Please delete this post. Sorry.

 

Edit: I should do a search and probably shouldn't have posted this. Sorry!

Will people now be jumping all over you for telling yourself that you should search here 1st, rather than provide helpful advice???? How mean you are to yourself! You should provide yourself with helpful advice, rather than snarky comments! You may have to exit this forum because of how mean you are to yourself....

 

Much of this has been discussed in other threads so a search would probably have revealed some insight. I will also add my best guess, which is battery State of Charge (SOC). Modern vehicles do not continuously charge the battery. Continuous charging requires more fuel - I know it is a very tiny amount of fuel but the vehicle will only charge enough to keep the vehicle able to start, but do not keep the battery fully charged (optimize fuel economy). My guess is that the battery seldom exceeds 80% SOC, and ISG quits engaging below 68% SOC. As the battery ages it won't recharge as well as when new. In addition, if you seldom drive, or take short trips, the battery will not get recharged and the SOC will slowly drop. I cannot prove this, it is my opinion based on multiple places of information. It is my best guess, and I'd bet if you put a charger on your battery and fully charged it over night, or put in a new battery, ISG would resume working (that is an easy way to prove me right or wrong). Since you asked about it on the forum, I'm just sharing my thoughts! I doubt a dealer will find an issue but that is always an option to take it in and have them check it out.

I've searched multiple locations to gather the list of criteria necessary for ISG to engage. This is what I've found.

If one of the following is NOT met, ISG will not engage:

• ISG switch is off (illuminated)
• Engine Coolant Temperature is greater 30°C (86°F)
• Brake Vacuum less than -35 kPa
• Driver Door closed
• Driver Seat Belt latched
• Hood closed
• EMS state (TPS/CKP/CMP/WTS/Vehicle speed signal) satisfied (DPF Regeneration prohibited) Not sure what all this means but it is a requirement…..
• A/C system satisfied = A/C switch ON, FATC over 6, MTC over 3 (The fan speed of the automatic climate control system is set above the 6th position, with the air condition ON)
• Battery State of Charge greater than 68%
• Battery temperature in this range: 2 - 55°C (35.6 - 131°F)
• No ISG related part errors
• Vehicle speed has reached greater than 8 MPH prior to vehicle speed reduced to 0 MPH
• Accelerator pedal not pressed (resting position)
• Gear state in R, N, D, 1 or 2
• Brake Switch activated (can be released if Auto Hold is active)
• Vehicle is NOT in diagnostic mode
• The outside temperature is between 14 °F and 95 °F (-10 °C and 35 °C)
• Battery Sensor deactivated (such as disconnected from negative pole for maintenance)
• Defrost switch ON
• On a downhill or steep uphill (I have not found the necessary angle documented)
• Steering Wheel angle (I have not found the necessary angle documented)

Note 1: When Auto Hold is activated, if you release the brake pedal, the engine will be in the auto stop state. However, if you depress the accelerator pedal, the engine will start again.

Note 2: In congested areas, if the driver wishes to stop the vehicle and change lever from D→N, the ignition will turn OFF. If the shift lever is shifted from N (Neutral) to R (Reverse), D (Drive) or Manual shift mode without the brake pedal depressed. A message "Press brake pedal for Auto Start" will appear on the LCD display. To activate auto start, depress the brake pedal.


Conditions for a FORCED restart:

• Brake Pressure Over -35 kpa
• Low battery voltage
• Maintain excessive electrical load for 3 minutes (I cannot find a documented definition of excessive load)
• Activate defroster
• The door is opened or seat belt is unfastened when the brake pedal is depressed or Auto Hold is activated
• Inertial speed over 1.5 km/h (on downhill)
• Ignition switched ON with hood open
• Engine stopped longer than 300 seconds (5 minutes)
• Vehicle parked on a steep slope (I cannot find a documented slope angle)
• ISG Off button pressed
• A/C ON, FATC over 6, MTC over 3 or HVAC performance dissatisfied (The fan speed of the automatic climate control system is set above the 6th position, with the air condition ON)
• A certain period of time has elapsed with the air condition ON. (I could not find a documented duration)
• The vehicle is shifted to P (Park) or R (Reverse) when the brake pedal is depressed or the Auto Hold is activated.
• The EPB is pressed when the Auto Hold is activated. (if equipped with EPB (Electronic Parking Brake))

NOTE: Notice: In case of error during idle stop, the engine can only be started by using the key.



The ISG system is deactivated by fault for the following reasons:

• Fault in communication line (LIN/CAN)
• Fault Electric oil pump
• Fault ESP System
• Fault Limp home mode
• Fault brake booster vacuum pressure sensor
• Fault Brake master cylinder pressure sensor
• Fault Brake pedal switch
• Fault Battery sensor

NOTE: When the ISG related sensors or system error occurs, the ISG OFF switch lights up. Especially when the battery sensor is replaced or reinstalled, the vehicle must be placed in the ignition switch OFF for about 4 hours for recalibration. The ISG function should operate properly in approximately 4 hours. However, for the first 25 times, the ISG function will operate regardless of recalibration.

 

Modern vehicles do not continuously charge the battery. Continuous charging requires more fuel - I know it is a very tiny amount of fuel but the vehicle will only charge enough to keep the vehicle able to start, but do not keep the battery fully charged (optimize fuel economy).

Is this documented anywhere for a 2020 Santa Fe 2.4? The Hyundai dealer doesn't admit to knowing anything about it.

I have a battery monitor and data logger software I use on my car. It records a reading every two minutes. When I leave on a 100-mile trip with a battery voltage above 12.6, the alternator will continuously charge the battery between 14.29 and 14.36 volts.

If my engine is running, my alternator is charging full speed ahead. Full time, every time. No exceptions.

 

Thanks for the detailed info. I do short trips around town, sometimes just once per day. Seems like it's the battery. But other than the ISG, there doesn't appear to be any issues with the battery, I'll ignore the "problem." Thanks.

 

IMO, it is an ill design. If it works in ur SF, great (it is undesirable in some situations 😂); otherwise MEH. Don't waste your time trying to get it fix. How to fix something that doesn't work consistently, like how do u know it is fixed? 😆

 

Ignore it?
Really?
If it is the battery it's a simple fix.
Your short trips may require a battery maintainer being used.

 

Don't dwell on the battery thing as reported by others. Battery defect is uncommon when near new. I believe there is a design issue, and Hyundai chooses not to spend the resource to fix it due to not a critical issue.

BTW, mine still work but only in periods, like works for a few weeks/months then not work for a.few weeks/months. It also worked in winter temperature too. Maybe too much frizzy logic in the algorithm 😆.

 

6-mo follow up. I started another thread about my Santa Fe breaking down and needing repair. Dealership said the throttle body was dirty (at 34k miles, no less.) Brought the vehicle home today and the ISG works again! go figure.

 

ISG didn't work for 1.5yrs now, don't really care.

 

I took mine to the dealer a month ago. They replaced a battery sensor, they said it was reading the wrong voltage. Still didn't fix it.

 

Guess what ....
After 1.5yrs in dormant, ISG worked yesterday and today, it worked well as expected; I didn't do anything.

 

Mine started working as well....but I have started going back into the office everyday for 2 weeks now. I attribute this to the battery getting adequate charge.

 

There are a bunch of other requirements, so you never know why it doesn't engage. It's a useless and gimmicky feature IMO, so I always turn it off. Besides, with 100F ambient temps for months, it only shuts off for a second, making it worse than not shutting off at all. And I always try to time red light or stops, so if I have to stop, it's only for a second or two tops, again, only making matters worse for me. Glad the 2023 G70 2.0T doesn't have that crap. Ha ha. But it's an old platform. All new ones are going to have it. At least the **** thing is still defeatable now; it might not be in the future.

 

This is so creepy. The ISG on my 2019 2.5l worked for the first time in at least a year this morning as well. And I had 3,000 mile road trip in there that would've given it plenty of time to get a good charge.

 

Interesting.

 

A little googling revealed that battery capacity increases at higher temperature, although it’s at the expense of battery life. At colder temperatures there’s less capacity but also less degradation to battery life. I wouldn’t be at all surprised if the hot temperatures are what caused mine to start working again.

 

i am aware that battery SOC is a permissive to ISG. But it was active 5 days per wk for the past 1.5yrs, and the past 3-4 wks were also hot. Therefore, I can't accept battery is culprit, not in my case.

BTW, still works, it worked so well that I had to disable it a few times to avoid short cycle lol

 

Here I was going to ask what did you all do to make it NOT work.
Hate the thing and always disable it every time I start the car.

 

Here I was going to ask what did you all do to make it NOT work.
Hate the thing and always disable it every time I start the car.

Here is the best $100 you'll spend..... Good company, and they have been selling auto stop eliminators for Ford, Chevy and GMC trucks for a long time. Glad they now have a solution for the Santa Fe. Simple to install, I did not read their instructions, but most likely installed in the console by the shifter. And I like that it is plug-n-play with no wire splicing.
Autostop Eliminator for 2019-2020 Hyundai Santa Fe

 

Perhaps it has been fixed for 2021+ SF?
It worked as expected when new, for ~1.5yrs. After that, it workded for a few days/weeks, then went to hibernation for a long time; the cycle repeats, unfortunately the off cycle was much longer that the on cycle. The times that it didn't work during the worked period, I understood why because the reasons were in the manual. But no clue what triggers the stop cycle and the start cycle lol. IMO, it is an ill design, inadequate test; the fix requires a software patch.

 

If the battery drops below a certain level, I've heard 80-90% but who really knows, then ISG is automatically disabled. You can see this if you live in a colder climate on the first start of the day. ISG just won't work for about 10-15 minutes until the alternator can charge up the battery. Then all of a sudden it will start to work.

If you don't have a newer battery, you might want to get it load tested. I do know that the threshold seems to be very high, so just a 10-15% ? drop will cause ISG to disable itself.

 

Good theory, but not the reason for those with ISG not working correctly.

 

It only shows for up to a '20. Will it work on a '21 and up?

 

I don't know. Probably best to ask the company. If that doesn't work, go to Shark Racing (sharkracing.com) and purchase their module. You will have to wire it in yourself, but it includes the option to default AutoHold to always on. In addition, they sell a module for the Heated/Cooled seats which remembers your last setting. And you have to wire it in as well. Options, just hope you can find one that works for your desire/needs. Good luck.

 

I purchased a CPO 2019 Santa Fe SE in Dec. 2020. I have already taken it in once in Jan. 2021 for the ISG not working. They had to open a ticket with corporate to figure it out and ended up replacing the battery. Viola, the problem was fixed. Fast forward to 1st quarter 2022 and it is working less and less. Then it stopped working entirely in June. I called the same dealership (mid-June) that fixed it the first time and set up an appointment (sadly, the soonest appointment they had "available" was 1.5 months later). Now, they dicking around saying it doesn't work 95% of the time anyways.

I have read the previous posts and understand the intricacies discussed. I don't care why it fails. I purchased a CPO vehicle for a reason. I expect every function to operate correctly and if it doesn't, I expect it to be repaired under the CPO warranty.

Why is it that consumers today accept products that do not operate as advertised? Hyundai needs to feel some financial pain to goad them into taking care of this problem once and for all. What might help is if everyone who had this problem took it back to the dealer and made them fix it every time it happened - then they might come up with a solution that would correct it long term. The other alternative that might help is if a class action lawsuit was filed on this issue..

If this were a safety feature, there would be a recall and you can be sure Hyundai would have taken care of it post haste.

Is everyone so jaded that when they buy something, they expect it not to work?

 

I (most??) found it useful only on long red nights (say longer than 90s). Anything shorter I rpefer it not working. Definitely disable if only stops for a few seconds and perform parking manuver. So I don't bother wastimg the effort since the dealer cannot fix a software issue. I do agree that if everyone brings their cars in for this issue might get Hyundai to release a software patch to fix it.

 

Many of us don't care one iota about that feature, and think it's just a gimmick, so only hurting the starter, battery, and the engine. But at least in my case, it'd also hurt more the environment and fuel economy as well, because I always time traffic lights and stop signs, meaning if I stop at all, it's only for a second or two, making matters worse. But even if I stop longer, the darn thing restarts the engine almost instantly throughout the summer anyway (due to A/C not cooling), since it's in the 100s for months. That's the only thing I'm glad about the new 2023 G70 not having the 2.5T engine (Iike the twin Stinger), since it doesn't have that crap. I always turn it off, and sport mode on, so not a big deal to me that it doesn't have memory anymore. Glad to still have the option to turn it off .

 

I never want mine to work, that's why I push the off button.