P1A90 on Hyundai: How to Diagnose & Fix
DC/DC Converter Input Voltage Sensor Fault (ICCU)
2 Hyundai models · 2 documented issues · 2 critical
P1A90 on Hyundai by model: symptoms, diagnosis and fix
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 January 2025 expansion 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 January 2025 follow-up campaign.
Sources for this issue (3)
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)
P1A90 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1A90 mean on a Hyundai?
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. On Hyundai it is documented across 2 models: Ioniq 5, Ioniq 6.
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 on a Hyundai?
Repair costs vary widely with the root cause and Hyundai model; each issue on this page carries its own estimate where one is published.
Looking for P1A90 on a different make?
View P1A90 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.