U1648 – Communication Network Malfunction

The ODBII code U1648 indicates a “Communication Network Malfunction,” which means there is a problem with the communication between various control modules in the vehicle’s network.

The severity of ODBII code U1648 is moderate.

Common Causes For: U1647 U1647: “BCM Communication Failure”

• Faulty wiring or connectors in the communication network.
• Malfunctioning control modules.
• Corrupted software or firmware in control modules.
• Poor ground connections.
• Interference from aftermarket devices.
• Low battery voltage or weak battery.
• Faulty or damaged CAN bus.

Common misdiagnosis for U1648 U1648: “Communication Network Malfunction”

• Faulty ABS module
• Defective engine control module (ECM)
• Bad wiring or connectors
• Malfunctioning body control module (BCM)
• Issues with the transmission control module (TCM)
• Faulty sensors (e.g., wheel speed sensors)
• Battery or charging system problems
• Incorrectly programmed modules
• Faulty diagnostic tools or software errors
• Communication issues with other modules

Common Troubleshooting Steps

The OBD-II code U1648 indicates a “Communication Network Malfunction.” This code typically points to issues with the vehicle’s communication network, which can affect various modules and systems. Here are some common troubleshooting steps to diagnose and resolve the issue:

• Check for Additional Codes:
• Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide context and help pinpoint the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors related to the communication network. Look for signs of damage, corrosion, or loose connections. Pay special attention to the CAN (Controller Area Network) bus wiring.
• Check for Short Circuits:
• Use a multimeter to check for short circuits in the communication lines. Ensure that there are no unintended connections between wires.
• Test the Modules:
• Identify the modules that are part of the communication network (e.g., engine control module, transmission control module, body control module). Check if they are functioning properly. You may need to perform a module reset or reprogramming if necessary.
• Inspect the CAN Bus:
• Use a scan tool that can read CAN bus data. Check for proper voltage levels and signal integrity on the CAN bus. The typical voltage levels should be around 2.5V when idle and should fluctuate when data is being transmitted.
• Check for Interference:
• Look for any aftermarket devices or modifications that may interfere with the communication network. This includes alarms, 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 battery voltage or ground issues can lead to communication problems.
• Perform a Network Test:
• Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly.
• Update Software/Firmware:
• Check if there are any software or firmware updates available for the vehicle’s modules. Sometimes, updating the software can resolve communication issues.
• Consult Technical Service Bulletins (TSBs):
• Look for any TSBs related to the U1648 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations for this code. 1
• Professional Diagnosis:
• 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. By following these steps, you should be able to identify and resolve the underlying cause of the U1648 code.