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Discussion Starter #1 (Edited)
For those aggravated by the ICE running during short trips in the winter months, there are a few mods for preventing or delaying ERDTT. Note that employing some of these mods may or may not cause warranty issues if there is a problem later on.

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 and Tboult. Subsequently others, including Frank Weber (Volt chief engineer, now BMW i3), used this information to create a mod that prevented ERDTT.

1.Resistor Method
This relies on tricking the air temp sensor into seeing a higher temp by adding a 1/8W 39K Ohm resistor between the two sensor pins and therefore prevent ERDTT.
Air Temp Sensor with Resistor.jpg

See https://gm-volt.com/forum/showthread....98#post1140098 and

See https://gm-volt.com/forum/showthread....86#post1140786

Frank Weber (Volt chief engineer, now BMW i3) also posted his personal mod along these lines. http://roulezelectrique.com/recalibr...re-de-la-volt/ (use Google Chrome browser for auto-translation) The method does appear to work.

Variation 1: Switched Resistor Under Hood
Rather than attaching the resistor directly to the sensor, attach it via a switch under the hood

See https://gm-volt.com/forum/showthread....33#post1506433

New version was here (seems to be gone now): http://www.ebay.ca/itm/Sonde-tempera.../281246258931?
New link: http://www.ebay.com/sch/i.html?_odk...Volt.TRS0&_nkw=ERDTT+Volt&_sacat=0&rmvSB=true
Also see https://gm-volt.com/forum/showthrea...tic-ERDTT-disabling-Add-on-modules-availables...

Variation 2: Switched Resistor in Cabin
You don't need to access/replace/modify the sensor itself. Add the resistor with a switch in the passenger compartment by locating the appropriate wire pair. The air temp sensor is a two-wire circuit that runs from the bumper-mounted air sensor pins, through the right side underhood area, then through the front bulkhead pass-through to the HPCM2 (Hybrid Hybrid Powertrain Control Module 2 X1) module under the front passenger seat. The circuit could be accessed and modified with a resistor anywhere between those end points.

Pin Size Color Circuit Function
26 0.35 L-BU/GY 636 Outside Ambient Air Temperature Sensor Signal
40 0.35 BK/L-BU 61 Outside Ambient Temperature Sensor Low Reference


LugNuts Implementation thread: https://gm-volt.com/forum/showthread.php?328361-All-I-want-for-Christmas-is-no-ERDTT
Resistance testing discussion by WOT and TBoult here: https://gm-volt.com/forum/showthread....-..-quot/page3

2. Covered Sensor Method
The other method is to simply slow the temperature sensor by blocking it from direct wind.

Cover the sensor or the air intake grills with 1/2 " foam pipe insulation or cardboard to keep it out of the direct wind. This will delay ERDTT but will not stop it. One who tried closing the air space between the intake grills with the pipe insulation reports: 25-30% reduction in gasoline consumption in ERDTT mode ( 2,25 l/100km to 1,75 l/100km ). because the ICE simply cycles less frequently. Testing was done on the same route every day, 130 km (81miles) per day. “No check engines, nada problems.”

See https://gm-volt.com/forum/showthread....42#post1143442

and https://gm-volt.com/forum/showthread....26#post1191426

and https://gm-volt.com/forum/showthread....50#post1514650

Reference Posts:
https://gm-volt.com/forum/showthread....n-Kit-Aero-Mod.
https://gm-volt.com/forum/showthread....42#post1143442
https://gm-volt.com/forum/showthread....-winter-Anyone
https://gm-volt.com/forum/showthread....86#post1140786
https://gm-volt.com/forum/showthread....98#post1145498
http://roulezelectrique.com/recalibr...re-de-la-volt/
https://gm-volt.com/forum/showthread....-..-quot/page3
 

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Awesome!

Variation 2: Switched Resistor in Cabin
You don't need to access/replace/modify the sensor itself. Add the resistor with a switch in the passenger compartment by locating the appropriate wire pair. The air temp sensor is a two-wire circuit that runs from the bumper-mounted air sensor pins, through the right side underhood area, then through the front bulkhead pass-through to the HPCM2 (Hybrid Hybrid Powertrain Control Module 2 X1) module under the front passenger seat. The circuit could be accessed and modified with a resistor anywhere between those end points.

Pin Size Color Circuit Function
26 0.35 L-BU/GY 636 Outside Ambient Air Temperature Sensor Signal
40 0.35 BK/L-BU 61 Outside Ambient Temperature Sensor Low Reference

Resistance testing discussion by WOT and TBoult here: http://gm-volt.com/forum/showthread....-..-quot/page3
GREAT POST!!!

I am EXTREMELY interested in doing the quoted method, but would love someone to do a step by step with materials and pictures to help me along. Is anyone willing to do this? I will offer help in any way i can with documenting/feedback along the way. I think this is the best method to perform this modification.
 

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Discussion Starter #3
for future use
 

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GREAT POST!!!

I am EXTREMELY interested in doing the quoted method, but would love someone to do a step by step with materials and pictures to help me along. Is anyone willing to do this? I will offer help in any way i can with documenting/feedback along the way. I think this is the best method to perform this modification.
I agree, the in-cabin switched method seems best. I'm considering doing instructions etc. and selling a kit, unless someone beats me to it, which is okay too. :)
 

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Although I began last winter with a fixed resistance in place of the Ambient Air Temp Sensor, I did actually change over to the Volt chief engineer's above cited method of putting a resistor in parallel inside the actual B9 sensor.

Had to source a much smaller 1/8 watt resistor since anything bigger wouldn't fit correctly into the sensor and still be able to plug it fully into the connector as well as getting hold of the proper wire wrap tool in order to get this tiny resistor to fit snugly onto the sensor's pins.

Tried using a 33KΩ resistor as well as 47KΩ. Both gave a positive offset reading on the center stack touchscreen via the Hybrid/EV powertrain control module 2 K114A. 33KΩ gave a much higher offset than 47KΩ but I ended up settling on the lower offset 47KΩ resistor and this along with selecting the 'cold' to 'very cold' setting my Volt ran just fine that way for the rest of the entire winter w/o issue and with absolutely no ERDTT events!;)


Ambient Air Temperature Sensor - GM (25775833)

BTW: If anyone is interested in ordering the above B9 sensor online or sourcing it from the parts dept of your local dealership, you could then shoot me a PM and we could work it out to where you could mail me this sensor, I then add the resistor in parallel since I have the proper wire wrap tool (your choice of offset either 47KΩ or 33KΩ depending on your climate/needs) and I would mail you back a modified & ready to install B9....
 

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Although I began last winter with a fixed resistance in place of the Ambient Air Temp Sensor, I did actually change over to the Volt chief engineer's above cited method of putting a resistor in parallel inside the actual B9 sensor.

Had to source a much smaller 1/8 watt resistor since anything bigger wouldn't fit correctly into the sensor and still be able to plug it fully into the connector as well as getting hold of the proper wire wrap tool in order to get this tiny resistor to fit snugly onto the sensor's pins.

Tried using a 33KΩ resistor as well as 47KΩ. Both gave a positive offset reading on the center stack touchscreen via the Hybrid/EV powertrain control module 2 K114A. 47KΩ gave a much higher offset than 33KΩ but I ended up settling on the lower offset 33KΩ resistor and this along with selecting the 'cold' to 'very cold' setting my Volt ran just fine that way for the rest of the entire winter w/o issue and with absolutely no ERDTT events!;)


Ambient Air Temperature Sensor - GM (25775833)

BTW: If anyone is interested in ordering the above B9 sensor online or sourcing it from the parts dept of your local dealership, you could then shoot me a PM and we could work it out to where you could mail me this sensor, I then add the resistor in parallel since I have the proper wire wrap tool (your choice of offset either 47KΩ or 33KΩ depending on your climate/needs) and I would mail you back a modified & ready to install B9....
Hi Somms,

Just thinking aloud here, I personally prefer installing the switch under the passenger seat. That way it could be easily accessed whenever someone wanted to disable it. I may still pursue such an option, after determining how hard it is to remove the seat in the first place. ;)
 

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Discussion Starter #8
Needs a sticky maybe Steve?
It's in the sticky note index in this "Chevy Volt Accessories and Modifications" sub-forum, Mister Dave. Almost every forum and sub-forum has one sticky note with an index to other "sticky items" that are not technically sticky notes. People complained that the number of individual sticky notes took up too much room on the forum topic list. So now there is just one per forum, a compilation index.
 

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Although I began last winter with a fixed resistance in place of the Ambient Air Temp Sensor, I did actually change over to the Volt chief engineer's above cited method of putting a resistor in parallel inside the actual B9 sensor.

I ended up settling on the lower offset 33KΩ resistor and this along with selecting the 'cold' to 'very cold' setting my Volt ran just fine that way for the rest of the entire winter w/o issue and with absolutely no ERDTT events!;)
Just to be 100% clear...
You're using the OEM sensor and a 33kΩ resistor wired in parallel between the two sensor leads?
 

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Just to be 100% clear...
You're using the OEM sensor and a 33kΩ resistor wired in parallel between the two sensor leads?
Correct, I have a 1/8 Watt resistor parked inside the sensor so the only part actually modified is the sensor itself...
 

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Correct, I have a 1/8 Watt resistor parked inside the sensor so the only part actually modified is the sensor itself...
Excellent- thank you!
Does this mod affect the OAT reading we see on the center stack?
Is there a reason to remove the mod for summer use?

Thanks....
 

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Excellent- thank you!
Does this mod affect the OAT reading we see on the center stack?
Is there a reason to remove the mod for summer use?

Thanks....


As an example, the above pic shows the temp diff between B9 modified w/47KΩ in parallel center stack touchscreen readback and the actual measured temp as displayed by the acurite indoor/outdoor thermometer (outside temp in blue w/transmitter mounted directly above radiator).

Keep in mind the parallel resistance added to the sensor would have a non-linear effect on the touchscreen temp readback offset. At 15F, the offset would be more positive and as the outside temp climbs this offset difference would become less and less. So to answer your question leaving the modified sensor in during the summer is yes, you can and the amount of error would be much less than during very cold temps...
 

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Here's a question... Last year, many people saw a mode where the engine ran in a different mode, because the car was much colder than the ERDTT threshold. In this mode, energy into and out of the battery was reduced as much as possible. If someone modifies this sensor as described, will that prevent this other mode from being entered?

That would be bad.
 

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So to answer your question leaving the modified sensor in during the summer is yes, you can and the amount of error would be much less than during very cold temps...
Thanks again somms!
Being I'd like accurate summer readings, I could permanently connect one resistor lead to one sensor wire under the seat, then use a spade "T" tap connector to connect the other resistor (with a spade) lead to the other sensor wire under the seat for winter. It would take a full 5 seconds to connect or disconnect it when desired.
 

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Here's a question... Last year, many people saw a mode where the engine ran in a different mode, because the car was much colder than the ERDTT threshold. In this mode, energy into and out of the battery was reduced as much as possible. If someone modifies this sensor as described, will that prevent this other mode from being entered?

That would be bad.

Very good question and I'm not 100% sure but I would think that specific reported mode that also gave no corresponding readback either on the Driver Information Display unlike ERDTT may have more to do with the set of 16 individual temperature sensors attached to the top of the Li-ion batteries...
 

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Discussion Starter #16 (Edited)
Thanks again somms!
Being I'd like accurate summer readings, I could permanently connect one resistor lead to one sensor wire under the seat, then use a spade "T" tap connector to connect the other resistor (with a spade) lead to the other sensor wire under the seat for winter. It would take a full 5 seconds to connect or disconnect it when desired.
The purpose of an ERDTT switch would be to switch between "resistor/no resistor" Switched to "no resistor" the system operates normally. Switched to "resistor" the current is shunted through a resistor, artificially raising the air temp the sensor reads. No need to plug and unplug. That way, on very, very cold days, switch it off and the car will run ERDTT like always. But for a quick 10 min drive to the store, switch the resistor on so your car does not do ERDTT by the time you finish backing out of the garage!
 

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http://www.omega.com/temperature/Z/pdf/z256-257.pdf

You can see the resistor values from the 44034 part (If I remember correctly). Anything under ~20Kohm will disable ERDTT (on 2012). If you want to enable ERDTT, but move the setpoint to lower weld another one in parallel (ERDTT would be at -17'C).
 

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The purpose of an ERDTT switch would be to switch between "resistor/no resistor" Switched to "no resistor" the system operates normally. Switched to "resistor" the current is shunted through a resistor, artificially raising the air temp the sensor reads. No need to plug and unplug. That way, on very, very cold days, switch it off and the car will run ERDTT like always. But for a quick 10 min drive to the store, switch the resistor on so your car does not do ERDTT by the time you finish backing out of the garage!
Need to be careful with the unplugging or plugging in of the sensor or any switch in or switch out times because if B9 is unplugged for a significant amount of time @30sec , the Hybrid/EV powertrain control module 2 K114A will interpret this open as max resistance, the touchscreen will defaiult to -40F when the Volt is turned back on and the ICE will begin running immediately. It takes well over an hour for B9 to recalibrate and begin displaying the proper readback if it is disconnected long enough to default to -40F...
 

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Thats interesting. On a 11-12 you could force the engine on with a resistor. My question would be would just the engine running prevent most electrical power from the battery from going to the drive motor?
 
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