U1121 – Lost Communication with Object 1.

The ODBII code U1121 indicates a loss of communication with a specific module or component in the vehicle, referred to as “Object 1,” which may affect various systems or functions.

The severity of ODBII code U1121 is generally considered moderate.

Common Causes For: U1120 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty wiring or connectors
• Failed control module
• Corroded or damaged connectors
• Poor ground connection
• Intermittent electrical issues
• Software or firmware issues
• Faulty sensors or actuators
• Communication network issues (e.g., CAN bus problems)

Common misdiagnosis for U1121 Lost Communication with Object 1.

• Faulty wiring or connectors
• Defective control module
• Software issues or updates needed
• Sensor malfunctions
• Power supply problems
• Grounding issues
• Intermittent communication faults
• Incorrectly configured aftermarket accessories

Common Troubleshooting Steps

The OBD-II code U1121 indicates a “Lost Communication with Object 1.” This code typically relates to a communication issue between the vehicle’s control modules, often involving the CAN (Controller Area Network) bus. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide context and help identify the root cause of the communication issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the affected module (Object 1). Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the CAN bus wiring, as it can be sensitive to damage.
• Check for Short Circuits or Open Circuits:
• Use a multimeter to test for continuity in the wiring. Look for any short circuits or open circuits that could be causing communication issues.
• Verify Power and Ground:
• Ensure that the affected module has proper power and ground connections. Use a multimeter to check voltage and ground integrity.
• Inspect the Affected Module:
• If the wiring and connections are intact, the issue may lie with the module itself. Check for any signs of physical damage or water intrusion.
• If possible, test the module in another vehicle or replace it with a known good module to see if the problem persists.
• Check for Interference:
• Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication network. This includes alarms, stereo systems, or other electronic devices.
• Scan for Communication Issues:
• Use a professional-grade scan tool to perform a network scan. This can help identify which module is not communicating properly and may provide more detailed information about the communication network.
• Reset the Codes:
• After performing checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs):
• Check for any manufacturer-specific TSBs related to U1121 or communication issues. There may be known fixes or recalls that apply to your vehicle.
• Seek Professional Help:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics and diagnostics. By following these steps, you can systematically diagnose and potentially resolve the U1121 code and its underlying communication issues.