modules that communicate over the bus.
• Check for Short Circuits:
• Use a multimeter to check for short circuits in the wiring. A short to ground or power can disrupt communication.
• Test the resistance of the communication lines to ensure they are within specifications.
• Test the Modules:
• If possible, test the individual control modules for proper operation. A malfunctioning module can cause communication issues.
• If you have access to a scan tool that can communicate with all modules, check if you can read data from each module.
• Inspect the CAN Bus Termination:
• Ensure that the CAN bus is properly terminated. There should be termination resistors at both ends of the bus. If these resistors are missing or faulty, it can lead to communication issues.
• Check for Interference:
• Look for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarm systems, stereo systems, or other electronic devices.
• Battery and Ground Connections:
• Ensure that the vehicle’s battery is in good condition and that all ground connections are secure. Poor power or ground can lead to communication failures.
• Update Software/Firmware:
• Check if there are any software updates available for the vehicle’s control modules. Sometimes, manufacturers release updates to fix known communication issues.
• 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 U1628 code returns.
• Consult Service Manual:
• If the issue persists, consult the vehicle’s service manual for specific diagnostic procedures related to the communication bus and the modules involved. 1
• Professional Diagnosis:
• If you are unable to resolve the issue, 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 cause of the U1628 code.