U1906 – CAN Communication Malfunction

The ODBII code U1906 indicates a malfunction in the Controller Area Network (CAN) communication system, which affects the ability of various vehicle modules to communicate with each other.

The severity of ODBII code U1906 is moderate.

Common Causes For: U1905 U1905: “BCM Communication Failure”

• Faulty CAN bus wiring or connectors
• Defective CAN bus module
• Short circuit in the CAN bus
• Open circuit in the CAN bus
• Interference from other electronic devices
• Faulty or incompatible aftermarket accessories
• Poor ground connections
• Corroded or damaged terminals
• Software or firmware issues in the control modules
• Low battery voltage or power supply issues

Common misdiagnosis for U1906 U1906: “CAN Communication Malfunction”

• Faulty CAN bus wiring
• Defective control modules
• Poor ground connections
• Corroded connectors
• Intermittent electrical issues
• Software glitches in modules
• Faulty sensors
• Battery or charging system problems

Common Troubleshooting Steps

The OBD-II code U1906 indicates a “CAN Communication Malfunction.” This code typically points to issues with the Controller Area Network (CAN) communication system in a vehicle, which is essential for various modules to communicate with each other. Here are some common troubleshooting steps to diagnose and resolve the U1906 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 context and help identify the root cause of the communication issue.
• Inspect the Wiring and Connectors: Visually inspect the wiring and connectors related to the CAN bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors at the Engine Control Module (ECM), Body Control Module (BCM), and any other modules that communicate over the CAN bus.
• Test the CAN Bus Voltage: Use a multimeter to measure the voltage on the CAN High (CAN H) and CAN Low (CAN L) wires. The typical voltage levels should be around 2.5V when the bus is idle.
• If the voltage levels are significantly off, there may be a short circuit or an open circuit in the wiring.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for continuity in the CAN bus wiring. Look for any shorts to ground or power, as well as open circuits that could disrupt communication.
• Inspect Modules for Faults: Check the individual modules on the CAN bus for faults. A malfunctioning module can disrupt communication for the entire network.
• If possible, perform a module reset or reprogramming to see if that resolves the issue.
• Look for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the CAN bus communication. This includes alarm systems, stereo systems, or other electronic devices.
• Check for Software Updates: Verify if there are any software updates available for the vehicle’s modules. Sometimes, manufacturers release updates to fix known communication issues.
• Perform a Network Test: If you have access to a professional-grade scan tool, perform a network test to check the status of the CAN bus and the modules connected to it.
• 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 a Professional: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics and CAN bus systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the U1906 code.