U1187 – OBD-II DTC

OBD-II DTC U1187 – SCP (J1850) Invalid or Missing Data for Primary Id

DTC U1187 meaning

DTC U1187 refers to a diagnostic trouble code indicating “Invalid or Missing Data for Primary Id” in vehicles equipped with the On-Board Diagnostics II (OBD-II) system. This code is specifically related to the SCP (Serial Communication Protocol) using the J1850 standard. It suggests that the vehicle’s control modules are unable to communicate properly, leading to a lack of essential data transmission.

DTC U1187 symptoms

Common symptoms associated with DTC U1187 may include:

• Illumination of the check engine light
• Erratic or non-functional vehicle features (e.g., radio, climate control)
• Loss of communication with certain modules
• Inconsistent performance of the vehicle

DTC U1187 causes

Several factors can lead to the occurrence of DTC U1187, including:

• Faulty wiring or connectors in the communication network
• Defective control modules
• Corrosion or damage to the connectors
• Software issues within the control modules
• Interference from aftermarket devices

DTC U1187 seriousness

The seriousness of DTC U1187 can vary. While it may not immediately affect the drivability of the vehicle, it can lead to more significant issues if left unaddressed. The inability to communicate with certain modules can result in malfunctioning systems, which may compromise safety and performance.

How to diagnose DTC U1187

To diagnose DTC U1187, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the code.
2. Check for any additional trouble codes that may provide more context.
3. Inspect the wiring and connectors related to the SCP network for damage or corrosion.
4. Test the affected control modules for proper operation.
5. Verify the integrity of the communication lines using a multimeter.
6. Check for software updates or reprogramming needs for the control modules.

How to fix DTC U1187 step-by-step instructions

To fix DTC U1187, follow these steps:

1. Repair or replace any damaged wiring or connectors found during diagnosis.
2. Replace any faulty control modules identified in the diagnostic process.
3. Clean any corroded connectors to ensure proper communication.
4. Update or reprogram control modules if necessary.
5. Clear the DTC using an OBD-II scanner and test drive the vehicle.
6. Recheck for the DTC to ensure it does not return.

How to erase DTC U1187

To erase DTC U1187, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn the ignition key to the “On” position without starting the engine.
3. Access the “Erase Codes” or “Clear DTCs” function on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the vehicle to ensure the code does not reappear.

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