U2845 – Vehicle Communication Bus Malfunction

The ODBII code U2845 indicates a malfunction in the vehicle communication bus, which affects the ability of various electronic control units (ECUs) to communicate with each other.

The severity of ODBII code U2845 is moderate.

Common Causes For: U2843 U2843: Control Module Communication Bus Fault

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corroded or damaged terminals
• Poor ground connections
• Interference from aftermarket devices
• Software issues or bugs in the control modules
• Low battery voltage or power supply issues
• Faulty OBD-II port or connectors

Common misdiagnosis for U2845 U2845: “Vehicle Communication Bus Malfunction”

• Faulty ECM (Engine Control Module)
• Defective BCM (Body Control Module)
• Wiring issues or shorts in the communication bus
• Bad ground connections
• Faulty sensors or actuators
• Incorrectly programmed modules
• Battery or charging system problems
• Corroded connectors or terminals

Common Troubleshooting Steps

The OBD-II code U2845 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 Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the communication bus (CAN bus). Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the control modules, as well as any junction points in the wiring harness.
• Test the Communication Bus:
• Use a multimeter or an oscilloscope to check the voltage levels on the communication lines. The CAN bus should typically have a voltage of around 2.5V when idle.
• Check for proper termination resistors (usually 120 ohms) at both ends of the CAN bus. If they are missing or faulty, it can cause communication issues.
• Check for Short Circuits:
• Inspect the wiring for any short circuits to ground or to other wires. A short can disrupt communication between modules.
• Inspect Control Modules:
• If the wiring and connectors appear to be in good condition, the issue may lie with one of the control modules. Check for any signs of damage or failure in the modules that communicate over the bus.
• If possible, perform a module reset or reprogramming, as software issues can sometimes cause communication failures.
• Look for Interference:
• Check for any aftermarket devices or modifications that may interfere with the vehicle’s communication systems. This includes alarm systems, stereo systems, or other electronic devices.
• Perform a Network Test:
• Some advanced scan tools can perform a network test to check the status of each module on the bus. This can help identify which module is not responding.
• Check Battery and Ground Connections:
• Ensure that the vehicle’s battery is in good condition and that all ground connections are secure. Poor power supply or grounding can lead to communication issues.
• Consult Technical Service Bulletins (TSBs):
• Check for any TSBs related to your vehicle make and model that may address known issues with the communication bus.
• Seek Professional Help:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with vehicle communication systems. By following these troubleshooting steps, you should be able to identify and resolve the underlying cause of the U2845 code.