U2999 – is a generic communication error code that indicates a problem with the vehicle’s communication network.

The ODBII code U2999 indicates a generic communication error within the vehicle’s communication network, suggesting a problem with data transmission between modules.

The severity of ODBII code U2999 is generally considered moderate.

Common Causes For: U2998 Lost Communication with Vehicle Control Module.

• Faulty wiring or connectors in the communication network.
• Malfunctioning control modules.
• Corrupted software or firmware in a control module.
• Poor ground connections.
• Interference from aftermarket devices.
• Low battery voltage or weak battery.
• Faulty OBD-II port or connectors.

Common misdiagnosis for U2999 is a generic communication error code that indicates a problem with the vehicle’s communication network.

• Faulty ECM (Engine Control Module)
• Bad wiring or connectors
• Defective sensors
• Incorrectly installed aftermarket accessories
• Faulty TCM (Transmission Control Module)
• Issues with the CAN bus system
• Malfunctioning body control module (BCM)
• Battery or charging system problems
• Software or firmware issues
• Grounding problems

Common Troubleshooting Steps

When dealing with OBD-II code U2999, which indicates a generic communication error in the vehicle’s communication network, there are several common troubleshooting steps you can follow to diagnose and potentially resolve the issue. Here’s a structured approach:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. U2999 may be accompanied by other codes that can provide more context about the issue.
• Inspect the OBD-II Connector: Ensure that the OBD-II connector is clean and free of corrosion.
• Check for any loose or damaged pins in the connector.
• Examine Wiring and Connectors: Inspect the wiring harnesses related to the communication network (CAN bus, LIN bus, etc.) for any signs of damage, fraying, or corrosion.
• Look for any loose or disconnected connectors that may affect communication.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for continuity in the communication lines.
• Look for any short circuits or open circuits that could disrupt communication.
• Inspect Modules and Components: Identify and inspect the modules that are part of the communication network (e.g., Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM)).
• Ensure that all modules are functioning properly and are powered on.
• Test the Communication Network: Use a scan tool to monitor the communication between modules. Check if all modules are responding correctly.
• If possible, perform a network test to see if the communication lines are functioning as expected.
• Check for Software Updates: Verify if there are any software updates available for the vehicle’s modules. Sometimes, communication issues can be resolved with a software update.
• Inspect for Environmental Factors: Check for any environmental factors that may affect communication, such as water intrusion or excessive heat.
• Clear Codes and Test Drive: After performing inspections and repairs, clear the trouble codes using the OBD-II scanner.
• Take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on known communication issues.1
• Seek Professional Help: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication network issues. By following these steps, you can systematically identify and address the underlying cause of the U2999 code.