A question about throttle by wire. - Team Camaro Tech
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post #1 of 10 (permalink) Old Dec 18th, 07, 08:04 AM Thread Starter
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A question about throttle by wire.

I have been curious and thought I would throw this out there.
I know sensors and other misc electrical components don't function properly on occasion. And sometimes need replacement. But sometimes the reason they fail is "unknown".
I wonder what would happen if these throttle by wire devices should one day become faulty too.
Does the car shut down, or is it possible to WOT? Or what happens?

I know most new vehicles are TBW, I am more curious about the aftermarket though.


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post #2 of 10 (permalink) Old Dec 18th, 07, 08:28 AM
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Re: A question about throttle by wire.

Shortly after I bought it, the drive by wire "gas pedal" went out (I don't think it went completely out, but out enough to set errors) in my Silverado.

A warning light came on on the dash, and the info display said "reduced engine power."

The thing still ran, and sorta responded to the accelerator, but VERY slowly. I drove the 15 miles back to the dealer at about 20 mph....
It was near noon on a Saturday. They reset the code and "all was well." I drove around near the dealership for about a half hour before it happened again. This time they said they had to replace the throttle assy, and would order it on Monday. I suggested that as I've been buying new cars and trucks from this dealership for over 10 years, and I had just bought this truck the day before, perhaps they could do better. They pulled the gas pedal out of a new silverado on the lot and swapped it, been fine ever since.





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post #3 of 10 (permalink) Old Dec 18th, 07, 03:20 PM Thread Starter
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Re: A question about throttle by wire.

That's kind of what I expected to happen to a new one.

I wonder if the aftermarket or "modified" factory units could malfunction in different ways.

Sort of like the carb linkage/engine mount breakage WOT problem....


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post #4 of 10 (permalink) Old Dec 18th, 07, 07:15 PM
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Re: A question about throttle by wire.

with app1 and 2 needing to correlate..a fail safe is in place.Throttle angle is limited and results in a limp home mode.As for the aftermarket..do they even offer up a throttle body compatible with an app sensor to date??

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post #5 of 10 (permalink) Old Dec 19th, 07, 06:15 PM
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Re: A question about throttle by wire.

Most of the gm app sensors are a double or triple redundant sensor. They are all fed with a 5 volt reference. however each "leg" of the sensor, has a different corresponding range that the ecm looks for if one of these signals is out of range it sets the code letting you know that there is an issue and that you need to have it corrected. The reduced power is there mainly for safety. As for the wide open issue the computer also looks at engine load, vehicle speed, and rpm, and knows enough to realize that the vehicle is not actually at wot, it then basically negates the reading coming from the sensor and kicks it into reduced power.

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post #6 of 10 (permalink) Old Dec 20th, 07, 12:13 AM
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Re: A question about throttle by wire.

That is right, it should neer fail to anything but idle according to what GM says, but from personal experience They Ain't Telling it All. I had I think a Colorodo come in the dealeship around the first of the year and after being driven for a while the customer said he the engine would begin to pull harder and harder. Eventually it would get to the point of having to hold the brake hard at a stop light. My first impression was the same as said above, according to SI this is impossible. After checking it over the throttle body was causing the problem but it DID NOT fail to idle as designed. A lot of development goes into this stuff but fly by wire will never beat a cable driven throttle, period.
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post #7 of 10 (permalink) Old Dec 20th, 07, 12:56 AM
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Re: A question about throttle by wire.

My wifes Volvo V70R did this, actually it's a major issue with Volvos and they "sort of" recalled them, basically paying for the part and you pick up labor, it was the throttle bottle end of it that failed, a 700$ part. It went into a limp home mode, where it had little or no power but still ran (imagine getting out into a busy road and this happens....)
Volvo sucks for recalling stuff we found out, and there is lots that failed on the car, some stuff time and time again. Did I mention we don't have the car anymore?

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post #8 of 10 (permalink) Old Dec 20th, 07, 05:20 AM
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Re: A question about throttle by wire.

Quote:
Originally Posted by tumper View Post
A lot of development goes into this stuff but fly by wire will never beat a cable driven throttle, period.
Here, here, give the man a beer, er, drink.

Give me back a mechanical means of throttle action whether stuck open or closed. Definitely alot faster than any computer read inputs making decision after looking up from a table driven device - alot faster.

But, its part of Traction/Stability Control system.

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post #9 of 10 (permalink) Old Dec 20th, 07, 05:26 AM
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Re: A question about throttle by wire.

The 2000ish F-350 7.3 diesels were prone to accelerator pedal failure.

I practice 'get Tim's butt home' preventive maintenance. I know all the guys at Ford. I bring my truck in and ask the old guys "What craps out?". They know the routine. Whatever the failure of the vintage may be... my truck gets a new one and my old part(s) get a tour of the US as part of my 'get home' strategy. And it has gotten my butt home more than once. Done cam sensor twice(always crap out when it is DAMCOLD and DARK), fuel injector harness connector under the valve cover once on the side of the road 20 miles north of Abilene. A turbo air pipe hose over by St. Louis on an interstate off ramp. Never had to replace my gas pedal...but I had one. You CAN fix newer cars. But you can't do it without knowledge, tools and parts.

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post #10 of 10 (permalink) Old Dec 20th, 07, 06:36 AM Thread Starter
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Re: A question about throttle by wire.

I know what you mean about the "cam" sensor. I had that thing drop out on me on my 02 Powerstroke crew 4x4 while towing my boat, I was coming up on a sharp turn and was just about to start on the brakes and begin the turn, and then instantly "OUT".... nothing, no engine, no power steering, no p/brakes, no gauges. VERY lucky for me there was noone coming around the curve at me because I had to coast REAL wide without those. Not something I will ever forget.
I knew what the truck was supposed to do when that sensor did its job, but I didn't know it was going to happen at the worst possible time. I do know it was also drive by wire.
I bought the truck new with 3 miles on it, and sold it with just a touch over 80,000 and this was the only problem I ever had with it.

This is one of those instances that makes me fear these "sensors" on all levels. And now even more so on a throttle.

Where exactly are all these safety switches and sensors made anyway?


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