2025-2026 Hyundai Tucson DCU Software Update TSB 25-01-061H

Hyundai has released Technical Service Bulletin (TSB) 25-01-061H, also known as Service Campaign TDFC, to address a potential software issue affecting the Data Communication Unit (DCU) in certain 2025-2026 Hyundai Tucson (NX4A) vehicles. This bulletin provides instructions for a software update designed to correct a specific Hyundai Tucson DCU software error.

The Hyundai Tucson DCU software error is related to an internal timer initialization logic that was not properly implemented. This oversight can lead to the DCU module shutting down telematics services after the vehicle has been in service for one year.

Symptoms

Owners of affected 2025-2026 Hyundai Tucson vehicles may experience a complete loss of telematics services. This means features like Blue Link services, emergency assistance, and other connected car functionalities may become unavailable after approximately one year of vehicle ownership.

What's Being Addressed

The core issue is a software error within the Data Communication Unit (DCU), specifically concerning its internal timer initialization logic. This prevents the DCU from functioning correctly long-term, leading to the shutdown of telematics services. The TSB 25-01-061H aims to resolve this by updating the DCU software to ensure proper timer initialization.

Important Warnings for Owners and Technicians

Hyundai has provided several critical advisories regarding this service campaign:

• Dealers are required to perform this service campaign on all affected vehicles before customer retail delivery. It must also be completed whenever an affected vehicle is in the shop for any maintenance or repair.
• The software update may be available as an Over-the-Air (OTA) update for customers with active Blue Link Services subscriptions.
• Before performing the software update, ensure the vehicle's battery charge is above 11.0 Volts and the diagnostic tablet's battery charge is above 30% to prevent update failure.
• During the update process, do NOT leave the headlamp switch in auto mode, turn OFF all other lamps and accessories.
• Do NOT disconnect any cables connected to the vehicle or scan tool during the update.
• Do NOT start the engine during the update.
• Do NOT turn OFF the ignition switch during the update.
• If the update fails, do NOT immediately retry. Instead, remove the power connector from the in-cabin fuse box for at least 5 seconds, or disconnect the negative (-) 12V battery terminal for at least 5 seconds. Then reassemble and retry the update.
• If the ECU update fails in Auto Mode, it can be performed in Manual Mode using a specific password.

Diagnosis and Repair Procedure Summary

To identify open campaigns, technicians should access the “Vehicle Information” screen via WebDCS. The repair involves updating the DCU software using specialized tools.

1. Preparation: Ensure the vehicle's battery and the diagnostic tablet are sufficiently charged. Turn off all lamps and accessories, and ensure the ignition switch is in the ON position.
2. Tool Connection: Connect the Ethernet Communication Interface (ECI) DLC cable to the OBD connector. Then, connect the VCI DLC cable to the ECI. Select the appropriate tablet cable (Type C, 5-pin) and connect it to the ECI, then connect the cable to the tablet PC.
3. Software Update: Perform the ECU update using the GDS system in Auto Mode. If the update fails in Auto Mode, it should be attempted in Manual Mode.
4. ROM ID Verification: After the update, verify the new ROM ID by scanning the DCU system and comparing it to the latest ROM ID (120.NA.012054.012054).
5. Control Unit Reset: Once the ECU update shows 100% completion, cycle the ignition OFF for at least 10-30 seconds to reset the control unit.
6. OTA Initialization: The Over-the-Air (OTA) initialization should perform automatically. If it fails, it must be completed manually under S/W Management > CCU_CCNF - Central Communication Unit (CCNF) > OTA Initialization.
7. Documentation: Take a screenshot of the ECU Update