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Left it out of garage. -13 when started and driven after a 2 minute "warm-up". First few stops the ISG did not activate. After another mile or two the ISG did activate, so presumably the coolant temp had become high enough at that point to meet Hyundai's ISG parameters. Drove for a total of 30 minutes and in some instances, the ISG did not activate. We're talking about a route spanning 10 residential blocks where I kept repeating streets and stops, using the same braking force and coming to a complete stop with firm pedal pressure. At one intersection ISG activated, then the next time after a lap, it did not. No settings changed in the car during this test. Hmmm...
 

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There are many parameters which must be met for ISG (Idle Stop and Go, or also known as Auto Stop/Start). I was able to access the Repair Manual and the Owner Manual electronically. Seems they have a bit different information in each one, so I've tried to net it down based on reviewing both of these documents. The purpose is to help people understand why the ISG may or may not activate in certain situations. There are some criteria that is not well defined (such as EMS State) so this is my interpretation of the requirements from both documents. I'll attach the information from the 2 sources as well.

If ALL the conditions are met ISG will activate:
- ISG Switch is OFF
- Engine Coolant Temperature is over 30?C (86?F)
- Brake Vacuum below -35 kPa
- Driver Door closed
- Driver Seat Belt latched
- Hood closed
- EMS State satisfied (TPS/CKP/CMP/WTS/Vehicle speed signal) - not sure I understand what all these mean or how they are satisfied.... I think they all indicate the vehicle is not moving and the throttle is not being pressed.....
- A/C System is satisfied (cannot find description of what it means to be satisfied)
- Battery State of Charge is over 68%
- Battery Temperature is between 2 - 55C (35.6 - 131F)
- ISG related parts have no errors
- Vehicle speed has reached greater than 8 mpg then decreased to 0 mpg
- Accelerator pedal is off
- Brake switch on or off (can be off if using auto hold)
- Gear state of N, D, R, 1, 2
- The vehicle is not in diagnostic mode
- The outside temperature is between 14 ?F and 95 ?F (-10 ?C and 35 ?C).
Note: In congested areas, if the driver wishes to stop the vehicle and change lever from D ==> N, the ignition will turn OFF
Note 2: 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.

If one of the following conditions is NOT met, ISG will not engage:
- ISG switch is pressed (off)
- EMS State not satisfied
- Driver's door open
- Hood open
- Driver's seat belt not latched
- Brake vacuum over -35 kPa
- A/C state not satisfied
- Battery State of Charge (SOC) less then 68%
- Battery Temperature above or below the range of 2 - 60C (35.6 - 140F) (NOTE: Information from the Repair Manual - not sure why this is 60C as the requirement for engagement as listed above is only 55C)
- ISG system component is in error
- Steering Wheel angle (cannot find any documentation on what that angle is)
- A/C System switch on, fan speed greater than 6th mark
- Defroster On
- Downhill or steep uphill (cannot find any documentation on what that angle is)
NOTE: When 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 which will force the restart of the engine during Auto Stop/Start
- Brake vacuum over -35 kPa
- Low Battery Voltage - Maintain excessive electrical load for 3 minutes
- Defroster turned on
- Open driver's door
- Unlatch driver's seat belt
- Open hood
- Engine has been off (auto stop) for 300 seconds (5 minutes)
- Sitting on a steep slope (don't know what the angle is for this to engage)
- ISG button pressed off
- A/C performance - A certain period of time has elapsed with the air condition ON. (cannot find specifics on duration or conditions regarding this requirement)
- A/C fan speed over 6th speed
- 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: In case of error during idle stop, the engine can only be started by using the key.


ISG system deactivation by fault.
- 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
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.
 

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I’m thinking it’s the battery charge level. Mine varies in the 70% vicinity. When it dips below 68% the ISG doesn’t activate. Here’s the question. We all have relatively new vehicles with new batteries. Why are these batteries not charging to well above the 68-72% level?!
 

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Is there a link that can be shared for the entire Repair Manual?

Cheers
I purchased mine from https://www.factory-manuals.com/hyundai-35 and they are based on your VIN. It is sold for $79.99. Comes to you in PDF format and is supposed to be "keyed" to your VIN/ID. So, I won't post publicly, but if you need a page or two, send me a private message and I'll try to help you out. Attached a screenshot of the 1st page and index. I have found a couple of inconsistencies but overall gets me to what I need. Sure beats paying the dealership for information.

From what I understand, this company creates a user ID specific to you on the Hyundai Support site and prints everything to PDF for your vehicle. Since access is for a short time, they must have a script or program that does this for you. Takes a couple of days to get the manual but I've purchased one for my Santa Fe and one for my F150. They have saved me a lot of headache and frustration when needed. While I hate to spend the money, it isn't overly expensive and does have a lot of information. I wish there was a place online that was free and had all this information.
 

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I also had issues with the ISG. It got to where it would never come on. Had it back to the dealer several times and although they could get it to work for a day or so, it would always seem to stop working again. Finally they tracked it down to the battery which they said had a dead cell. Once the bad battery was replaced, the system has worked well (fingers crossed) for the last several weeks. It does take a few miles for the car to warm before the ISG will function and when running the air conditioner/heater the ISG may not function if the interior temp is not at its setpoint. Other than that, it does appear to be working.
 

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I have times when the ISG works fine. at stopped lights, car engine will shut down and ISG Symbol will light up green. Most times however, The symbol will light up orange, and will not activate during a long stop. Why is this? the owner manual states that the prerequisites for ISG must be met. I cant seem to figure out why it wouldnt be running on my vehicle. Anyone else having this issue, or know why this is?
Yup, Owned mine for 4 months. The dealer tells me there is nothing wrong. I have seen it shut off a total of 20 times in 4 months. Three weeks with it not shutting off once. One trip, about 40 red lights, and it shut off once and not the other 39 times. The dealer doesn't believe me. ALL the conditions are met, (that I can do anything about). I have no control over vaccum pressure or battery voltage.
 

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Same thing happens to me, there are times where the orange light comes on. I thought I haven't "met" all the conditions for it, but have been trying to figure out what the exact prerequisites are.

From my personally experience, when I give a firm press on the brake as I stop (not sudden stop but stopping, then firm press?) it seems to activate ISG more often.

I'd love to know any input on this as well.
Yup, Owned mine for 4 months. The dealer tells me there is nothing wrong. I have seen it shut off a total of 20 times in 4 months. Three weeks with it not shutting off once. One trip, about 40 red lights, and it shut off once and not the other 39 times. The dealer doesn't believe me. ALL the conditions are met, (that I can do anything about). I have no control over vaccum pressure or battery voltage.
 

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I’m a big fan of the way the ISG works on our vehicles...when it works. Mine stopped working 4 days ago and nothing “under my control” can make it work. I already see a local mpg decrease of at least 1.5 mpg.

When it works, the ISG is smooth AND it does save gas. My ISG has actually gotten even smoother in operation over my 3.5 months of ownership.

Some folks would be thrilled to have it permanently disabled. I chose to get it serviced next week. It’s likely a faulty sensor.
Yup, Owned mine for 4 months. The dealer tells me there is nothing wrong. I have seen it shut off a total of 20 times in 4 months. Three weeks with it not shutting off once. One trip, about 40 red lights, and it shut off once and not the other 39 times. The dealer doesn't believe me. ALL the conditions are met, (that I can do anything about). I have no control over vaccum pressure or battery voltage.
 

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We've had our SF 2.0 AWD Ultimate for just about 6 weeks and put on over 2200 miles and the ISG function has never worked once, period! Always get the orange ISG light every time, can't figure it out. I did notice that the battery is at 66% today and yesterday it was at 64% if that matters greatly? BTW, we're in a cold climate so maybe that has something to do with it? :confused:
Yup, Owned mine for 4 months. The dealer tells me there is nothing wrong. I have seen it shut off a total of 20 times in 4 months. Three weeks with it not shutting off once. One trip, about 40 red lights, and it shut off once and not the other 39 times. The dealer doesn't believe me. ALL the conditions are met, (that I can do anything about). I have no control over vaccum pressure or battery voltage. BTW, it won't work with heating elements turned on (heated seats, steering wheel, rear window defroster), or the AC on full and the outside temp about 35 degrees C. That's what the manual says.
 

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The Hyundai ISG criteria is not well stated in the owner's manual, and I've not seen it posted elsewhere. However, I have a F150 with the Auto Start/Stop (same as ISG for Hyundai) and Ford does list some pretty specific criteria for the Auto Start/Stop to engage on the F150. While I know it may not be the same exact criteria, one can assume it is similar. So, just as a reference, I'll post the criteria for the Ford F150 in the attached PDF file. Hope it give you all an idea of the parameters necessary before the ISG engages.

Also, this seems to be a feature that people really like or dislike. I'm not here do discuss the merits or convince others of my opinion, I'm really dislike this feature and would like to disable it like has been done on my F150. If anyone knows how to do this (without really hacking the vehicle up), I'd sure like to know how it is disabled..... Please share if you know how to disable it or default it to be disengaged upon startup.
This is how I disabled mine- Pushed & "held" the button depressed to disable it and then inserted a tooth pick in the gap between the switch & console. I left the toothpick in for a few days to make sure there were no problems. I later replaced the toothpick with short piece of a Black nylon wire/zip tie. It has been that way for 3 months now. No problems at all for me.
 

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ISG worked 95% of the time in the manner I wanted/expected. The 5% is where I hated, prior to parking, forgot to apply light brake pressure in traffic and it stopped but I needed to go at the same time, ouch..
 

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Thanks to everyone who has contributed to this thread. It was informative.

In my case, I didn't even know my vehicle had this feature until I dug into the manual, after wondering what that button did on the console. As I live in Arizona, and it is currently summer, I don't expect to see this feature activate anytime soon (115 Fahrenheit yesterday).

I did find an article from 2012 that explains how Hyundai's ISG works, in plain language. It doesn't appear to have changed much since then. It's a good read:

I suspect this feature is more about getting bonus points for fuel efficiency from regulating agencies, than about a feature that is truly useful to owners. But, what do I know, I have never seen ISG in action.



Mike
 

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Thanks to everyone who has contributed to this thread. It was informative.

In my case, I didn't even know my vehicle had this feature until I dug into the manual, after wondering what that button did on the console. As I live in Arizona, and it is currently summer, I don't expect to see this feature activate anytime soon (115 Fahrenheit yesterday).

I did find an article from 2012 that explains how Hyundai's ISG works, in plain language. It doesn't appear to have changed much since then. It's a good read:

I suspect this feature is more about getting bonus points for fuel efficiency from regulating agencies, than about a feature that is truly useful to owners. But, what do I know, I have never seen ISG in action.



Mike
It certainly should work after dark when it cools down a bit in Arizona, etc. 95° is the cutoff.
 

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It certainly should work after dark when it cools down a bit in Arizona, etc. 95° is the cutoff.
Well, I suppose I could get up at midnight, when it finally gets below 95, but I doubt it. :)

BUT, I did try it today as I had to go out early, and it was, for here, a coolish morning (89F). After realizing I needed to more-firmly press on the brake pedal it worked like a charm. I was impressed how seamless it was, and more importantly, how fast it restarted when I lifted off the brake pedal. When I got to my destination I waited for a bit, with IFS engaged and engine turned off, and the A/C was still blowing cold (only waited about a minute).
 

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The Hyundai ISG criteria is not well stated in the owner's manual, and I've not seen it posted elsewhere. However, I have a F150 with the Auto Start/Stop (same as ISG for Hyundai) and Ford does list some pretty specific criteria for the Auto Start/Stop to engage on the F150. While I know it may not be the same exact criteria, one can assume it is similar. So, just as a reference, I'll post the criteria for the Ford F150 in the attached PDF file. Hope it give you all an idea of the parameters necessary before the ISG engages.

Also, this seems to be a feature that people really like or dislike. I'm not here do discuss the merits or convince others of my opinion, I'm really dislike this feature and would like to disable it like has been done on my F150. If anyone knows how to do this (without really hacking the vehicle up), I'd sure like to know how it is disabled..... Please share if you know how to disable it or default it to be disengaged upon startup.
This is how I disabled mine- Pushed & "HELD" the button depressed (to disable the ISG) and inserted a tooth pick in the gap between the switch & console. I left the toothpick in for a few days to make sure there were no problems. I later replaced the toothpick with a short piece of a Black nylon wire/zip tie. Leave enough sticking up so you can remove it etc. Mine has been disabled for 3 months now. No problems at all for me. Santa Fe SE
 

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The Hyundai ISG criteria is not well stated in the owner's manual, and I've not seen it posted elsewhere. However, I have a F150 with the Auto Start/Stop (same as ISG for Hyundai) and Ford does list some pretty specific criteria for the Auto Start/Stop to engage on the F150. While I know it may not be the same exact criteria, one can assume it is similar. So, just as a reference, I'll post the criteria for the Ford F150 in the attached PDF file. Hope it give you all an idea of the parameters necessary before the ISG engages.

Also, this seems to be a feature that people really like or dislike. I'm not here do discuss the merits or convince others of my opinion, I'm really dislike this feature and would like to disable it like has been done on my F150. If anyone knows how to do this (without really hacking the vehicle up), I'd sure like to know how it is disabled..... Please share if you know how to disable it or default it to be disengaged upon startup.
The Hyundai ISG criteria is not well stated in the owner's manual, and I've not seen it posted elsewhere. However, I have a F150 with the Auto Start/Stop (same as ISG for Hyundai) and Ford does list some pretty specific criteria for the Auto Start/Stop to engage on the F150. While I know it may not be the same exact criteria, one can assume it is similar. So, just as a reference, I'll post the criteria for the Ford F150 in the attached PDF file. Hope it give you all an idea of the parameters necessary before the ISG engages.

Also, this seems to be a feature that people really like or dislike. I'm not here do discuss the merits or convince others of my opinion, I'm really dislike this feature and would like to disable it like has been done on my F150. If anyone knows how to do this (without really hacking the vehicle up), I'd sure like to know how it is disabled..... Please share if you know how to disable it or default it to be disengaged upon startup.
This is how I disabled mine- Pushed & "HELD" the button depressed (to disable the ISG) and inserted a tooth pick in the gap between the switch & console. I left the toothpick in for a few days to make sure there were no problems. I later replaced the toothpick with a short piece of a Black nylon wire/zip tie. Leave enough sticking up so you can remove it etc. Mine has been disabled for 3 months now. No problems at all for me. Santa Fe SE
 

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Well, I suppose I could get up at midnight, when it finally gets below 95, but I doubt it. :)

BUT, I did try it today as I had to go out early, and it was, for here, a coolish morning (89F). After realizing I needed to more-firmly press on the brake pedal it worked like a charm. I was impressed how seamless it was, and more importantly, how fast it restarted when I lifted off the brake pedal. When I got to my destination I waited for a bit, with IFS engaged and engine turned off, and the A/C was still blowing cold (only waited about a minute).
Yes, the ISG is really very smooth and “seamless” is a good description.
 

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Hi everyone. I am new to this form and found it as I was trying to troubleshoot my system.
I noticed that my ISG doesn’t come on anymore unless I charge my battery over night, then it works for a few days and stops again.
I had my battery tested twice now, once at the dealer and it registered 73% SOC and had it done weeks later at autozone and it registered 76% SOC. Is that normal ?
if that battery hovers at that range all the time, then the ISG will rarely come on.
Dealer doesn’t really want to replace the battery because it’s “technically” testing GOOD.
Any thoughts?
 
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