2022-2024 Hyundai Tucson ISG System Not Restarting TSB

Hyundai has issued Technical Service Bulletin (TSB) 23-FL-007H to address potential issues with the Idle Stop and Go (ISG) system in 2022-2024 Hyundai Tucson (NX4/NX4a) vehicles. This bulletin outlines a procedure to update the software for both the Transmission Control Module (TCM) and the Engine Control Module (ECM).

The primary goal of this update is to enhance the operation of the ISG system. Owners might experience a situation where their Hyundai Tucson ISG not restarting after the system has engaged, necessitating a manual restart. This condition is attributed to a temporary lack of intake manifold pressure recovery.

Symptoms

Owners may observe that their vehicle does not restart automatically after the Idle Stop and Go (ISG) system has activated. This requires the driver to manually restart the engine. This symptom indicates a potential problem with the ISG system's logic and its ability to recover intake manifold pressure efficiently, leading to the Hyundai Tucson ISG not restarting.

Important Warnings for Owners

• Battery Voltage: If your vehicle's battery voltage is below 12 volts, a warning message such as "Warning! lower Battery Voltage. BATTERY VOLTAGE: 11.7" may appear on the GDS (Global Diagnostic System) screen during the update process. If this occurs, you must run the vehicle for at least 20 minutes to ensure adequate battery charge before reattempting the update.
• TCU Update Applicability: The Transmission Control Unit (TCU) software updates (Event 1032 and Event 1034) are specifically for certain 2022MY vehicles only.

Software Updates for ISG Logic Improvement

The TSB details four specific software update events for improving the ISG logic, addressing the Hyundai Tucson ISG not restarting issue:

• Event 1031 (Engine): ECU software improvement for NX4 Theta III 2.5GDI engines in VINs starting with “KMH”. This update applies to 2022-2024 model year vehicles.
• Event 1032 (TCU): TCU software improvement for NX4 Theta III 2.5GDI engines in 2022MY vehicles with VINs starting with “KMH”.
• Event 1033 (Engine): ECU software improvement for NX4a Theta III 2.5GDI engines in VINs starting with “5NM”. This update applies to 2022-2024 model year vehicles.
• Event 1034 (TCU): TCU software improvement for NX4a Theta III 2.5GDI engines in 2022MY vehicles with VINs starting with “5NM”.

Repair Procedure Summary

The repair for the Hyundai Tucson ISG not restarting issue involves a software update performed by a Hyundai technician using the Global Diagnostic System (GDS). The general steps are as follows:

1. Perform ECU Update in Auto Mode: The technician must first perform the ECU update using the GDS in Auto Mode. Before proceeding, they will verify the ECU ROM ID to ensure the correct software is applied. For additional tablet-based Mobile GDS ECU update information, technicians are advised to refer to TSB 15-GI-001. Note that TCU updates (Event 1032 and 1034) are applicable only to certain 2022MY vehicles.
2. Document Completion: After the update, a screenshot of the