U1901 – CAN Communication Bus Fault.

The ODBII code U1901 indicates a fault in the CAN (Controller Area Network) communication bus, suggesting a problem with data transmission between modules in the vehicle’s network.

The severity of ODBII code U1901 CAN Communication Bus Fault is generally considered moderate to severe.

Common Causes For: U1900 U1900: “CAN Communication Bus Malfunction”

• 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 electrical components
• Faulty or incompatible aftermarket accessories
• Software or firmware issues in the control modules
• Low battery voltage or poor ground connections

Common misdiagnosis for U1901 CAN Communication Bus Fault.

• Faulty ABS module
• Defective engine control module (ECM)
• Malfunctioning body control module (BCM)
• Wiring issues or shorts in the CAN bus
• Faulty sensors connected to the CAN bus
• Bad ground connections
• Defective transmission control module (TCM)
• Issues with the instrument cluster
• Corroded connectors or terminals
• Battery or power supply problems

Common Troubleshooting Steps

The OBD-II code U1901 indicates a CAN (Controller Area Network) communication bus fault. This code typically suggests that there is a problem with the communication between the various modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve the U1901 code:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context or indicate which module is having issues.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harnesses and connectors related to the CAN bus for any signs of damage, corrosion, or loose connections.
• **Repair or Replace: Repair any damaged wires or connectors as necessary.
• Check the CAN Bus Termination Resistors: Ensure that the CAN bus has the correct termination resistors (typically 120 ohms) at both ends of the bus. A missing or faulty resistor can cause communication issues.
• Test the Modules: **Module Functionality: Check the functionality of the modules on the CAN bus. If one module is malfunctioning, it can disrupt communication.
• **Communication Test: Use a scan tool to see if you can communicate with all modules on the bus. If one module is unresponsive, it may need to be repaired or replaced.
• Check for Short Circuits: Use a multimeter to check for short circuits in the CAN bus wiring. A short can cause communication failures.
• Inspect the Battery and Ground Connections: Ensure that the vehicle’s battery is in good condition and that all ground connections are clean and secure. Poor power or ground can lead to communication issues.
• Look for Interference: Check for any aftermarket devices or modifications that may interfere with the CAN bus communication. This includes alarms, stereo systems, or other electronic devices.
• Perform a Network Test: If available, use a specialized CAN bus diagnostic tool to perform a network test. This can help identify issues with the bus itself.
• Clear Codes and Test Drive: After performing repairs, clear the trouble codes 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 troubleshooting procedures and wiring diagrams related to the CAN bus system.1
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these steps, you should be able to identify and resolve the underlying issue causing the U1901 code.