U1091 – OBD-II DTC

OBD-II DTC U1091 – SCP (J1850) Invalid or Missing Data for Non-Legislated Diagnostics

DTC U1091 meaning

DTC U1091 refers to a diagnostic trouble code indicating “Invalid or Missing Data for Non-Legislated Diagnostics” in vehicles using the SCP (J1850) communication protocol. This code typically arises when the vehicle’s control modules are unable to communicate properly, leading to a lack of expected data from one or more modules. It is often associated with issues in the communication network rather than a specific component failure.

DTC U1091 symptoms

Common symptoms associated with DTC U1091 may include:

• Illumination of the check engine light
• Loss of communication with certain vehicle systems
• Erratic or non-functional dashboard gauges
• Inconsistent performance of vehicle features that rely on electronic control modules

DTC U1091 causes

Several factors can lead to the occurrence of DTC U1091, including:

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

DTC U1091 seriousness

The seriousness of DTC U1091 can vary based on the symptoms and the specific vehicle. While it may not indicate an immediate threat to safety, it can lead to significant issues with vehicle performance and functionality. Ignoring this code may result in further complications, including the failure of critical systems that rely on proper communication between modules.

How to diagnose DTC U1091

To diagnose DTC U1091, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the U1091 code.
2. Check for any additional trouble codes that may provide more context.
3. Inspect the vehicle’s wiring and connectors for damage or corrosion.
4. Test the affected control modules for proper operation.
5. Verify the integrity of the communication network using a multimeter.
6. Check for software updates or reprogramming needs for the control modules.

How to fix DTC U1091 step-by-step instructions

To fix DTC U1091, follow these step-by-step instructions:

1. Address any wiring or connector issues found during diagnosis.
2. Replace any faulty control modules identified in the diagnostic process.
3. Clean or repair corroded connectors to ensure proper communication.
4. Update or reprogram control modules if software issues are detected.
5. Disconnect any aftermarket devices that may interfere with the communication network.
6. Clear the DTC using an OBD-II scanner and test drive the vehicle to ensure the code does not return.

How to erase DTC U1091

To erase DTC U1091, 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.

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