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U code network Medium severity

U1091 SCP (J1850) Invalid or Missing Data for Non-Legislated Diagnostics

The OBD2 code U1091 SCP (J1850) indicates that there is invalid or missing data from a communication network, specifically related to non-legislated diagnostics, which may affect the vehicle's performance or diagnostics

Definition

The OBD2 code U1091 SCP (J1850) indicates that there is invalid or missing data from a communication network, specifically related to non-legislated diagnostics, which may affect the vehicle's performance or diagnostics

Common causes

  • Faulty or damaged wiring/connectors
  • Malfunctioning control modules
  • Poor ground connections
  • Communication issues between modules
  • Corrupted software or firmware in the control module
  • Interference from aftermarket devices
  • Low battery voltage or power supply issues
  • Faulty sensors or actuators related to the communication network

Common misdiagnoses

  • Faulty wiring or connectors
  • Defective control modules
  • Sensor malfunctions
  • Communication issues between modules
  • Battery or power supply problems
  • Software or firmware issues
  • Incorrectly installed aftermarket accessories

Troubleshooting steps

  1. 1. 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 U1091 code

  2. 2. Inspect the Wiring and Connectors

    Visually inspect the wiring and connectors related to the SCP bus. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the connectors for the modules that communicate over the SCP bus

  4. 4. Check the Battery and Ground Connections

    Ensure that the vehicle's battery is in good condition and fully charged

  5. 5. Check the ground connections for the modules involved in the SCP communication. Poor ground connections can lead to communication issues

  6. 6. Test the SCP Bus

    Use a multimeter or an oscilloscope to test the SCP bus for proper voltage levels and signal integrity

  7. 7. Check for short circuits or open circuits in the SCP wiring

  8. 8. Inspect Modules

    Identify the modules that communicate over the SCP bus (e.g., Instrument Cluster, ABS Module, etc.)

  9. 9. Check for any signs of failure or malfunction in these modules. If a specific module is suspected, it may need to be tested or replaced

  10. 10. Perform a Network Test

    If available, use a scan tool that can perform a network test to check the communication between modules

  11. 11. This can help identify if a specific module is not responding or if there is a communication fault

  12. 12. Clear Codes and Test Drive

    After performing inspections and repairs, clear the trouble codes using the OBD-II scanner

  13. 13. Take the vehicle for a test drive to see if the code returns. Monitor the vehicle's performance and any warning lights

  14. 14. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the U1091 code for your specific vehicle make and model. Manufacturers may have issued guidance on common issues and fixes

  15. 15. Seek Professional Help

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or automotive technician who has experience with OBD-II diagnostics and the specific vehicle make and model. By following these troubleshooting steps, you can systematically identify and address the underlying issues causing the U1091 code