Battery won't charge past 80% after l2 session + P1AA9(00) diag code...

IonicRabbit · 2025-10-05T13:00:46-0400

I plugged my 2024 IONIQ 5 Limited AWD in last night into my home level 2 charger and went to bed - as normal. Battery charged in about 3 hours from 50-90%. About two hours after charging ended, I received Bluelink push notification and email that stated:

Your 2024 IONIQ 5 (VIN#) has a battery issue. Charging is limited to 80%. Please schedule an appointment with Hyundai/Genesis dealership as soon as possible.

I plugged in my OBD-II dongle and received a code P1AA9(00). A search of these forums didn't turn up anything on that code, and the only thing I could find that was potentially related was about the Genesis GV-60's from https://dot.report/dtc/P1AA9. Zero search results had anything to do with the IONIQ 5.

The dot report site stated:

GENESIS: Certain gv60 (jw1 ev) vehicles may exhibit a condition where a cell voltage variation becomes active after charging. The battery management system (bms) software logic could cause an hv battery cell voltage to be misread under specific conditions resulting in a false-positive dtc, mil on, and 80% maximum hv battery charge limit. There is no other effect on the vehicle and all systems remain operational. With this update the charging logic is also improved for charging calibration and climate control functions in the genesis connect app. Regardless of whether the vehicle has an active dtc P1AA900 or not, follow the procedure in this tsb to update the software for the battery management system (bms).

I've attached a few screenshots from the OBD read outs.

My question: Has anyone else encountered this before?

IonicRabbit · 2025-10-05T13:28:26-0400

Did a little more digging, found a Hyundai TSB for the Kona EV model that specifically listed the P1AA9 DTC. Seems similar to what I experienced. Not excited to see that a BSA replacement may be needed...

https://static.nhtsa.gov/odi/tsbs/2023/MC-10244989-0001.pdf

Battery won't charge past 80% after l2 session + P1AA9(00) diag code...

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