U1168 – SCP (J1850) Invalid or Missing Data for Primary Id

The ODBII code U1168 SCP (J1850) Invalid or Missing Data for Primary Id indicates that the vehicle’s communication network is not receiving valid or expected data from a primary module, which may affect the operation of various systems.

The severity of ODBII code U1168 is moderate.

Common Causes For: U1167 U1167: “Module Communication Failure”

• 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 U1168 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• Software glitches or outdated firmware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 U1168 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. Other codes may provide more context or indicate related issues.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with 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 Modules:
• Identify the modules that communicate over the J1850 bus (e.g., PCM, BCM, ABS, etc.) and check their functionality.
• Use a scan tool to communicate with each module individually to see if they respond correctly.
• Inspect the SCP Bus:
• Use an oscilloscope or a multimeter to check the signal on the J1850 bus. Look for proper voltage levels and signal integrity.
• Check for short circuits or open circuits in the bus wiring.
• Check for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the communication on the J1850 bus.
• Clear Codes and Test Drive: After performing inspections and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Update or Reprogram Modules: In some cases, a software update or reprogramming of the affected modules may be necessary to resolve communication issues.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the specific make and model of the vehicle, as there may be known issues or fixes for the U1168 code.
• Seek Professional Help: If the issue persists after performing the above steps, consider seeking assistance from a qualified technician or automotive professional who has experience with OBD-II systems and communication protocols. By following these troubleshooting steps, you should be able to identify and resolve the underlying issue causing the U1168 code.