U2021 – Invalid /fault data received (Non SCP)

The ODBII code U2021 indicates that the vehicle’s control module has received invalid or faulty data from another module that is not using the SCP (Serial Communication Protocol).

The severity of OBDII code U2021 is generally considered moderate.

Common Causes For: U2020 U2020: Invalid Message Received from Control Module

• Faulty communication between modules
• Corrupted or damaged wiring harness
• Poor ground connections
• Malfunctioning control modules
• Software issues or bugs in the modules
• Interference from aftermarket devices
• Low battery voltage or power supply issues
• Faulty sensors or actuators
• Incorrectly configured or programmed modules
• Environmental factors affecting module performance

Common misdiagnosis for U2021 Invalid /fault data received (Non SCP)

• Faulty wiring or connectors
• Malfunctioning control modules
• Incorrectly programmed modules
• Communication network issues
• Sensor failures
• Software glitches
• Grounding issues
• Intermittent electrical faults

Common Troubleshooting Steps

When dealing with OBD-II code U2021, which indicates “Invalid/Fault Data Received (Non-SCP),” it typically points to a communication issue between modules in the vehicle’s network. Here are common troubleshooting steps to help 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. Addressing other codes may resolve the U2021 code.
• Inspect Wiring and Connectors: Examine the wiring and connectors associated with the affected modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to ground connections, as poor grounding can lead to communication issues.
• Check for Module Communication: Use a scan tool to check if all modules are communicating properly. If some modules are not responding, it may indicate a problem with those specific modules or their connections.
• Inspect the CAN Bus: If your vehicle uses a Controller Area Network (CAN) bus, check for issues with the bus itself. Look for shorts, opens, or other faults in the wiring.
• Use an oscilloscope or a CAN bus analyzer to monitor the bus signals for irregularities.
• Test the Affected Module: Identify which module is reporting the U2021 code. If possible, test the module to ensure it is functioning correctly.
• If the module is faulty, it may need to be repaired or replaced.
• 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 trouble codes using the scan tool 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 U2021 code for your specific vehicle make and model. Manufacturers may have documented known issues and solutions.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues.
• Document Findings: Keep a record of all findings, repairs, and tests performed. This documentation can be helpful for future reference or if further diagnosis is needed. By following these steps, you should be able to identify and resolve the underlying issue causing the U2021 code.