U1186 – SCP (J1850) Invalid or Missing Data for Primary Id

The ODBII code U1186 indicates that there is invalid or missing data for the primary identifier in the SCP (Service Communication Protocol) using the J1850 communication standard, which may affect communication between modules in the vehicle.

The severity of ODBII code U1186 is moderate.

Common Causes For: U1185 SCP (J1850) Invalid or Missing Data for Window Wiper / Washer

• Faulty or damaged wiring/connectors
• Malfunctioning control modules
• Poor ground connections
• Communication network issues
• Corrupted data signals
• Incompatible or faulty aftermarket devices
• Software glitches in the vehicle’s systems
• Low battery voltage or power supply issues

Common misdiagnosis for U1186 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty OBDII connector
• Bad ground connections
• Malfunctioning PCM (Powertrain Control Module)
• Corrupted data from other modules
• Wiring issues or shorts in the communication lines
• Faulty sensors or actuators
• Software glitches or outdated firmware
• Battery or power supply issues

Common Troubleshooting Steps

The OBD-II code U1186 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 onboard computer 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 U1186 code:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Addressing other codes may resolve the U1186 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 may be causing communication issues.
• 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 problems.
• Test the Modules: **Module Functionality: Verify that the modules on the SCP bus (such as the PCM, BCM, etc.) are functioning correctly. If a module is faulty, it may not communicate properly.
• **Reprogram or Replace: If a module is found to be defective, it may need to be reprogrammed or replaced.
• Inspect the SCP Bus: **Bus Integrity: Check the integrity of the SCP bus. Use a multimeter to measure the resistance and ensure there are no shorts or open circuits.
• **Signal Quality: Use an oscilloscope to check the signal quality on the bus. Look for any irregularities in the waveform.
• Check for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the SCP communication.
• Clear Codes and Test Drive: After performing the above 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 TSBs related to the U1186 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known 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 communication issues. By following these troubleshooting steps, you should be able to identify and resolve the underlying issue causing the U1186 code.