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Discussion Starter #1
A few weeks ago my work installed charging stations, and I haven't used gas for daily driving since.

Flash forward, wife and I were going to a wedding on Saturday, using Hold mode on the highway when the check engine light comes on, cruise control shuts off, and I get a message on the dash "Propulsion Power is Reduced". Used the Onstar button and was told it was throttle position error (checked code when I got home, P2135). Called the dealer and made an appointment to drop off today. They told me I would be fine to finish my trip (9 miles to the wedding, and 30 miles home). The car drove fine, but the ICE was running even when I was driving in Normal mode, and the battery was depleting. When the battery was empty the ICE revved very high, and the car slowed to a stop. Luckily at that point I was off of the highway and about 3 miles from home. I turned off the power and restarted the car. The message was not there, and I was able to drive the rest of the way home. I charged the car fully, and drove it to the dealer this morning without issue. Just got the call that it was the throttle body and would need to be replaced. Total is $350+tax, and will be here done tomorrow.

Car has 42k miles, and although obviously the throttle body is attached to the engine, and very much integral to it's function, it is not considered to be part of the powertrain so it is not covered by any warranty. I am tempted to get the car back and replace the throttle body myself (it is only $99 on gmpartsdirect.com), but I am going to call the Volt Advisor today when they are available, and see if there is anything they can do for me. This is not a normal wear item, or part of general maintenance, and I would not expect to have to replace a throttle body at 142k miles let alone at 42k.

Anyone else have faulty throttle bodies?

I was just giving my Volt sales pitch to some co-workers last week, and they asked if people were concerned with issues with electric drive components and if that is what is driving down the prices on the used market. I told them how they were largely very reliable. Ironically mine has an issue with the ICE a few days later, not anything to do with the electric drive haha.
 

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My understanding is the Volt always operates wide open throttle, so not sure what it would use the throttle body for, but maybe it still has throttle plate. Don't know, but I would check with that Volt advisor.
 

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Discussion Starter #3
It doesn't always operate at WOT, it will vary, but tries to run at it's most efficient load. I called the Volt Advisor and they have opened a case and are looking into it. I will update with any more info.
 

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When I had my 1995 Buick Regal (I bought it in December 1994 and sold it last year after 21 years of great service), it gave me a similar "throttle position error". I discovered that there is a small sensor attached externally to the rotary throttle valve. Since I have the GM service manuals, I checked the resistance across the sensor (similar to a variable resistor used in volume controls) and it was open. A replacement cost me only about $15, but it was very troublesome to reach the sensor, remove it, and replace with a new one.

So I believe that the high cost is the labor to replace the throttle position sensor. If you can't get it replaced under warranty, either ask for a discount (having a great customer relationship with your dealers helps a lot as it does for me), or try to read the service manuals and understand the steps (and tools) to replace it yourself. Definitely it is a part of the gasoline engine, not the electrical drive system, and the ECU (Engine Control Unit) needs this sensor to determine the exact TPS (Throttle Position Sensor) signal and regulate the engine RPM to control the emissions and power output. In my case the faulty sensor allowd me to keep running but wasting more gasoline (and emit more emissions) than normal.
 

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I can't remember anything like this but I don't see everything and I don't remember everything I do see. I don't see this as being particularly an electric car problem, which I guess is the reason it's not considered part of the drive train. Definitely contact the Volt Advisor.

I have had zero problems with my 2011 MY, but these kind of issues are what made me get an extended service plan. One good thing is that the Volt is a Chevy, which means it comes with Chevy service pricing. If this were a luxury brand you'd need to add a "1" or even a "2" in front of the price. Don't ask me how I know!
 

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Not sure if this is related, but I know in my service history records the PO performed some sort of throttle body cleaning a couple times at the recommendation of their SA, and it's recommended again for the upcoming service.
 

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Discussion Starter #7
The sensor is not a separate item any more. You used to be able to replace them, and even adjust them, but not any more, they are integral to the throttle body. I think this happened around when they started using servo motors for the throttle by wire.

It is not an electric car problem, but the Volt actually has two powertrain warranties, one for the general powertrain, just like all GM vehicles (5 yr/100k miles) and one specific to the electric drivetrain, battery, controllers, etc. (8 yr/100k miles). Based on the warranty information that I read, sensors are not covered on the powertrain warranty, which seems ridiculous to me, but that is their policy. I am still going to keep fighting, because regardless of if they should be covered or not, you shouldn't have to replace the throttle body on a car with 42k miles, especially a car like a Volt that does not use the gas engine most of the time (In my case there are only 16,687 miles on the gas engine.)
 

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Dont jinx me. I have a 2014, 31k miles and about to go to a wedding in a couple of weeks! haha
 

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I've never actually had or personally heard of a throttle body failing before this one. It's been a while since I worked on cars, but from what I remember one sensor failing isn't supposed to cause a total failure. You should have the...
Throttle Position Sensor
Mas Air Flow Sensor
Air Pressure Sensor
02 Sensors

Between these, you should be able to lose one and still work well enough to drive.
 

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Discussion Starter #11
The failure is still a sensor, but they are not removable from the throttle body so the whole thing needs to be replaced.

Don't forget now there is no linkage between your pedal and the throttle body, it is all electronic. A sensor in the pedal tells a motor in the throttle body how much to open the throttle blade. There is a sensor in the throttle body as well that basically double checks the position in the throttle body follows what the pedal/ECU are requesting. If there is a condition which those two are not in sync you could easily restrict the engine speed basically to an idle (or WOT, but I would assume they fail safe to idle).

Yes in the "old" days you could lose a sensor and still work in limp mode, but things are a little different now.
 

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Discussion Starter #12
Got the car back last night. It was fixed under warranty. They say the throttle body is covered by the emissions warranty (throttle position sensor is listed as an item covered in the manual). Let this be a lesson to anyone else that has a similar issue. Don't know if it was the Volt advisor talking to the dealer that helped them realize their error, but it couldn't have hurt. Glad we have that resource available to us.
 
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