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Greetings all fellow Volt drivers and experts. I have a bit of information to share after having installed joesonvolt's ERDTT bypass temperature sensor I bought on eBay.

I have a 2018 Volt Premier, the Cajun Red (or is it Crystal Red?) paint color, that I bought and began driving at the end of January 2018. Soon after purchase, I made two significant modifications: #1: I brought it to a local shop and had a color-change vinyl wrap placed, making it "Gloss Plum Explosion" purple. #2: I purchased the 2018 ERDTT bypass temperature sensor on eBay, installed it according to the directions, and happily drove for the next year only using gas when I drove past the electric range.

I live in Minnesota, so this past January, about 1 year after buying the car, the check engine light came on, which I thought was funny, because the engine hadn't run for quite awhile. But then the remote start would not work (which I found out was directly related to the check engine light being on - they make it so that remote start will not work if the check engine light is on). So, that being annoying, I pulled out some Engine Control Module fuses, let it sit for like 15 minutes, put them back in, and turned on the vehicle. Sure enough, the check engine light was off, and the remote start was working again, yea!

A week or 2 later, the check engine light came on again, but this time the remote start did still work (?), however like the next day, I got an OnStar email that said "A problem has been detected with the Li-ion battery. Please bring your vehicle in for service within 7 days." Well that got my attention. Not knowing what exactly was wrong, I made the service appointment, and then remembered to remove the ERDTT bypass sensor using the same steps as installation, and brought it in.

About a day later, the dealership called me and said that it had been determined that section 3 of the Li-ion battery had some kind of fault, and needed to be replaced. They obviously did not have an extra section 3 lying around, so it needed to be shipped in, and it took several days (maybe a week?) to get fixed, which was all covered under warranty.

The whole event worried me a bit, wondering if the ERDTT bypass sensor could have contributed to the failure in that section of the battery? I decided after getting the car back to NOT reinstall the bypass sensor right away, so I went the rest of the winter without the bypass sensor.

So that is my question for the fellow Volt owners and experts: What do you think about that? I did a lot of reading before buying the ERDTT bypass sensor. It is supposed to not affect the thermal maintenance of the battery. But keep in mind that I live in MN, and I'm pretty sure that around the time that it started acting up in January 2019, we were getting some -20°F overnight lows, and some below 0°F daytime high temps. The car was unfortunately not parked in my heated garage much this winter, because I had been using the garage space to cut wood, etc. for house remodeling. But I did ALWAYS remote start the vehicle before driving (who wouldn't with those temps!), often beyond the 1st 10 minute cycle, I would begin a 2nd 10 minute remote start cycle.

On one hand, I can believe that it shouldn't have affected the thermal management of the battery, because its cousin, the Chevy Bolt has no ICE, and must do all of its battery thermal management using the battery itself. Could it be my driving habits? I don't consider myself as too much of a heavy accelerator, but I do kind-of hypermile a bit (putting into neutral while coasting, I use Drive to brake/regen slightly if I need to, Low gear for a bit more brake/regen, and the paddle for the heaviest brake/regen).

After receiving the OnStar email, I changed the driver display to show me the engine coolant temperature, and it was cold. At most, maybe a couple of degrees warmer than outside temperature. I didn't know if that display was the coolant that was cycling through the battery with its own electric heater module, but I think that is not the case - I think it's only the separate coolant loop of engine/cabin coolant, so I really have no way of knowing how the battery thermal management system was working at the time.

Anyways, enough rambling from me, I appreciate any responses from anyone with any insight as to this issue.
Thanks again,
SteveMoz
 

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I believe your battery pack issue was unrelated to you installing the modified OAT sensor. The air temperature sensor is not used to monitor or maintain the battery temperature. The battery temperature management system relies on multiple temperature sensors within the battery pack.

The ICE will run every 6 weeks due to Engine Management Mode activating regardless of the air temperature.

In addition to a check engine condition, the remote start/preconditioning function will not operate if the Volt senses that the hood is not fully closed; also if there is less than ~1.0 to 1.5 gal of fuel in the fuel tank.

Some Volt owners believe that Engine Assist Heat (sometimes conflated with Engine Running Due to Temperature (this is the message that briefly displays on the Volt's Driver Information Console) will warm the Volt's battery in addition to generating heat for the cabin. This is not the case; the Volt relies on a 2kW electric battery heating unit that is in-line with the battery coolant loop. The battery coolant loop is separate and disconnected from the engine coolant loop.
 

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I think @jcanoe is right about his analysis, although I know a fraction of what he does about the Volt.

The ERDTT kit still allows the ICE to run at some temperature threshold, doesn't it? I would think it should at least run at or below the defer setting on the 2019, which IIRC is -13F. Of course, one could just put it in Hold when it's that cold if concerned, or in need of more cabin heat, but the ERDTT would heat it up faster.

I live in St. Paul, MN and have considered this kit for our 2018, but my wife wants me to hold off until the basic warranty period is over.

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jcanoe is right, your issue with the battery wasn't related to the modded sensor this is just random badluck.

I had a Gen1 and now a gen2 volt for years and didn't have a problem with the modded sensor EXCEPT with the Gen 2, as soon the temps are below freezing temps, the check engine light will appear (Code P059F - active grille shutters not performing as expected) because the active front shutters will be stuck in ice and since and cannot open/close. The BCM receives a false temperature, it wants to operate the shutters thinking the temperature is OK to do so, but in fact, it's not. The BCM will not activate the shutters when it knows the temperature are at the freezing level thus preventing the CEL. This is the only problem I experienced with modded sensor.
We have to choose between getting the CEL and thus loosing the remote start function (at the moment we need it the most) or accept burning some fuel on very cold days. I know this is frustrating.

GM corrected this in the MY 2019 volt the ERDTT will operate only on very very cold days (-25 degrees Celcius is I recall correctly)
But I guess GM is unable to reprogram our "old" Volts to this value, which is something Telsa does with their products...

I live in Canada, so I feel your pain.
 

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The whole event worried me a bit, wondering if the ERDTT bypass sensor could have contributed to the failure in that section of the battery?
Yes, if your problem is related to the battery getting cold.

Chapter 9 of the Volt Factory Service Manual states that the same engine control module that triggers ERDTT also triggers the heating functions for the battery when the car is on and when the car is charging. If it is fooled regarding the ambient temperature, the manual reads like the battery heating could be delayed.


I did a lot of reading before buying the ERDTT bypass sensor. It is supposed to not affect the thermal maintenance of the battery.
I'm not sure how anyone would truly know unless they are a GM engineer and have access to the car's programming. The Service Manual implies that bypassing the sensor would definitely trip up battery heating in some situations.


On one hand, I can believe that it shouldn't have affected the thermal management of the battery, because its cousin, the Chevy Bolt has no ICE, and must do all of its battery thermal management using the battery itself.
The Volt's battery heater is also an electric one (presumably like the Bolt), but if the car/module is fooled to think it's warmer outside than it really is, the battery heater may not come on at the proper time. It sounds like the Volt will delay that battery heating (in some circumstances) just like it would delay the engine coming on for cabin heat when the ERDTT bypass is installed.
 

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Why would the Volt's battery TMS rely on the OAT sensor and waste energy heating or cooling the battery when there are battery temperature sensors? Especially while the Volt is parked the battery temperature will change much slower than changes in the air temperature.
 

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I'm not sure how anyone would truly know unless they are a GM engineer and have access to the car's programming. The Service Manual implies that bypassing the sensor would definitely trip up battery heating in some situations.

Does Frank Weber, Volt chief engineer count?

The location of the air temperature sensor that controls ERDTT, how it operates and the theory that adding a 1/8W 39K Ohm resistor could cause the car to see a higher temperature was originally posted on GM-Volt by our own WOT (with GM at the time) and Tboult. Subsequently others, including Frank Weber (Volt chief engineer, now BMW i3), used this information to create a mod that prevented ERDTT.

https://gm-volt.com/forum/showthread.php?127761-ERDTT-Modification-Options&p=1758281#post1758281

Regardless, I (and others) have been running this mod for years without issue. Chicago get plenty cold in the winter.
 

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Does Frank Weber, Volt chief engineer count?

The location of the air temperature sensor that controls ERDTT, how it operates and the theory that adding a 1/8W 39K Ohm resistor could cause the car to see a higher temperature was originally posted on GM-Volt by our own WOT (with GM at the time) and Tboult. Subsequently others, including Frank Weber (Volt chief engineer, now BMW i3), used this information to create a mod that prevented ERDTT.

https://gm-volt.com/forum/showthread.php?127761-ERDTT-Modification-Options&p=1758281#post1758281

Regardless, I (and others) have been running this mod for years without issue. Chicago get plenty cold in the winter.
So the problem that simplex has reported five posts back with the grill shutters on the gen2, also has nothing to do with the modded sensor?

I won't do this mod on our 2018, until 100% convinced of no issues. ERDTT is to me, a minor irritation at worst, and the definition of a first world problem.

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So the problem that simplex has reported five posts back with the grill shutters on the gen2, also has nothing to do with the modded sensor?

I won't do this mod on our 2018, until 100% convinced of no issues. ERDTT is to me, a minor irritation at worst, and the definition of a first world problem.

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Not having a pre-2019 Gen 2 I have no personal experience to share on that. My experience and reference link posted are with Gen 1.

No one is forced or required to install a ERDTT defeat, to each their own. Mine works very well, glad I have it. YMMV.
 

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Not having a pre-2019 Gen 2 I have no personal experience to share on that. My experience and reference link posted are with Gen 1.

No one is forced or required to install a ERDTT defeat, to each their own. Mine works very well, glad I have it. YMMV.
Thanks. Guess I'll pass, now that I know that I am not being forced to do it.

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jcanoe is right, your issue with the battery wasn't related to the modded sensor this is just random badluck.

I had a Gen1 and now a gen2 volt for years and didn't have a problem with the modded sensor EXCEPT with the Gen 2, as soon the temps are below freezing temps, the check engine light will appear (Code P059F - active grille shutters not performing as expected) because the active front shutters will be stuck in ice and since and cannot open/close. The BCM receives a false temperature, it wants to operate the shutters thinking the temperature is OK to do so, but in fact, it's not. The BCM will not activate the shutters when it knows the temperature are at the freezing level thus preventing the CEL. This is the only problem I experienced with modded sensor.
We have to choose between getting the CEL and thus loosing the remote start function (at the moment we need it the most) or accept burning some fuel on very cold days. I know this is frustrating.

GM corrected this in the MY 2019 volt the ERDTT will operate only on very very cold days (-25 degrees Celcius is I recall correctly)
But I guess GM is unable to reprogram our "old" Volts to this value, which is something Telsa does with their products...

I live in Canada, so I feel your pain.
I did some reading online about active grill shutters. Although I was unable to find specific information about what activates them on a gen2 Volt, I did find info about how they operate on another vehicle.

What I found out, is that the shutters are controlled by the ECM, which takes in several inputs from sensors etc. Among those inputs, are ambient temperature.

The ERDTT defeat mod for pre 2019 gen2 Volts, functions by creating a false ambient temperature reading. It seems likely to me therefore, that it may cause the active grill shutters on the gen2 Volt to operate improperly. Even if it does not actually throw a code, the shutters may still be operating improperly.

Here is a quote from a description of how active grill shutters work on a Ford truck. I didn't find anything that is this detailed, specific to the gen2 Volt, but I wouldn't be surprised if they operate in a similar fashion.


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Here is a quote from a description of how active grill shutters work on a Ford truck.
I refer to the FORD F150 fluid specs when I consider anything for my Volt or Bolt. Also their lug nut torque setting. I mean, they are bound to be the same, right? :)
 

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I refer to the FORD F150 fluid specs when I consider anything for my Volt or Bolt. Also their lug nut torque setting. I mean, they are bound to be the same, right? :)
The example I gave was not about precise vehicle specific specs like lug nut torque. It was about the general operation of a system on a motor vehicle. The general operation of internal combustion engines is pretty much the same, the general operation of disc brakes....,etc. I just used an example that happened to be regarding a Ford truck, to illustrate the general operation of active grill shutters.

Shutters are being widely used to enhance aerodynamics, while at the same time providing sufficient cooling for the ICE. I have them on my 2011 Cruze Eco, as well as our 2018 Volt. It is logical to think that ambient air temperature would be a useful parameter regardless of make and model of an ICE equipped vehicle.

I was simply responding to a post by simplex who had a code thrown regarding the grill shutters after installing the ERDTT defeat on a gen2. My intent was to lend credence to the very real possibility that the ambient temperature sensor may not be just for the ERDTT, and the temperature readout on the information display.

This modification works by creating false ambient temperature readings. If this causes unintended consequences, such as improper operation of the active grill shutters, then I am not interested.
 

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I refer to the FORD F150 fluid specs when I consider anything for my Volt or Bolt. Also their lug nut torque setting. I mean, they are bound to be the same, right? :)
OK I found a description of GM active grill shutters. It clearly states that ambient temperature is a variable. Still not a gen2 Volt, but we are getting closer.

I am raising this not just for myself, but so any forum members contemplating this mod on a gen2, are aware of possible unintended consequences.

I am aware that this is a well sorted out mod for the gen1, but that lacks the shutters. This mod may be problematic on a gen2.


http://gmauthority.com/blog/gm/general-motors-technology/gm-aerodynamics-technology/gm-active-aero-shutters-technology/

From the above article:


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I am raising this not just for myself, but so any forum members contemplating this mod on a gen2, are aware of possible unintended consequences.

I am aware that this is a well sorted out mod for the gen1, but that lacks the shutters. This mod may be problematic on a gen2.
After going through the Service Manual, there appears to be a large number of (semi-redundant) sensors available to a small number of control modules, giving programmers a huge swath of variables/inputs they can choose from in controlling the car. So much so, that its hard to get a complete/precise story of how the electronics actually work.
 

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Why would the Volt's battery TMS rely on the OAT sensor and waste energy heating or cooling the battery when there are battery temperature sensors? Especially while the Volt is parked the battery temperature will change much slower than changes in the air temperature.
I'm not saying that it definitively does. My point is that the technical documentation is confusing and implies that it might be involved. (This is a theme all through the Factory Service Manual/Information... The mechanical stuff is well-covered and then when it gets to programmed features, we run into a dark curtain/cloud of mystery.)

To the OP's point, I definitely wouldn't bring up ERDTT defeat. Without clarity for GM technicians on the issue and how the batteries are taken care of in the cold, they can make whatever conclusion/trouble they want.

The Owner's Manual warns of conditions where the batteries may get too cold. It also has a number of places where is says the ambient air temperature sensor is just for the interior HVAC but there is another section "Electric Mode" that says that the engine will come on in instances where the battery is too hot or cold. It doesn't seem to be clear on which sensors it uses to determine this.

The Service Manual, under the DTC P0A9C-P0A9E Circuit Description says "... the battery temperature sensors to control the battery cooling system operation." However; in the Battery Cooling System Description, it says that the battery temperature sensors, coolant loop temperature sensor, A/C refrigerant temperature sensor, A/C refrigerant pressure sensor, and coolant level sensor to determine when to turn the system off. There's nothing that describes what commands the system on.


Does Frank Weber, Volt chief engineer count?
Not unless they were the ones who programmed this module. (If GM has their chief engineers working at this level of detail, then what little faith I have left in the company will be gone.)


Since I have the opportunity to lament on the topic again among friends, I wish GM had their engineers employed currently in providing 2019-ish software updates to the older cars, (like the lower ERDTT threshold) have a plug-and-play charger upgrade, have a pathway to upgrading the infotainment, finding/fixing manual typos, etc.

I hope they are all putting their talents to work on something new and special but fear that they are actually trapped in the GM HQ basement loading staplers and folding SUV brochures...
 

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Since I have the opportunity to lament on the topic again among friends, I wish GM had their engineers employed currently in providing 2019-ish software updates to the older cars, (like the lower ERDTT threshold) have a plug-and-play charger upgrade, have a pathway to upgrading the infotainment, finding/fixing manual typos, etc.

I hope they are all putting their talents to work on something new and special but fear that they are actually trapped in the GM HQ basement loading staplers and folding SUV brochures...
We can only hope, but alas you are probably right about the SUV brochures being a priority.

This paragraph from the GM Authority article, backs up what simplex said about why a code was thrown after installing the ERDTT defeat mod on a gen2. It is definitely something to be aware of for anyone contemplating this mod on a 2016-2018 Volt.


PS: Is the Service Manual you are referring to for a gen1 or gen2? Is it your belief that the ERDTT mod may even be a bit dodgy on a gen1, based on your reading of the Service Manual?
 

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PS: Is the Service Manual you are referring to for a gen1 or gen2? Is it your belief that the ERDTT mod may even be a bit dodgy on a gen1, based on your reading of the Service Manual?
It's a Gen2 (2018) Service Manual. I don't have access to any technical information about the Gen1, so I wouldn't know what sensors are in the pool or how they are described.
 

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We can only hope, but alas you are probably right about the SUV brochures being a priority.

This paragraph from the GM Authority article, backs up what simplex said about why a code was thrown after installing the ERDTT defeat mod on a gen2. It is definitely something to be aware of for anyone contemplating this mod on a 2016-2018 Volt.


PS: Is the Service Manual you are referring to for a gen1 or gen2? Is it your belief that the ERDTT mod may even be a bit dodgy on a gen1, based on your reading of the Service Manual?
Here is what I learned about ERDTT with my GEN1 and GEN2 volt with my personnal experience:

GEN1: I had no problem at all with the ERDTT mod. Lots of weeks at extremely cold temperature and the only thing that happened, was when the car was unplugged after a day at work, at an historical minus 40 degrees C, the Battery was too cold to operate (same icon on the DIC as when the battery is completely depleted), so the ICE started immediately and 10 minutes later the battery came back into normal state with all the energy bars from the morning when I arrived at work. Normal behaviour as per user manual about cold climate conditions. No real problem occured in 3 years.
Conclusion : GEN1 is more "ERDTT defeat friendly" as the GEN2.

GEN2: I do not recommand using the ERDTT defeat sensor because of the active air grille shutters behaviour that need a real temperature mesurement to operate properly without causing a fault. And if you are stubborn and absolutely want that ICE to stay shut on cold days, remember that you will have to ignore the Check engine light code P059F (and that will also disable the remote start feature). It will clear itself when the temperatures will be above freezing temps and the shutters will move as expected. Choose your battle.

And if you go to the dealership, don't forget to remove that thing if you don't want to void your warranty!!!;)

HTH
 
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