P1A90: How to Diagnose & Fix — DC/DC Converter Input Voltage Sensor Fault (ICCU)
3 vehicles · 2 makes
How to diagnose and fix P1A90: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Genesis GV70 · 2023–2025
The Integrated Charging Control Unit (ICCU) charges the 12-volt battery. Certain electrical loads can make its internal MOSFET fail and open the ICCU fuse, so the 12V battery stops charging. The car then enters a fail-safe mode with warnings; if it is driven until the 12V battery is depleted, it loses all motive power. Certain 2023-2025 Electrified GV70 built at Hyundai Motor Manufacturing Alabama January 25, 2023 to November 9, 2024 (Genesis 025G). It includes 2023-2024 Electrified GV70s previously involved in Genesis recall 021G. Gasoline GV70s are not included. Eligibility is by VIN.
How to Fix
Have a Genesis retailer check the VIN for recall 24V868 (025G). The retailer updates the ICCU software and replaces the ICCU and its fuse if necessary, free of charge. Genesis has also extended coverage for ICCU and ICCU-fuse replacement on 2023-2025 Electrified GV70 to 15 years or 180,000 miles from original delivery (extension Z06G). Per the report, warning lights, a chime, on-screen messages and reduced power may appear over roughly 20-40 minutes of fail-safe driving. Observe the vehicle warnings and stop safely if drive power is reduced. Do not rely on an illustrated countdown or keep driving to exhaust a stated warning interval. High-voltage work requires an EV-qualified retailer.
Sources for this issue (3)
- Hyundai Part 573 report 24V-868 (Hyundai 272 / Genesis 025G), December 17, 2024 amendmentrecall
- Genesis extended warranty notification Z06G (ICCU and ICCU fuse, 15 years/180,000 miles)manufacturer
- Genesis service campaign 907G retailer best practice (TSB 23-01-069G-1), ICCU inspection for DTC P1A9096tsb
Hyundai Ioniq 6 · 2023–2025
NHTSA recall 24V-868 covers 28,932 model-year 2023-2025 Ioniq 6 vehicles. Electrical load conditions can cause a MOSFET inside the Integrated Charging Control Unit (ICCU) to fail and open the ICCU fuse, preventing the ICCU from charging the 12-volt battery. The vehicle then enters a fail-safe mode that gradually reduces motive power; if the 12-volt battery is fully depleted, all motive power can be lost.
Common Symptoms
- Dashboard warning lights or warning messages
- Audible warning chime
- Gradual reduction in motive power or speed
- Loss of motive power after full 12-volt battery depletion
How to Fix
Check the VIN for NHTSA recall 24V-868 (Hyundai 272), which expands and replaces the earlier recall. Hyundai dealers update ICCU software and replace the ICCU assembly and associated fuse if necessary, free of charge. Vehicles repaired under the earlier campaign still need the updated remedy.
Sources for this issue (1)
Hyundai Ioniq 5 · 2022–2024
The Integrated Charging Control Unit (ICCU), which houses the DC-to-DC converter that keeps the 12V battery charged from the high-voltage pack, can suffer overvoltage and thermal overload that blows its internal 12V-feed fuse. When it fails the car may refuse to DC fast charge, charge slowly, drop into reduced-power 'turtle mode' on the highway, or lose all motive power and need a tow. NHTSA recall 24V-204 (March 2024, ~99K vehicles) was followed by a November 2024 expansion, recall 24V-868, covering ~145K vehicles after failures recurred on remedied cars.
Common Symptoms
- Sudden loss of drive power / 'turtle mode' warning while driving
- Repeated dead 12V battery / car won't power on or boot
- Vehicle won't DC fast charge or charges far slower than rated
- Loud popping/bang from front during charging followed by warning lights
- Car stranded and requires a tow out of limp-home mode
How to Fix
Covered by NHTSA recall: dealers check for DTC P1A9096 — if absent they apply an ICCU software update to reduce overvoltage stress; if present they replace the ICCU and its fuse, flush/refill coolant, and install updated software, free of charge. Owners reporting recurrence after the software-only fix have driven ongoing litigation and the November 2024 expansion recall 24V-868 (Hyundai 272), which replaces 24V-204.
Sources for this issue (4)
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Frequently asked questions
What does P1A90 mean?
P1A90 stands for "DC/DC Converter Input Voltage Sensor Fault (ICCU)." Stored by the Integrated Charging Control Unit, which bundles the on-board charger, DC-DC converter, and vehicle-to-load export hardware into one box. The module reports an implausible or out-of-range input-voltage sensor reading on the DC-DC converter stage, meaning the ICCU can no longer reliably step the high-voltage pack down to charge the 12-volt battery. Hyundai/Kia/Genesis service documentation carries it as the sub-coded fault P1A9096 in the ICCU inspection, fuse-replacement, and software-update campaign. Once the ICCU stops feeding 12 volts, the 12V battery drains and the vehicle progressively loses accessories, then drive power.
What are the most common causes of P1A90?
The most common causes of P1A90 are: ICCU internal failure (DC-DC converter stage) on E-GMP platform vehicles, Blown ICCU input fuse following an ICCU fault event, Outdated ICCU control software (addressed by manufacturer software update), 12-volt battery repeatedly deep-discharged by a failing ICCU. The specific cause varies by vehicle.
How much does it cost to fix P1A90?
Repair costs vary widely depending on the root cause and vehicle.
Which vehicles are affected by P1A90?
Au7o has documented P1A90 across 3 vehicle models from 2 manufacturers: Genesis, Hyundai.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.