U1145 – SCP (J1850) Invalid or Missing Data for Primary Id

The ODBII code U1145 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 U1145 SCP (J1850) Invalid or Missing Data for Primary Id is moderate.

Common Causes For: U1144 U1144: “Module Communication Failure”

• Faulty or damaged wiring/connectors
• Malfunctioning control module
• Poor ground connections
• Communication issues between modules
• Corrupted data or software glitches
• Faulty sensors or actuators
• Interference from aftermarket devices
• Low battery voltage or power supply issues

Common misdiagnosis for U1145 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 damaged diagnostic tools
• Issues with other control modules (e.g., transmission control module)
• Battery or power supply problems
• Corrupted software or firmware in the vehicle’s systems

Common Troubleshooting Steps

The OBD-II code U1145 indicates that there is an issue with the communication on the SCP (Serial Communication Protocol) bus, specifically related to the J1850 protocol. This code typically means that the vehicle’s control module is not receiving valid data from a primary module, which can lead to various performance issues. Here are some common troubleshooting steps to diagnose and resolve the U1145 code:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Addressing other codes may resolve the U1145 issue.
• Inspect the Wiring and Connectors: **Visual Inspection: Look for damaged, corroded, or loose connectors and wiring related to the modules on the SCP bus.
• **Repair or Replace: Fix any damaged wiring or connectors that you find.
• Check the Battery and Ground Connections: Ensure that the battery is fully charged and that all ground connections are clean and secure. Poor ground connections can lead to communication issues.
• Test the Modules: **Module Functionality: Verify that the primary module (often the PCM or another control module) is functioning correctly. If possible, use a scan tool to check for communication with the module.
• **Module Replacement: If a specific module is found to be faulty, consider replacing it.
• Inspect the SCP Bus: **Bus Integrity: Check the integrity of the SCP bus. Look for shorts, opens, or resistance issues in the wiring.
• **Signal Testing: Use an oscilloscope or multimeter to test the signal on the SCP bus for proper voltage levels and waveforms.
• Check for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the SCP communication.
• Perform a Network Test: If available, use a professional scan tool to perform a network test to check the communication between modules on the SCP bus.
• Clear Codes and Test Drive: After performing 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 U1145 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations.
• Seek Professional Help: If the issue persists after performing the above steps, consider seeking help from a qualified technician or automotive professional who has experience with OBD-II systems and the specific vehicle. By following these troubleshooting steps, you should be able to identify and resolve the underlying issue causing the U1145 code.