U2918 – Vehicle Communication Bus Malfunction

The ODBII code U2918 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U2918 is generally considered moderate.

Common Causes For: U2917 Lost Communication with the Steering Angle Sensor.

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corrupted software or firmware in the modules
• Poor ground connections
• Interference from aftermarket devices
• Damaged or shorted communication lines
• Low battery voltage or power supply issues
• Faulty or incompatible OBD-II scanner or tool

Common misdiagnosis for U2918 Vehicle Communication Bus Malfunction

• Faulty Engine Control Module (ECM)
• Defective Body Control Module (BCM)
• Bad wiring or connectors
• Malfunctioning sensors
• Issues with the powertrain control module (PCM)
• Battery or charging system problems
• Incorrectly diagnosed transmission issues
• Faulty diagnostic tools or software errors

Common Troubleshooting Steps

The OBD-II code U2918 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, which can affect the overall functionality of systems that rely on this communication. 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 modules that are part of the communication network.
• Check for Short Circuits:
• Use a multimeter to check for short circuits in the wiring. Ensure that the communication lines are not shorted to ground or to each other.
• Test the Modules:
• If possible, test the individual modules on the communication bus to ensure they are functioning correctly. This may involve using specialized diagnostic tools or software.
• Inspect the CAN Bus Termination Resistors:
• Ensure that the CAN bus has the correct termination resistors in place. Typically, there should be a 120-ohm resistor at each end of the bus. If these resistors are missing or faulty, it can cause communication issues.
• Check for Interference:
• Look for any aftermarket devices or modifications that may be interfering with the communication bus. This includes things like alarm systems, stereo systems, or other electronic accessories.
• Battery and Ground Connections:
• Ensure that the vehicle’s battery is in good condition and that all ground connections are secure. Poor power or ground can lead to communication issues.
• Update or Reprogram Modules:
• In some cases, a software update or reprogramming of the affected modules may be necessary. Check with the manufacturer for any available updates.
• Scan Tool Communication:
• Verify that your OBD-II scanner is functioning properly and can communicate with the vehicle. Sometimes, the issue may be with the scanner itself.
• Consult Technical Service Bulletins (TSBs):
• Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on known issues related to communication bus malfunctions. 1
• Professional Diagnosis:
• If the issue persists after performing these steps, it may be necessary to consult a professional technician who has experience with the specific vehicle make and model. They may have access to advanced diagnostic tools and resources. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2918 code.