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ICCU Report Changelog

Substantive changes to the ICCU Report are logged here. Formatting, reorganization, and minor wording tweaks are not tracked — only changes that affect the information a reader would take away from the page.

May 19, 2026

Section 9 warranty table: Kia Canada extension added — 15 years / 290,000 km for 2022-2024 MY EV6, no cost to customers, with owner letters arriving in May 2026. Mirrors Kia America’s scope (EV6 only, no EV9) and matches the Hyundai/Genesis Canada mileage cap. The former separate Hyundai/Genesis Canada and Kia Canada rows were consolidated into a single “Canada (Hyundai / Genesis / Kia)” row since all three brands now share identical terms. Genesis Motor America row notes refreshed — GMA is now the last North American HMG brand without an extension.

May 12, 2026

Section 9 editor’s note: Added a paragraph after the Kia Niro EV TSB reference noting a reader-reported OBC-type failure on a 2025 Hyundai Tucson Plug-In Hybrid — dealer-confirmed OBC failure, fault code P1E01 (parent of the E-GMP OBC fault-code family), charging module part 36400-3DAJ6. Flagged as a single data point with notable diagnostic and failure-progression similarity to E-GMP OBC failures, though whether the root cause is the same is not yet clear. Thanks to Gary for the report.

May 11, 2026

Numerous minor corrections to refresh dates and update recall status in various regions. Section 9 warranty table expanded with the Kia America EV6 extension (April 22, 2026), the Hyundai Auto Canada extension covering Hyundai and Genesis vehicles (late April 2026), the addition of Kia EV6 / EV6 GT to the European extension, and explicit holdout rows for Kia Canada and Genesis Motor America.
Removed the “The repair cost problem” intro paragraphs that discussed the 10-year/100,000-mile EV System Warranty interpretation and the speculative no-mileage-cap recall coverage point. Both have been superseded by the warranty extensions now in the table.
Restored Section 8 heading to “The Unresolved Problem and Known Part Numbers” (TOC consistency). Subheading updated from “Q1 2026” to “Q2 2026.”
Refreshed time-stamp framing throughout the page: “as of mid-February 2026” / “as of February 2026” replaced with “as of May 2026” where appropriate. dateModified in the page’s structured data and the footer’s last-updated stamp were also refreshed.
Added a note to Section 9 about the April 2026 class action lawsuit (Young, et al., v. Hyundai Kefico, Inc.) and Hyundai corporate’s reported mention of an upcoming reliability improvement (per Torque News) and informal “more reliable” replacement part references in owner channels.
Split the affected-vehicles header into three tiers: documented ICCU failures, models that share the ICCU but aren’t native E-GMP, and newer E-GMP models with limited failure data to date.
Corrected BM2 installation caption: the negative lead is black, not yellow. Thanks to an eagle-eyed reader, TK, for the correction.
Section 1: Revised description of the ICCU housing — previously called a “fluid-cooled sealed aluminum box,” now described as a “fluid-cooled aluminum housing containing the electronic components.”
Section 2 attribution: The goingelectric.de teardown citation now explicitly names chris_11, who did the teardown work and identified the SCT1000N170 active-clamp MOSFET and the ~300 kHz switching frequency.
Section 6: Added “The humidity hypothesis” subsection presenting chris_11’s moisture-intrusion-via-breather theory, with links to the relevant German forum threads. The skeptical case is laid out in editor’s voice rather than as a bulleted argument: 60+ years of standard automotive humidity engineering, the OBC and LDC sharing the same housing/breather/air but only the LDC’s active clamp MOSFET preferentially failing, the missing geographic signal across humid vs. dry markets, and HMG’s recalls never targeting humidity. Closes with the “cabin occupants breathing” sub-argument acknowledged and an Auto Defogging tip for readers who buy that strand.
Section 9 mitigation table: Added row 11, “If you endorse the humidity theory: enable Auto Defogging,” tagged as theory-dependent and cross-linking to the Section 6 humidity discussion.

April 21, 2026

Updated Warranty section in Section 9 to include the US ICCU warranty extension — 15 years / 180,000 miles for affected Hyundai EVs, confirmed by Hyundai Motor America via Torque News. Updated the list of markets still without extensions (Australia; Kia/Genesis outside Korea).
Revised Section 8 (now “The Unresolved Problem and New Part Numbers”). Rewrote the opening subsection with Q1 2026 framing — focusing on Hyundai’s implicit claim that revised ICCUs “fix” the issue and why the continuing 2025/2026 model year failures undermine it. Added a note that this page has stopped maintaining a running list of ICCU part numbers; iccu.observer is the canonical community reference.
Extended the “What’s still missing” paragraph with a note that new data on new-part-number reliability may be slow to arrive, and committing to report failures of new-part-number ICCUs as they surface.
Dropped the yellow “What we still don’t know” callout, the “What we don’t know yet” bulleted list, and the Evidence Summary table from Section 8 — their content is covered by the revised “What’s still missing” paragraph.
Moved the Hyundai TSB 24-EV-004H / NHTSA MC-11006095-0001 service note from Section 8 to Section 9, placing it next to the paragraph about the @WrenchingRyan YouTube walkthrough where the DIY / salvage-ICCU discussion lives.
Tightened spacing in the Community Part Number Database callout.

April 16, 2026

Added paragraph to the Warranty section summarizing the 15-year ICCU warranty extensions announced in South Korea (November 2025), Europe, the UK, and Ireland (April 2026), with a link to the full news post.
Added link to @WrenchingRyan’s YouTube walkthrough of an Ioniq 5 ICCU replacement, with a hat-tip to the EV Odessey channel for the heads-up.

April 4, 2026

Added “ICCU Failed?” reporting section at bottom of page with links to: NHTSA safety complaint form, ICCU Incident Tracker database, and ICCU Observer Survey and Data page.
Added “ICCU FAILED?” banner between disclaimer and table of contents linking to the reporting section.

March 13, 2026

Added reader case study to Section 2 (OBC Failure Mode): 2022 Ioniq 5 SEL RWD, Feb 2022 build, 55,387 miles, DTC P1E011C. OBC failure with silent LDC degradation — 12V battery was not being maintained but the car produced no dashboard warnings. Replacement part 36400-1XAA0, warranty repair. Thanks to Joey R. for the detailed report and redacted repair order.
Added fourth column to the Section 2 failure mode comparison table: “OBC + Silent LDC Failure” — documents the pattern where both OBC and LDC functions are affected but no dashboard warnings are produced.
Added “Dashboard warnings” row to the comparison table across all four failure modes.
Added known ICCU diagnostic trouble codes table to Section 4 with five DTCs: P1A9096 (LDC, previously documented) and four OBC-side codes — P1E011C, P1E0211, P1E1300, P1E0C73 — sourced from Kia TSB SC302 and Hyundai Recall 257. Includes explanation of PFC (Power Factor Correction) and how the OBC-side codes relate to the charger’s front-end conversion stage.
Added warning callout to Section 4 noting that not all failures produce the expected warning cascade. References the Joey R. case where the 12V drain was only discovered through independent checking. Advises owners to check 12V independently if AC charging has failed, regardless of dashboard status.

March 3, 2026

Added 36401-1XFB0 to the known ICCU part numbers table — UK warranty replacement, EV6 (Aug 2025 build). OBC failure with LDC also degraded. First UK-market data point. Updated count from twelve to thirteen known part numbers. Thanks to Sasha for the OBD data and report.
Added 36401-1XAD6 to the known ICCU part numbers table — 2026 Ioniq 5 SEL (NACS-equipped, Oct 2025 build). Updated count from thirteen to fourteen known part numbers. Thanks to Chris for the OBD data.
Updated “emerging data” date stamp from mid-February to early March 2026.

February 25, 2026

Added source attribution to ECO mode 12V charging reference. Previously described as “owner monitoring data” with an “Owner-verified via OBD” badge; now links to the original KiaEVForums thread and badge updated to “Community-verified via OBD.” Softened claim language from definitive to observational.
Updated 36400-1XAD6 in the part number table: previously documented only as factory-installed in a 2026 Ioniq 5 Limited. A dealer repair order confirms the same part number is also being used as a warranty replacement on a 2025 Ioniq 5 (Jan 2025 build).

February 24, 2026

Corrected ICCU architecture diagram: V2L power conversion was shown under “Related modules” outside the ICCU boundary. The DC-to-AC conversion for V2L is actually performed by the OBC running in reverse — inside the ICCU. Only the passive outlet adapter and relay hardware are external. Confirmed via Alex Whittemore’s physical teardown of the V2L connector, which found the adapter contains only a switch, resistor networks, and a thermal fuse — no power conversion. Thanks to a reader for flagging the discrepancy.
Added community survey data modal to 12V battery recommendation section: 148-response informal questionnaire from a Facebook group showing ICCU failure rates by battery type (OEM lead-acid 13.5%, AGM 0%, replacement lead-acid 17.6%). Includes caveats about non-scientific methodology. Thanks to Paul K. for sending this in.

February 23, 2026

Added 36400-1XAD6 to the known ICCU part numbers table — 2026 Hyundai Ioniq 5 Limited (NACS-equipped, Sep 2025 build), reported via OBD scan on KiaEVForums.
Added 36400-1XFB0 — non-US CCS variant (2022–2024 MY), from recall notice and OEM parts sites.
Added 36401-1XFD5 — 2025 Kia EV6 GT-Line (NACS, May 2025 build), owner-reported OBD data on KiaEVForums.
Updated count from nine to twelve known part numbers.

February 22, 2026

Fixed part number typo in the Roscoe case study: 36480-1XAA0-A → 36400-1XAA0-A (confirmed from original repair order image).
Added 36400-1XAA0-A to the known ICCU part numbers table as a Hyundai Ioniq 5/6 replacement (CCS, 2022–2024 MY). Updated count from eight to nine known part numbers.
Added Hyundai TSB 24-EV-004H (July 2024) reference — covers ICCU replacement procedures for Ioniq 5/6 when DTC P1A9096 is present or AC charging is inoperative.
Corrected the dropped-nut service note: previously stated a dropped fuse nut “requires dropping and disassembling the entire HV battery pack.” The TSB actually provides a panel-removal recovery procedure; Techline escalation is only a fallback if that fails.
Updated the lithium 12V battery note in Section 9: added a link to an EE's detailed analysis of observed LDC behavior differences with a lithium unit, with a note that EV-specific lithium batteries (Ohmmu, etc.) include a BMS meant to handle the chemistry difference.
Added inline LDC/OBC subsystem tags to all 10 mitigation recommendations in Section 9, so readers can see at a glance which strategies primarily help the LDC (12V converter), the OBC (charger), or both.
Moved “Don't charge immediately after hard driving in extreme heat” from #9 to #5 based on multiple owner reports of failures after plugging in right after a long drive.
Tightened the surge protector recommendation (#8): removed redundant NEC adoption detail, integrated the separate OBC failure callout into the main text, and cut overlap with the dedicated circuit recommendation.
Clarified recommendation #5 and the thermal soak contributing factor to specify AC charging — DC fast charging bypasses the ICCU entirely, so the cooldown advice applies to Level 1 and Level 2 only. Thanks to a reader for pointing out this needed clarification.
Changed all mentions of “revised hardware” to “revised part numbers” throughout the report. No teardowns of revised units have been published and Hyundai Motor Group has made no public statements about what, if anything, changed internally. Claiming hardware was revised goes beyond what the evidence supports.

February 21, 2026

Changed "the EV6 has an Intelligent Battery Sensor (IBS)" to "E-GMP models have an Intelligent Battery Sensor (IBS)" in the BM2 installation note — the IBS isn't EV6-specific, it's present across the E-GMP platform.

February 20, 2026

Replaced BM2 installation video link with written installation guidance. The previously linked video showed the BM2 negative lead connected directly to the battery's negative post, which bypasses the Intelligent Battery Sensor (IBS) on IBS-equipped vehicles. Updated text explains that the negative lead should connect to a chassis ground point instead. Thanks to a reader for flagging this.
Added clickable 12V battery replacement procedure popup to mitigation table (items 3 and 4). Covers pre-installation best practices and IBS calibration steps, citing both the Kia and Hyundai owner's manual procedures as well as the E-GMP community-consensus procedure from service manual references. Notes the sequencing discrepancy between manuals and recommends owners consult their own model/year manual or dealer. Thanks to a reader for pointing out that there's more to a battery swap than just swapping the battery.

February 19, 2026

Added SC271 (July 2023) to Section 7 recall timeline — the first ICCU-related voluntary service campaign, covering 2022–2023 MY EV6. Previously missing from the table. Thanks to Dan S.
Corrected part number table in Section 8: 36400-1XFA0 is the original factory-installed ICCU. 36400-1XFA0QQK is the same hardware with a QQK suffix indicating a warranty/recall replacement part — it was previously mislabeled as the original. Split into two rows for clarity. Thanks to Dan S.
Removed speculative capacitor stress subsection from Section 2 ("The bigger picture: SiC switching and capacitor stress"). No teardown has confirmed capacitor failure as a cause. The independently verifiable electrical engineering was already covered in the converter design subsection.
Added context to Section 2: MOSFETs are ubiquitous in power electronics and MOSFET degradation under switching stress is a well-understood industry failure mode. The E-GMP ICCU's specific combination of 800V voltage, SiC switching, and ~300 kHz frequency creates significant stress on internal components.
Renamed "Remote climate pre-conditioning" to "Remote climate start" in Section 6 community theories table to avoid confusion with battery pre-conditioning for DCFC.
Corrected low coolant level entry in Section 6: clarified that the coolant reservoir is an expansion tank — slightly below MIN isn't a cooling emergency. The real risk is air in the system from running dry or improper bleeding after service. Updated mitigation section (item 2) for consistency. Thanks to Dan S.
Removed Torque News / Hyundai case manager quote from corporate acknowledgment section. The original source was a Facebook post (IonicGuy page) attributed to a Hyundai customer support representative — third-hand attribution that weakened the article. The on-record Kia spokesperson quote to Consumer Reports covers the same ground with stronger sourcing. Thanks to Dan S.
Section 9: Removed speculative claim that 12V battery symptoms "accelerate ICCU degradation" — replaced with straightforward "signs your 12V battery needs attention." Thanks to Dan S.
Section 9: "Avoids voltage fluctuations" changed to "Helps minimize voltage fluctuations" for dedicated circuit recommendation. Thanks to Dan S.
Section 9: Added note that ICCU failures aren't exclusive to 800V E-GMP vehicles — the 2023 Kia Niro EV (400V platform) has a documented NHTSA TSB (MC-10242579-0001) for the same failure pattern. The underlying design vulnerability may be broader than voltage class alone. Thanks to Dan S.
Corrected Ioniq 5 part number prefix from 36400 to 36401 — original entry used incorrect prefix. The OBD data clearly shows 36401-1XAA6. This is the first 36401-prefix part in the table; all other entries use 36400. Thanks to Jeff for the catch.
Removed unsupported predictive claim from mitigation table item “Monitor LDC output via OBD tool.” Previously stated “Consistently low readings may indicate degradation before a full failure” — most ICCU failure reports describe sudden failure, not gradual voltage decline. The healthy voltage ranges remain as a baseline reference. Moved this item from #6 to #10 — it requires extra hardware and knowledge, and the other mitigations are more directly actionable.

February 18, 2026

Added dealer diagnostic data from an Ioniq 5 OBC failure repair order: capacitance measurements at L&N (152.6 nF vs 23 nF spec), resistance reading, and part numbers. First quantitative diagnostic data for a confirmed OBC failure. Credit: Roscoe P. Coltraine (Facebook).
Added editorial note on 800V architecture and single-source component shortcomings (Section 9, editor's note)
Major correction to Section 1: The ICCU contains two subsystems (OBC + LDC), not three or four as previously stated. V2L is a separate physical unit that receives power from the ICCU. Charging communication is handled by the VCMS (Vehicle Charging Management System), a separate control module — not by anything inside the ICCU. Updated diagram to reflect this architecture with a clear separation between the ICCU and related modules. Removed "VCCU" acronym throughout — VCCU (Vehicle Charge Control Unit) is a standalone product made by ASELSAN, not an E-GMP component. Thanks to Tyler on the Ioniq Forum for the correction and the Kia wiring schematic (SD373-1) that verified the architecture.
Added terminology note clarifying that "OBC" on this page always refers to the AC-DC rectifier circuit inside the ICCU, not the entire ICCU assembly. Hyundai/Kia documentation uses "OBC" inconsistently.
Corrected MOSFET switching frequency in Section 2: previously stated "thousands of times per day" — actual switching frequency is ~300 kHz per goingelectric.de teardown (hundreds of thousands per second, hundreds of millions per day). Thanks to 79Bry on Ioniq Forum.
Accuracy pass across entire article: fixed internal inconsistency between main text and source attribution on switching frequency; corrected heated seat wattage figures in Section 5 (70W per seat, not 70W for both; steering wheel ~70W, not 120W; confirmed 12V via fuse box diagrams); softened "the fuse blowing" to "likely the fuse blowing" in Section 4; removed unsupported "hundreds of times per day" for bond wire thermal cycling in Section 3; updated structured data dateModified.
Removed Yahoo Finance / Oilprice.com article as a source. Earlier versions of this page relied on a Yahoo Finance article about EV capacitor risk for several claims in Sections 2 and 9, including direct quotes presented as "industry reporting." On closer review, the article was written for Oilprice.com (an oil industry publication) and syndicated to Yahoo Finance. The quotes were the author's own editorial framing, not attributed to any engineer or analyst, and several specific claims (BOPP film single-sourcing, 20–30% larger capacitors for 800V) were stated without sources. The independently verifiable electrical engineering (SiC dV/dt stress, ESR heating, polypropylene degradation) has been retained with proper sourcing. The capacitor-as-secondary-failure-pathway thesis is now sourced solely to an independent Reddit analysis by an EV6 owner with a power electronics engineering background.
Corrected "potted in resin" description of the ICCU to "sealed, liquid-cooled aluminum assembly." Teardown evidence (goingelectric.de, Circuit Board Medics repair service) indicates the internal PCBs are not encapsulated in potting compound.
Added Ohio State SiC Reliability Lab as source for the 100× interface defect density claim. The previously cited PMC paper (PMC11051854) covers threshold voltage instability, not defect density comparison — corrected the Sources section description accordingly.
Added EV9 ICCU part numbers to Section 6: original 36400-1XHA0 (from Kia OEM parts catalog) and revised 36400-1XHA1 (catalog confirms it replaces 1XHA0), plus corresponding HV fuse 375F2-D0040. Five ICCU part numbers now documented across E-GMP lineup. Thanks to Mike for submitting the dealer work order.
Removed "What the part numbers tell us" subsection from Section 6. It contained speculative interpretations (CCS/NACS explanation, claims about form factor and internals) that weren't backed by official documentation. The part number table now stands on its own.
Trimmed lithium 12V battery note in Section 5 mitigation table. Removed speculative detail about LDC charging profiles and OHMMU BMS edge cases. Replaced with concise recommendation: lead-acid is the designed chemistry, AGM is the community-recommended upgrade over the original flooded batteries, and Kia switched to factory AGM around February 2024.
Corrected failure mode comparison chart: LDC failure + AC charging previously said "May still work initially" — incorrect. When the LDC MOSFET fails and blows the ICCU fuse, it disconnects the entire ICCU (both LDC and OBC) from the HV battery. AC charging is not possible in any ICCU failure mode. Thanks to Kevin W.
Added safety warning to OBC failure section: do not continue attempting to AC charge after a suspected OBC failure, as each attempt risks further damage to the EVSE and electrical panel. Thanks to Kevin W.
Added service note about ICCU fuse location on HV battery pack frame and risk of rear nut falling into the battery during replacement. Corroborated by NHTSA TSB MC-11006095-0001 (ICCU Special Service Instructions). Reader Kevin W. flagged that early-build EV6 vehicles (on or before Feb 2022) are particularly susceptible due to unsecured fuse attachment nuts.
Added sixth ICCU part number: 36401-1XAA6 (2026 Hyundai Ioniq 5 Ultimate, NACS-equipped, Canada spec, manufactured Oct 2025). New base part number family (1XAA). Thanks to Jeff for submitting OBD data.
Added seventh ICCU part number: 36400-1XAD5 (2025 Hyundai Ioniq 5 XRT, failed at ~9,300 mi). Thanks to Randy M. for submitting the failure report.

February 17, 2026

Confirmed ICCU (as OBC) is covered under 10-year/100,000-mile EV System Warranty per Kia Connect warranty documentation; updated repair cost section from speculation to verified fact
Added forum report of ICCU replacement under recall at 108,000 miles, with context on federal recall obligations and mileage caps

February 16, 2026

Changelog created
Added News page to the site