U1191 – SCP (J1850) Invalid or Missing Data for Primary Id

The ODBII code U1191 SCP (J1850) indicates that there is invalid or missing data for the primary identifier in the vehicle’s communication network, often related to issues with data transmission between modules.

The severity of ODBII code U1191 SCP (J1850) Invalid or Missing Data for Primary Id is moderate.

Common Causes For: U1190 U1190: “Module Communication Failure”

• Faulty or damaged wiring/connectors
• Malfunctioning or disconnected modules
• Communication network issues
• Low battery voltage
• Corrupted software or firmware in modules
• Interference from aftermarket devices
• Poor ground connections

Common misdiagnosis for U1191 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty PCM (Powertrain Control Module)
• Bad wiring or connectors
• Faulty data bus communication
• Incorrectly configured aftermarket accessories
• Defective sensors
• Battery or charging system issues
• Software glitches or updates needed
• Grounding issues

Common Troubleshooting Steps

The OBD-II code U1191 indicates an issue with the SCP (Serial Communication Protocol) related to the J1850 communication bus, specifically indicating that there is invalid or missing data for the primary identifier. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Sometimes, multiple codes can provide more context for the issue.
• Inspect Wiring and Connectors:
• Check the wiring and connectors related to the J1850 communication bus. Look for any signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors at the PCM (Powertrain Control Module) and any other modules that communicate over the J1850 bus.
• Verify Power and Ground:
• Ensure that the modules involved in the communication have proper power and ground connections. Use a multimeter to check voltage and ground continuity.
• Check for Short Circuits:
• Inspect the wiring for any short circuits or open circuits that could affect communication. This includes checking for shorts to ground or to other wires.
• Test the Modules:
• If possible, test the modules involved in the communication. This may involve using a scan tool to check for communication with each module on the bus.
• If a specific module is not responding, it may need to be replaced.
• Look for Interference:
• Check for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarms, stereo systems, or other electronic devices.
• Check for Software Updates:
• Sometimes, software issues can cause communication problems. Check with the manufacturer for any available software updates for the vehicle’s modules.
• Perform a Network Test:
• Use a scan tool capable of performing a network test to check the integrity of the communication bus. This can help identify if there are any issues with the bus itself.
• Clear Codes and Test Drive:
• After performing the above checks 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 issued guidance on common issues related to the U1191 code. If the problem persists after following these steps, it may be necessary to consult a professional technician or a dealership for further diagnosis.