U1143 – SCP (J1850) Invalid or Missing Data for Primary Id

The ODBII code U1143 SCP (J1850) indicates that there is invalid or missing data for the primary identifier in the vehicle’s communication network, which may affect the proper functioning of certain systems.

The severity of ODBII code U1143 SCP (J1850) Invalid or Missing Data for Primary Id is moderate.

Common Causes For: U1142 U1142: “Module Communication Failure”

• Faulty or damaged wiring/connectors
• Malfunctioning or disconnected sensors
• Issues with the vehicle’s communication network
• Faulty PCM (Powertrain Control Module)
• Corrupted or outdated software/firmware
• Poor ground connections
• Interference from aftermarket devices or modifications
• Low battery voltage or power supply issues

Common misdiagnosis for U1143 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty vehicle speed sensor
• Malfunctioning engine control module (ECM)
• Wiring issues or short circuits
• Faulty communication network (CAN bus)
• Incorrectly configured or faulty aftermarket accessories
• Defective or corroded connectors
• Issues with the body control module (BCM)

Common Troubleshooting Steps

When dealing with OBD-II code U1143, which indicates “Invalid or Missing Data for Primary ID” in the SCP (J1850) communication protocol, there are several common troubleshooting steps you can take 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. Sometimes, related codes can provide more context for the issue.
• Inspect the Wiring and Connectors: **Visual Inspection: Look for damaged, frayed, or corroded wiring and connectors related to the SCP bus.
• **Connector Integrity: Ensure that all connectors are securely attached and free of corrosion.
• Test the SCP Bus: **Bus Voltage: Use a multimeter to check the voltage on the SCP bus. It should typically be around 2.5V to 2.7V when the vehicle is on.
• **Signal Integrity: Use an oscilloscope to check for proper signal waveforms on the SCP bus. Look for noise or irregularities.
• Check for Short Circuits: Inspect the wiring for any short circuits to ground or to other wires that could be affecting the communication.
• Inspect Modules: **Module Functionality: Ensure that all modules on the SCP bus are functioning correctly. A malfunctioning module can disrupt communication.
• **Reprogram or Replace Modules: If a specific module is identified as faulty, consider reprogramming or replacing it.
• Check for Software Updates: Verify if there are any software updates available for the vehicle’s control modules. Sometimes, manufacturers release updates to fix communication issues.
• Clear Codes and Test Drive: After performing inspections and repairs, clear the trouble codes 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 specific make and model of the vehicle. Manufacturers may have documented solutions for common issues.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing SCP communication issues.
• Documentation and History: Review the vehicle’s history for any previous repairs or modifications that could have affected the SCP communication. By following these steps, you can systematically identify and address the root cause of the U1143 code. Always ensure safety precautions are taken when working on a vehicle’s electrical system.