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Discussion Starter · #1 ·
I purchased the 1-4 shift lockout defeater before I picked up the car the museum intending to install it after I drove home. On a 2800 mile trip, not once did the car prevent me from shifting from 1st to 2nd to 3rd to 4th. Under all kinds of acceleration, spirited to great great grandmotherly. I hesitate to call this a problem because now I don't have to jack the car up to install the defeater, but something evidently must be wrong.

Anyone with similar experience or advice?
 

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Mine does the same thing. It might have to do with what mode you're in at the time. I though I read somewhere about the car skip shifting under a certain speed like 19 mph. Don't quote those figures, but something in the teens sticks out to me. Can you return the part you bought?
 

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Mine does the same thing. It might have to do with what mode you're in at the time. I though I read somewhere about the car skip shifting under a certain speed like 19 mph. Don't quote those figures, but something in the teens sticks out to me. Can you return the part you bought?
It should skip shift between 16 and 18 mph. Under or over that and it will not skip shift.
 

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Discussion Starter · #4 ·
It should skip shift between 16 and 18 mph. Under or over that and it will not skip shift.
So in other words, if I am not between 16 - 18mph when trying to shift from 1st to 2nd, then the lockout won't take place. If that's the case, putting in the defeater hardly seems worth the effort. Just shift to 2nd before 16 or after 18. What a goofy setup. That small window is what gave GM more "brownie eco points" to the EPA thugacracy?
 

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So in other words, if I am not between 16 - 18mph when trying to shift from 1st to 2nd, then the lockout won't take place. If that's the case, putting in the defeater hardly seems worth the effort. Just shift to 2nd before 16 or after 18. What a goofy setup. That small window is what gave GM more "brownie eco points" to the EPA thugacracy?
Exactly. I never get the 1-4 shift because I always shift from 1st to 2nd above 18 mph.
 

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I've simply never had the problem at any speed. Never understood why so many bloggers were buying that thing. Maybe GM just decided to stop annoying people after a certain VIN#.
 

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Discussion Starter · #7 ·
So ends the mystery burger. Class dismissed. Thanks all.
 

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I hope we can still explore this issue. Is it the mode? Is is something more complicated like operating temperature? Mine skip shifts all the time both before and after I am in the 20's mph. The only time it doesn't skip shift is when I am accelerating aggressively. I don't like to do that when the engine is cold, however. Anyone else have my experience? I really don't like the skip shift. Does installing the defeater cause warranty problems? Or am I missing a more simple solution to avoid the skip shift? Where did you get the information that says the skip shift is only operative between 16-18 mph? The owners manual recommends that a 1-4 shift should be made at 27 mph.
 

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TPS (Throttle Positon Sensor) 28% or more will disable skip shift. C.A.G.S is GM way of saying skip shift, (Computer Aided Gear Selection aka Skip Shift). (Vehicle Speed Sensor), VSS has to do with reverse lockout, reverse lockout is enable at speed above 3.0 mph.
 

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Discussion Starter · #12 ·
So the way I understand this software depiction:
- CAGS is disabled when-
- Throttle > 28%
- Coolant > 171 F.
- Speed > 19mph
- Barometric pressure > 76 KPa but < 78 KPa

Correct? Thanks much for posting this!
 

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I would think the coolant one would be "<" instead of ">", right?
 

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Discussion Starter · #14 ·
I would think the coolant one would be "<" instead of ">", right?
I suppose you're right the more I look at it. I guess the readout means that CAGS will kick in above that coolant temperature.

So, guess I bought a stupid $25 device for nothing, since the receipt is long gone. Oh well, saved me from having to pull out my jack and four stands.
 

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Tables shown tell us:
CAGS disable if TPS is over 28%
CAGS disable is coolant temp is below 171 deg F
CAGS disable if speed is over 19 mph
and finally the barometric pressure must be between 76 and 78 kPa

Another way to look at it is:
CAGS will be enabled only if the following set of conditions (all of them) are met when shifting out of first gear:
TPS below 28% (heavy foot - no CAGS)
Coolant temp above 171 deg F (cold engine = no CAGS)
Speed below 19 mph (high speed = no CAGS)
and finally the barometric pressure must be between 76 and 78 kPa
 

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I have some questions for those who have installed the 1-4 skip shift defeater. Do you think installing that will cause warranty issues? Do you still get the Skip Shift message on your display, or do you get any error messages? Does installing the defeater also cancel the reverse lockout protection? Am I correct in assuming my dealer won't want to do this? Where did you get yours installed if you didn't do it yourself? Thanks!
 

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The message stills shows on the display and on the heads up display.
Don't know about warranty.
I can shift back and forth between 6-7 and really haven't paid any attention to the reverse lockout. Rev matching still works.
My floor jack, an aluminum racing jack, lifts the car high enough to change wheels but not high enough to crawl under the car. I had a local auto repair shop do the install. It took them longer to raise the car than install the CAGS eliminator. They actually did it for free since it was the first C7 anyone had seen. However, I have used them for car repair over the last 15 years. Any reputable car repair shop can do this. You just need to get your hands up into a tight space and unplug an electrical connector. Easy if the car is on a lift but more difficult if you are laying on your back under the car.
 

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Also, I suggest getting your own set of lifting pucks. Many shops don't have the smaller sized pucks for the C7.
 

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I had my dealer I purchased the car from install mine. They charged me $45 to install it while they were fixing a rear hatch seal under warranty. The message still comes on. We have a lot of bumper to bumper traffic and my message comes up quite a bit due to that, so I am glad I have it. If you don't have a lot of slow driving you probably don't need it.
 

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This was one of the best and easiest mods I've ever done on a car. Installed it myself while I had the car up for its first (1,500 mi.) oil change. After install I would get the message on the DIC every now and then but could continue to 2nd. I must have changed my driving habits a little because I haven't noticed the message in a while.

The skip shift makes you feel like a dummy. All it takes is one time and your mood will change. Nip it in the bud.
 
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