U1900 – CAN Communication Bus Fault

The ODBII code U1900 indicates a fault in the CAN (Controller Area Network) communication bus, suggesting a communication issue between modules in the vehicle’s network.

The severity of ODBII code U1900 CAN Communication Bus Fault is generally considered moderate to severe.

Common Causes For: U1899 U1899: “Module Communication Failure”

• Faulty CAN bus wiring or connectors
• Short circuit in the CAN bus
• Open circuit in the CAN bus
• Faulty control module
• Poor ground connections
• Interference from other electrical components
• Corroded or damaged connectors
• Software issues or bugs in the control module
• Low battery voltage or power supply issues
• Faulty termination resistors

Common misdiagnosis for U1900 CAN Communication Bus Fault

• Faulty Engine Control Module (ECM)
• Faulty Transmission Control Module (TCM)
• Bad wiring or connectors
• Faulty Body Control Module (BCM)
• Defective sensors
• Battery or charging system issues
• Faulty CAN bus termination resistors
• Software or firmware issues in modules
• Grounding issues
• Intermittent electrical connections

Common Troubleshooting Steps

The OBD-II code U1900 indicates a CAN (Controller Area Network) communication bus fault. This code typically suggests that there is a problem with the communication between various modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve the U1900 code:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context about the issue.
• Inspect the Wiring and Connectors: **Visual Inspection: Look for damaged, frayed, or corroded wiring and connectors related to the CAN bus.
• **Connector Integrity: Ensure that all connectors are securely attached and free of corrosion.
• Test the CAN Bus: **Multimeter Test: Use a multimeter to check the voltage levels on the CAN High (CAN H) and CAN Low (CAN L) wires. The typical voltage levels should be around 2.5V when idle.
• **Scope Test: If available, use an oscilloscope to check the signal integrity on the CAN bus. Look for clean square wave signals.
• Check for Short Circuits: Inspect the CAN bus wiring for any short circuits to ground or to other wires. This can cause communication failures.
• Inspect Modules: **Module Functionality: Check if any modules on the CAN bus are malfunctioning. A faulty module can disrupt communication.
• **Power and Ground: Ensure that all modules have proper power and ground connections.
• Look for Intermittent Issues: Sometimes, the issue may be intermittent. Pay attention to when the code appears (e.g., during specific driving conditions or after certain actions).
• Check for Software Updates: Verify if there are any software updates available for the vehicle’s modules. Sometimes, manufacturers release updates to fix communication issues.
• Clear Codes and Test Drive: After performing inspections and repairs, clear the codes and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U1900 code for your specific vehicle make and model. Manufacturers may have specific recommendations for addressing this issue.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing CAN bus issues. By following these steps, you should be able to identify and resolve the underlying cause of the U1900 code.