U1103 – OBD-II DTC

OBD-II DTC U1103 – SCP (J1850) Invalid or Missing Data for Primary Id

DTC U1103 meaning

DTC U1103 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 communication standard. It suggests that the vehicle’s control module is unable to receive valid data from another module, which may affect various systems within the vehicle.

DTC U1103 symptoms

Common symptoms associated with DTC U1103 may include:

• Illumination of the check engine light
• Loss of communication with certain vehicle modules
• Erratic behavior of vehicle systems (e.g., ABS, traction control)
• Inconsistent readings on the dashboard
• Possible performance issues, such as reduced power or acceleration

DTC U1103 causes

Several factors can lead to the occurrence of DTC U1103, including:

• Faulty wiring or connectors in the communication network
• Defective control module(s) that are not sending or receiving data
• Corrupted software or firmware in the vehicle’s modules
• Interference from aftermarket devices or modifications
• Low battery voltage or poor electrical connections

DTC U1103 seriousness

The seriousness of DTC U1103 can vary depending on the specific vehicle and the systems affected. While it may not cause immediate safety concerns, it can lead to:

• Increased difficulty in diagnosing other related issues
• Potential failure of critical systems that rely on communication
• Decreased vehicle performance and drivability

How to diagnose DTC U1103

To diagnose DTC U1103, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC U1103.
2. Check for any additional trouble codes that may provide more context.
3. Inspect the vehicle’s wiring and connectors related to the communication network.
4. Test the affected control modules for proper operation.
5. Verify the vehicle’s battery voltage and electrical connections.
6. Check for software updates or reprogramming needs for the control modules.

How to fix DTC U1103 step-by-step instructions

To fix DTC U1103, follow these steps:

1. Inspect and repair any damaged wiring or connectors in the communication network.
2. Replace any faulty control modules identified during diagnosis.
3. Update or reprogram the software in the affected modules if necessary.
4. Clear any aftermarket devices that may interfere with communication.
5. Ensure the vehicle’s battery is fully charged and connections are secure.
6. Re-scan the vehicle to confirm that DTC U1103 has been resolved.

How to erase DTC U1103

To erase DTC U1103 from the vehicle’s memory, 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. Navigate to the “Erase Codes” or “Clear DTCs” option on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the vehicle to check if the code reappears.

Recommended tools for OBD-II diagnostics

Explore our expert picks: The Best OBD2 Scanners for 2025

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.