U1246 – SCP (J1850) Invalid or Missing Data for Primary Id

The ODBII code U1246 SCP (J1850) indicates that there is invalid or missing data for the primary identifier in the communication network, often related to issues with the vehicle’s communication system or modules.

The severity of ODBII code U1246 is moderate.

Common Causes For: U1245 SCP (J1850) Invalid or Missing Data for Interior Environment

• Faulty or damaged wiring/connectors
• Malfunctioning or disconnected sensors
• Issues with the vehicle’s communication network
• Defective control modules
• Low battery voltage or poor power supply
• Corrupted software or firmware in control modules
• Interference from aftermarket devices or modifications

Common misdiagnosis for U1246 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty O2 sensor
• Bad fuel injectors
• Malfunctioning mass air flow sensor
• Defective engine control module (ECM)
• Wiring issues or shorts in the data bus
• Faulty battery or poor ground connections
• Incorrectly installed aftermarket accessories
• Issues with the instrument cluster
• Problems with the transmission control module (TCM)

Common Troubleshooting Steps

The OBD-II code U1246 indicates an issue with the SCP (Serial Communication Protocol) on the J1850 bus, specifically related to invalid or missing data for the primary ID. This can be caused by various factors, including communication issues between modules, wiring problems, or faulty components. Here are some common troubleshooting steps to diagnose and resolve the issue:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Addressing other codes may resolve the U1246 code.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors related to the J1850 bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the modules that communicate over the J1850 bus.
• Check Battery Voltage: Ensure that the vehicle’s battery is fully charged and that the voltage is within the normal range (typically 12.4 to 12.6 volts). Low voltage can cause communication issues.
• Test the Communication Bus: Use a multimeter or an oscilloscope to check the voltage levels on the J1850 bus. You should see a specific voltage pattern when the vehicle is running.
• If you have access to a scan tool that can monitor live data, check for communication between modules.
• Inspect Modules: Identify the modules that communicate over the J1850 bus (e.g., PCM, BCM, ABS, etc.). Check for any signs of failure or malfunction.
• If possible, perform a module reset or reprogramming if the module is suspected to be faulty.
• Check for Ground Issues: Ensure that all ground connections related to the modules are secure and free of corrosion. Poor grounding can lead to communication problems.
• Look for Intermittent Issues: Sometimes, the issue may be intermittent. Pay attention to when the code appears (e.g., during specific driving conditions) and check for any patterns.
• Perform a Network Test: If available, use a professional scan tool to perform a network test. This can help identify which module is not communicating properly.
• Check for Software Updates: Check if there are any software updates available for the vehicle’s modules. Sometimes, manufacturers release updates to fix communication issues.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the U1246 code for your specific vehicle make and model. Manufacturers may have specific recommendations for addressing this issue.1
• Replace Faulty Components: If a specific module is identified as faulty, consider replacing it. Ensure that the replacement module is compatible with your vehicle.1
• Clear Codes and Test Drive: After performing repairs, clear the codes and take the vehicle for a test drive to see if the code returns.Conclusion If the issue persists after following these steps, it may be necessary to consult a professional technician or a dealership for further diagnosis. They may have access to more advanced diagnostic tools and resources to pinpoint the problem accurately.