Kia,Hyundai,Genesis ICCU Failures,Causes,Theories ,Warning signs,Mitigations,need to knows

Hello and welcome to another episode. In

Sunday's Kier Electric News, which is February 22nd, 2026, I covered a big article on a website called EGMP files.com that covers the reasons for

ICCU failures in 800 volt EVs such as the EV6 and EV9, the Ioni 5, 6, and 9.

This was created using AI research tools and also factchecking and also had input from electrical engineers to verify the details.

ICCU stands for integrated charging control unit. It's a big very important

control unit. It's a big very important box of tricks that handles 12vt battery charging, AC charging, and vehicle to load in your car.

Since Kier Electric News gets an audience of between 3 to 4,000 views each week, I thought it was worthwhile putting out a standalone episode with the same summarized breakdown with some

updated information that has come to light since hopefully this information will reach more owners of these vehicles because I think it's important.

The situation with Hyundai Motor Group trying to fix the ICCU issues is ongoing with new ICCU part numbers appearing in replacement units almost every week. The

actual creator of the EGMP files website, Aaron from New York in the US, contacted me in the comments to thank me for doing the video and to also give credit to the many community contributors and electrical engineers

for helping to pull all the info together. Anyway, a few updates since

together. Anyway, a few updates since Sunday. Since I made the video, I've

Sunday. Since I made the video, I've also noticed that there are already four ICCU failures for the Ionic 9 in the States, which is Hyundai's most recent

EV, most recently in January. So, it

shows that the Ionic 9 still has the ICCU issues. Up until early February

ICCU issues. Up until early February 2026, 5,389 have been sold in the USA.

So, at the moment, this is a very small proportion of vehicles sold.

Also, some of the comments in the UK pointed out that their dealers have said that fitting an AGM 12vt battery could invalidate their warranty, and that's a very good point. So, also bear this in

mind when considering ICCU failure mitigation measures, which are in the video.

Also, in the comments, I was asked if the facelifted models behave in the same way when using eco mode and charging 12vt battery. Although the only posts I

12vt battery. Although the only posts I can find relating to eco mode 12vt charging behaving differently are the prefaceelifted version facelifted EV6

and IonX6 have improved power electric system. So until someone does some

system. So until someone does some testing with car scar and OBD adapter in eco mode I can't say if it does behave the same way or not. Would be good if

someone who's as the equipment can actually do this though.

I was also asked in the comments if I'd heard of the ICCU moisture brief theory being the cause of ICCU failures. Well,

yes, I have, but I've also seen it discounted by many and ruled out.

Firstly, both NHTSA and Hyundai have given us the reasons in their recall documents, and it's not condensation.

Also, ICCUs and inverters are normally coated with a moisture repellent coating.

Today, February the 25th, Ted Smith on Ionic Guide Facebook with his Ionic 5 in for replacement ICCU in the States also confirmed another new part code. This

matches the last updated code on EGMP files change log. The part code is 36400-1X6.

Once again, it's still not known if any of these new parts contain the magic bullet fix, and only time will tell.

Also on Facebook this week on the Ionic Guy Facebook group and elsewhere because it's been spread around quite a bit.

David Seawitz published his research into failure rates of ICCUs using NHTSA complaint data. It's a great piece of

complaint data. It's a great piece of work, but the one thing I can see wrong is he has no way of knowing when the ICCU software updates replied. The first

voluntary recall for ICCUs was way back in July 2023.

These updates help slow down the failure rates by changing cooling systems and changing 12volt charging behavior to prevent the voltage spikes that would blow in the MOSFET that would stop

12volt battery charging.

In some of the ICC updates, they also added improved fault detection probably by monitoring the low voltage DC output that charges the 12volt battery. It's

been known uh that the output starts to reduce before the failure. So, so that also may have increased failure rates.

This is also reported several times on KIA EV forums, EV6 group and other places. So, without having a point in

places. So, without having a point in time actual dates that ICCU software updates were applied for each of ICCU failure complaints, I can't see how ICCU

failure rates can be accurately calculated. David, I do appreciate the

calculated. David, I do appreciate the huge amount of work that you put into this, but I think you need more data.

Anyway, I now present my slightly updated ICCU video segment with the official courses modes of ICU failure community hive mind failure theories and also a list of mitigations.

Before we go to that video though, here's a quick disclaimer from EGMP files website. Community research, not

files website. Community research, not an official document. This is a community source compilation. I'm an EV6 owner, not an EV technician. I'm using

the tools I have to better understand this issue and sort what's real from what's not. You should view this with

what's not. You should view this with the same skepticism you'd apply to any forum, Reddit or Facebook post. The

information here is gathered from the NHTSA filings, tearown videos, forum threads, and community discussion, then verified where possible against service manual data, and professional analysis.

Any mitigation strategies discussed should be to consider speculative without further guidance from Hyundai Motor Group. Use your own judgment based

Motor Group. Use your own judgment based on the information provided. Claims are

labeled by confidence level throughout.

If you spot an error, let me know.

Corrections are tracked and published in the change log. If you prefer to read the full article, which is much more detailed, then click on the link above.

Links to various items covered in this video can be found in the video description.

This week I came across an excellent but very long and detailed article from a website called EGMP files.com which covers ICCU failures on Hyundai Motor

Group Ioni 5 and six and EV6 and 9 and the GB60. This article does not apply to

the GB60. This article does not apply to the key EV3 4 or 5 which are different models of ICCU and do not have the same issues. This is written by an EV6 owner

issues. This is written by an EV6 owner who has gathered together all of the data using AI tools and then double check the sources are correct.

There are quite a few things he's discovered during this process that I was not aware of. I can't comment on the electrical engineering finding as I'm not an electrical engineer, but they

seem plausible from what I do know. All

the other stuff in the article seems to be factually correct. There is a link to the full article in the description which also goes into much technical depth and detail which if you fancy it

is there to read. I've tried to condense and summarize the parts I found most interesting from that article. Firstly,

it states that the failure rate is much greater than 1%. I agree with this. In

last week's K Electric News, Consumer Reports article reported up to 10% failure rate. That's from actual

failure rate. That's from actual consumer data. There are two failure

consumer data. There are two failure modes which we know about. I agree with that. Two of the ICCU subsystems can

that. Two of the ICCU subsystems can fail independently, and you'll see these abbreviations throughout this page. LDC

or low voltage DCDC converter. This

steps the high voltage battery power down to 12 volts. The it's the alternator replacement in an electric vehicle. If it dies, the 12volt battery

vehicle. If it dies, the 12volt battery drains on the car stalls. OBC or onboard charger. This converts external AC power

charger. This converts external AC power to DC for charging. If it dies, the car drives fine but can't charge from level one or level two AC and it may damage

your EVSC or AC home charger or trip your house circuit breakers in the process.

Two stresses are officially identified.

Firstly, MOSFET failure. MOSFET stands

for metal oxide silicon field effect transistor. This MOSFET is the internal

transistor. This MOSFET is the internal ICCU component that fails that causes the 12volt battery to stop charging.

One over voltage spikes. The active

clamp MOSFET experiences a voltage transient on every switching cycle 300 kHz and additional stress each time the LDC ramps apart down in response to 12vt demand.

of hundreds of millions of cumulative cycles per day. These transients damage the MOSFET chip. Two, thermal cycling.

The ICCU heats up during charging and driving, then cools down. This repeated

heating and cooling degrades internal components over time.

The short version, a MOSFET, a type of power transistor inside the LDC, gradually degrades until it shortcircuits. MOSFETs are ubiquitous in

shortcircuits. MOSFETs are ubiquitous in power electronics. They're in everything

power electronics. They're in everything from foam charges to solar inverters and MOSFET degradation under sustained switching stress is a well understood failure mode in the industry.

The EGMP ICCU operates at the intersection of 800 volts class voltage.

SIC semiconductor switching and a 300 kHz operating frequency, a combination that creates significant stress on internal components. That short draws

internal components. That short draws massive current from the high voltage battery. So the 130 amp internal fuse

battery. So the 130 amp internal fuse blows to prevent further damage. With

the fuse blown, the entire ICCU loses it connection to the high voltage battery.

The LDC can't convert to the high voltage power to 12vt, and the onboard charger can't accept AC charging either.

The 12volt battery drains with no way to recharge. Here's why the MOSFET degrades

recharge. Here's why the MOSFET degrades in the first place. The MOSFET LDC failure described Burb is the most commonly reported and the more critical of the two since it eventually kills the

car's ability to drive. But the LDC and OBC are independent of each other and EVA can fail on its own. When the OBC fails, it produces a completely different set of symptoms. When the OBC

fails, level one and level two AC charging stops working entirely. The OBC

converts external AC power to DC. If

it's dead, no AC charging is possible.

But you can still DC fast charge.

A DC fast charge just supplies DC power directly to the high voltage battery bypassing the OBC completely. So it

doesn't care about the ICCU. The OBC is simply not in the DC power path. The car

drives normally. The LDC is still functioning. So the 12vt battery stays

functioning. So the 12vt battery stays charged and all vehicle systems operate as expected.

Sometimes the EVSC or AC charger may be damaged.

So why is this progressive degradation not sudden event?

This is a critical point that's often misunderstood.

The MOSFET doesn't go from healthy to dead in one bad spike. It degrades

gradually over months or years through well doumented failure modes specific to SIC power semiconductors. The day it finally dies is just the day the last

transient pushed an already failing component past its threshold.

The failure event, the pop, the dashboard warnings, the car going into limp mode is the end of the long decline, not a bolt from the blue. This

also explains two things. One, why the recall software fix helps even though the hardware is unchanged. It slows the degradation curve by reducing transient severity. And two, why replacement ICC

severity. And two, why replacement ICC used with the same hardware design eventually fail again. Community

monitoring data via OBD tools like car scanner reveals that the LDC doesn't always charge the 12volt battery.

gently.

When the 12volt battery SOC drops below a state of charge, approximately 90%, the LDC can dump over 40 amps into it to bring it back up. For context, a healthy

steadystate charging current is in the 6 to 12 amp range. These high current events mean the LDC is ramping hard and frequently, each ramp producing the overvoltage transient that damages the

clamp MOSFET.

Actually, I've personally noticed this whilst monitoring my own EV6 before the recall software updates became available. So, I think it's very true.

available. So, I think it's very true.

Anyway, on with this. Eco drive mode makes this things worse. Owner

monitoring data shows that in eco mode, the 12volt charging current goes negative during acceleration. 12vt

battery drains faster than the LDC supplies and then spikes positive during regen braking. This creates constant

regen braking. This creates constant voltage oscillations effectively maximizing the number of damaging transient events per drive. Four,

how to recognize an ICCU failure. When

the MOSFET fails and the internal fuse blows, the 12vt battery loses only charging source. Symptoms typically

charging source. Symptoms typically appear in this order. One, an audible pop or clunk from under the back seat or thereabouts. Two, check electric vehicle

thereabouts. Two, check electric vehicle system warning on the dashboard. Three,

stop vehicle and check power supply.

Four, power limited warning. The car

begins limiting performance. Five, over

the next 20 to 45 minutes, the 12vt systems progressively fail as the battery drains.

Six, eventually the car shuts down completely and cannot be restarted.

Other signs that may indicate ICCU degradation before a full failure, 12volt battery repeatedly dying or needing jump starts. Now I've seen

owners in the UK with this LDC output voltage dropping below 13.5 volts check with car scanner app or with similar OBD

tool or diagnostic trouble code P1A 9096 stored in the system which you can check with car scanner. There is also widespread misconception that an ICCU

failure means the car instantly dies with no warning. This is not what happens. When the internal fuse blows,

happens. When the internal fuse blows, the 12vt battery stops being charged, but it doesn't stop working. The

remaining charge and 12vt battery keeps all vehicle systems running while it drains. Every documented real world case

drains. Every documented real world case follows the same pattern. Audible pop

dashboard warnings, progressive power reduction, and then eventual shutdown in that order. How much time you have

that order. How much time you have depends on the state of the 12vt battery, ambient temperature, and how many accessories are drawing power. A

healthy 12volt battery in moderate conditions gives you 20 to 45 minutes.

Even in a worst case, weak battery freezing cold, heavy accessory load, you will still have a minimum a few minutes of warnings, dashboard alerts, and reduce power drive before the car stops.

That is enough time to signal slow down and get to the hard shoulder and put your hazard warning lights on. This is

fundamentally different from a catastrophic engine or electrical failure in a conventional vehicle where loss of power can mean immediate loss of power steering, power brakes, and all electrical systems simultaneously with

no buffer and no warning. The ICCU

failure mode is progressive, not instantaneous. The danger is not the

instantaneous. The danger is not the failure itself. It's ignoring the

failure itself. It's ignoring the warnings and continuing to drive until the 12vt battery is fully depleted, at which point you use lights, hazard flashes, and propulsion. So you could be

stuck in a carriageway, which is what has happened.

So do not attempt to make it home. Pull

over safely. Activate your hazard warning lights while you still work and call roadside assistance. The car will not be drivable once the 12vt battery is fully drained and cannot be restarted at the roadside.

A recurring pattern in community reports is ICSU failures happening in the morning within the first few miles from home, often while backing out of the driveway.

Typical scenario, the car charged overnight. The owner turns on heated

overnight. The owner turns on heated seats and heated steering wheel and also has the heating on, shifts into reverse, and hears a pop. This isn't a coincidence. This scenario stacks every

coincidence. This scenario stacks every electrical stressor simultaneously.

Um, personally, I've actually seen this in my video comments quite a few times.

It also explains why the failures happen more in winter cuz you've got all your heat stuff on. So, what do the ICCU software updates actually do? The recall

software update addresses the failure mechanism in three ways. One, it soft starts the LDC. When the LDC begins charging the 12vt battery, it now ramps voltage gradually instead of switching

unabbruptly. This reduces the over

unabbruptly. This reduces the over voltage transient at turn on the primary stressor that damages the MOSFET. Two,

improve thermal management. This changes

to cooling fan and water pump operation that keep the ICCU at lower temperatures during operation, reducing thermal cycling stress.

Three, optimize charging behavior.

Adjustments to how the system handles voltage ripple during AC charging.

What the fix does and doesn't do that.

The software update slows the degradation curve by reducing the severity of each voltage transient and thermal cycling. It does not fix the

thermal cycling. It does not fix the underlying hardware vulnerability. Think

of it as turning a steep decline into a gentler slope. The component still

gentler slope. The component still degrades just more slowly.

The problem through late 2025 onwards um replacement ICUs with the original design failed again. Multiple owners

reported second failures 7 to 18 months after recall replacement. The

replacement part was the same hardware design. Transport Canada open a formal

design. Transport Canada open a formal investigation after 11 plus complaints of post recall ICCU failures.

2025 facelift models uh also reported ICCU failures suggesting the fundamental design issue persisted in current production.

The software update mitigated but did not eliminate the root cause. As of

midFebruary 2026, there were at least eight known ICCU part numbers across community sources, OEM cataloges, and reader submissions. Some of these appear

reader submissions. Some of these appear to be revised units, notably 36400-1X FA0 AQQ,

which began shipping around January 1526.

This coincided with an updated NHTSA bulletin. It's still not known if these

bulletin. It's still not known if these revised models provide a magic bullet to fix the problem. So, what can owners do to mitigate the ICCU failure risk?

No mitigation is guaranteed to prevent failure, but these actions address the known stresses listed roughly in order of importance. Confirm recall software

of importance. Confirm recall software is installed. The soft start fix is the

is installed. The soft start fix is the single most impactful mitigation. Check

with your dealer by VIN. Even if the SC 302, which is the the American code for it, was done, SC327 may still need be needed. These recalls have different

needed. These recalls have different numbers in the rest of the world.

Also, make sure you've got the limp home mode update on your REV6.

Two, check coolant levels after ICCU service or replacement or just check your coolant levels anyway. Three,

install the battery monitor on the 12volt battery. A Bluetooth battery

12volt battery. A Bluetooth battery monitor like the battery monitor BM2 is what I used. Four, keep the 12volt battery healthy. A healthy 12volt

battery healthy. A healthy 12volt battery reduces how often and how hard the LDC has to cycle. Fewer onoff

transients means slower MOSFET degradation. When it's time for

degradation. When it's time for replacement, an AGM battery is recommended and it's what Kia and Hyundai fit these days. Five, use a quality EVSC or AC charger certified

hardwired.

It reduces AC power quality issues reaching the ICCU. A hardwired

installation eliminates the plug connection as a potential source of resistance and heat. So, try not to use granny chargers cuz they're what they're basically talking about. Six, dedicated

circuit for the AC charger. This helps

minimize voltage fluctuations from other household loads on the same circuit. In

the UK, it has to be that way. You've

got a separate circuit breaker. And

avoid charging during storms or brownouts. Grid instability creates

brownouts. Grid instability creates exactly the kind of voltage spikes that stress the ICCU. Don't charge

immediately after hard driving in extreme heat. Let thermal management

extreme heat. Let thermal management system cool the ICCU before adding the additional heat load of charging.

Monitor LDC output via the OBD tool. My

car scanner which can read the LDC output voltage. Healthy voltages whilst

output voltage. Healthy voltages whilst driving the car is 14 to 14.5 volts. At

rest it's 12.4 to 12.8 volt which is normal. Consistently low readings may

normal. Consistently low readings may indicate degradation before a full failure. I would also add to

failure. I would also add to mitigations. Number 11. Consider

mitigations. Number 11. Consider

reducing the charging current in the EV setting screen to reduce the thermal load on the ICCU an onboard charger. I

charged my EV6 when had it at 60% charging current for many years and never had the ICCU fail. Next owner

wasn't so fortunate though. Even

reducing charging current to 90% could have an impact. Thanks for the author of that because it's a great article as I keep on saying. Um what have I got to

say? Um, and what about the newer 400vt

say? Um, and what about the newer 400vt models like the EV3, 4, and 5, you may ask? Well, so far I've not seen any

ask? Well, so far I've not seen any evidence of the 12vt charging failure issue that we've seen in the EV6, ionic 5s, and any of the other 800vt models.

What I have seen though is a few AC charging failure issues, which have led to ICCUs being replaced in some EV3s and also some slow charging AC issues, which

have led to replacements. There have

also been a small number of flat 12volt batteries on EV3s, but this is not caused by the ICCU. It's more likely a parasitic drain on the 12vt battery and we constantly get overtheair updates for

the drivetrain which fix some of these.

As for the Kia EV5, some may think it's a new car. It's only new to Europe. It

launched in China in 2023 and in Australia in 2024, so it's quite mature technology. And so far, I've not come

technology. And so far, I've not come across any issues until someone tells me different. Anyway, I hope you found this

different. Anyway, I hope you found this useful. Thanks for watching.

useful. Thanks for watching.