2023-2025 Kia Niro EV Power Converter and ICCU Failure Guide

Understanding the 2023-2025 Niro EV Power Converter (ICCU)

The component listed with part number 91958-AO020 is officially called a "Junction Box Assembly" by Kia, but it is functionally the Integrated Charging Control Unit (ICCU) for the 2023-2025 Niro EV. This unit is the brain behind charging the vehicle and keeping its 12V systems alive. Unlike the widespread ICCU issues seen in Kia's 800V platform vehicles (like the EV6), the Niro EV uses a different 400V part, which some owners suggest is more reliable, though not immune to problems. Failures in this unit are a significant concern because they can manifest in two distinct ways: an inability to charge via AC power, or a failure to maintain the 12V battery, which can leave you stranded.

Known Issues, Technical Service Bulletins (TSBs), and Recalls

While not as prevalent as on other Kia models, the 2023 Niro EV has a specific TSB related to ICCU failure.

• TSB ELE298 (September 2023): Kia issued this technical service bulletin for 2023 Niro EV models experiencing poor or no charging with a Level 1 or Level 2 charger. Symptoms include "Check electric vehicle system" or "Stop vehicle and check power supply" messages. The bulletin instructs technicians to check for specific Diagnostic Trouble Codes (DTCs) and, if present, to replace the ICCU assembly.
• Recall SC332 / NHTSA 25V-024: This recall is for a separate issue but is important for owners to be aware of. It concerns the floor wiring assembly under the manual front passenger seat, which can become damaged. This recall affects 2023-2025 Niro EV, HEV, and PHEV models.
• Drive Shaft Recall: Some 2023-2024 Niro EV models were recalled for improperly heat-treated drive shafts that could break and cause a loss of power.

Symptoms of a Failing Power Converter (ICCU)

A failing ICCU can present a range of symptoms depending on which internal component is failing.

1. Inability to Charge on Level 1 or Level 2: This is a primary symptom. The vehicle will charge successfully at a DC fast charging station but will show a "Charging unsuccessful" message or simply refuse to start charging when plugged into a home or public AC charger. 🎬 Watch this video to see these AC charging failures in action. This points to a failure in the On-Board Charger (OBC) portion of the ICCU.
2. Repeatedly Dead 12V Battery: If you find your 12V battery is constantly drained, even after replacing it, the DC-to-DC converter inside the ICCU is likely at fault. It is failing to recharge the 12V battery, which is essential for the car's computers, lights, and ability to start.
3. Warning Lights on the Dashboard: The most common messages include "Check Electric Vehicle System" and "Stop vehicle and check power supply". An audible "pop" or clunk from the vehicle when the failure occurs has also been reported in similar Kia/Hyundai models.
🎬 See a deep dive into ICCU failure causes and warning signs.
4. Vehicle-to-Load (V2L) Malfunctions: Problems with the V2L feature, such as it tripping with low-power devices, can sometimes be an early indicator of electrical system quirks, though not always a direct sign of ICCU failure.
🎬 Check out this helpful guide for troubleshooting V2L malfunctions.

Buying a Used 2023-2025 Niro EV Power Converter

Purchasing a used ICCU can save you a significant amount of money, but careful inspection and verification are essential for this complex and critical part.

Confirming Compatibility is Critical

What to Inspect on a Used Unit

• Physical Inspection: Check the aluminum casing for any cracks, deep gouges, or signs of impact.
• Connector Integrity: All electrical connectors should be clean, with no signs of corrosion, melting, or bent pins. The high-voltage connectors are particularly important.
• Signs of Tampering: Look for stripped screw heads or pry marks on the case seams. The unit should never have been opened.
• Source Vehicle Information: If possible, get the VIN of the donor vehicle. This allows you to check its history for accidents or electrical issues. Low-mileage units from collision-damaged vehicles are often a good source.

Why Choose Used OEM?

For a component this new and complex, there are virtually no new aftermarket options. A used OEM ICCU is a reliable choice because it was designed specifically for your vehicle's system. It avoids the risks of unproven third-party electronics and provides the same performance as the original part, often at a fraction of the dealer price.

Replacement Overview

• Installation Difficulty: 5/5 (Professional recommended)
• Estimated Time: 2.0 - 3.0 hours
• Programming Requirements: While some sources suggest it's a direct swap, it's wise to assume a dealer or specialized shop may need to perform a software update or configuration with a KDS diagnostic tool after installation to ensure all systems communicate correctly.

Power Converter Cost Comparison

Frequently Asked Questions (FAQ)