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With winter approaching and a relatively nice day, I decided to install my modified ambient outside air temperature sensor. It has a small 1/8W, 39k Ohm resister wrapped around the two sensor poles. This resistor tricks the sensor to see a higher temperature than actual. The result: the Volt always thinks it's about 40°F outside even if it's -10°F.
Why did I do this?
So my gas engine doesn't run 2-3 times on a short trip to a store or restaurant even though my battery is fully charged and the car interior is warm. This is called Engine Running Due to Temperature (ERDTT). GM decided that they would run the gas engine for you when it gets cold outside. Even if you don't want or need it to run. My 2011 initiates ERDTT when the outside temps hit 15°F or below (I think the 2019 allows the ERDTT to be set to -13°F).
With ERDTT, it doesn't matter if my car is already warm and cozy, it doesn't matter if I have enough battery to warm the cabin for my trip. Chevy decided it's going to run the engine anyway, wasting gas to create cabin heat that I don't need. Hence, the ERDTT defeat sensor.
This will be the second year I have used the modified sensor. The only downside is you won't know what the actual outside temperature is.
My install process is to drive the front tires up onto two, stacked 2" x 12" x 36" boards, one set of these "ramps" for each wheel. This raises the front nicely. Engage parking brake, chock the rear wheels.
Using my scissors jack under the front passenger lift point, I raised the car, but not all the way. Loosened the wheel lug nuts, raised the wheel off the wood ramp, removed the wheel. I placed a three-legged jack stand under the jacking point, lowered the scissors jack so the car was now resting on the three legged jack stand as well.
I removed the three 8MM bolts on the skid plate mounted to the underside of the engine area. Removed the 5, 7MM bolts holding the small air dam wing and the first 2 7MM bolts of the longer air dam. Removed the entire fender liner (#2T Torx bit and a small, flat bladed screw driver for to plastic pop rivets). Set aside the wheel liner (it includes the skid plate). Lots of access to the car's underside now. No fighting plastic pieces, scraping my wrists or working blind.
The black air temp sensor with blue connector is located above the 7th air dam bolt, and is press fit into the plastic housing that surrounds the front air intake louvers. I basically twisted it a bit and pulled it out. Using a small, flat bladed screwdriver I gently pried to long black clip running down one side of the sensor, releasing the sensor from it's blue connector. I was careful not to lose the gray, ribbed water/dirt seal.
Plugged in my resistor-equipped replacement. Reassembled.
Resistors https://www.amazon.com/NTE-Electronics-EW339-Flameproof-Tolerance/dp/B008UTY0RC
Related threads https://gm-volt.com/forum/showthread.php?127761-ERDTT-Modification-Options
https://gm-volt.com/forum/showthread.php?308145-Engine-running-during-winter
Will it void my warranty? No
Doesn't the battery need this for it's warming system? No
With this in, what if I want the engine to run? Put it in Hold or Mountain mode depending on your year.
Why did I do this?
So my gas engine doesn't run 2-3 times on a short trip to a store or restaurant even though my battery is fully charged and the car interior is warm. This is called Engine Running Due to Temperature (ERDTT). GM decided that they would run the gas engine for you when it gets cold outside. Even if you don't want or need it to run. My 2011 initiates ERDTT when the outside temps hit 15°F or below (I think the 2019 allows the ERDTT to be set to -13°F).
With ERDTT, it doesn't matter if my car is already warm and cozy, it doesn't matter if I have enough battery to warm the cabin for my trip. Chevy decided it's going to run the engine anyway, wasting gas to create cabin heat that I don't need. Hence, the ERDTT defeat sensor.
This will be the second year I have used the modified sensor. The only downside is you won't know what the actual outside temperature is.
My install process is to drive the front tires up onto two, stacked 2" x 12" x 36" boards, one set of these "ramps" for each wheel. This raises the front nicely. Engage parking brake, chock the rear wheels.
Using my scissors jack under the front passenger lift point, I raised the car, but not all the way. Loosened the wheel lug nuts, raised the wheel off the wood ramp, removed the wheel. I placed a three-legged jack stand under the jacking point, lowered the scissors jack so the car was now resting on the three legged jack stand as well.
I removed the three 8MM bolts on the skid plate mounted to the underside of the engine area. Removed the 5, 7MM bolts holding the small air dam wing and the first 2 7MM bolts of the longer air dam. Removed the entire fender liner (#2T Torx bit and a small, flat bladed screw driver for to plastic pop rivets). Set aside the wheel liner (it includes the skid plate). Lots of access to the car's underside now. No fighting plastic pieces, scraping my wrists or working blind.
The black air temp sensor with blue connector is located above the 7th air dam bolt, and is press fit into the plastic housing that surrounds the front air intake louvers. I basically twisted it a bit and pulled it out. Using a small, flat bladed screwdriver I gently pried to long black clip running down one side of the sensor, releasing the sensor from it's blue connector. I was careful not to lose the gray, ribbed water/dirt seal.
Plugged in my resistor-equipped replacement. Reassembled.
Resistors https://www.amazon.com/NTE-Electronics-EW339-Flameproof-Tolerance/dp/B008UTY0RC
Related threads https://gm-volt.com/forum/showthread.php?127761-ERDTT-Modification-Options
https://gm-volt.com/forum/showthread.php?308145-Engine-running-during-winter
Will it void my warranty? No
Doesn't the battery need this for it's warming system? No
With this in, what if I want the engine to run? Put it in Hold or Mountain mode depending on your year.