General Question

rojo's avatar

How do power tailgate lifts work?

Asked by rojo (15988 points ) February 4th, 2013

In the parking lot this morning I saw a tailgate on a GMC Yukon open up automatically. There was no one around the vehicle or in it. It stayed open for less than a minute then closed down again. The only other thing that could have been related to it was someone getting into their car about six parking spaces down. They used an auto-unlock on their keychain as they approached their vehicle. Their lights flashed and it went “beep…beep”. They got in and drove off. It was during this time that the unattended Yukon tailgate did its’ thing.
I assume it is possible that two different vehicles use the same frequency for similar operations but how common or uncommon would this be?

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7 Answers

elbanditoroso's avatar

Absolutely. The signal from the key fob to the back of the vehicle is a radio signal, just like a cell phone or walkie talkie . The number of channels/frequencies is limited. Even if General Motors assigned some sort of digital address to each vehicle (and each key) there is always the possibility of duplication.

It’s basically the same idea with car keys – there is a finite number of key shapes (ridges and valleys) that can be cut on a traditional key. I don’t remember what it is, but I believe it’s under 100,000. GM sells 4 million cars a year. So you have to figure that one out of every 40 GM cards has the same key shape. The trick is knowing which one…

Another alternative is that someone in the lot had a badly tuned radio transmitter and was spewing their signal across many frequencies. Somewhat of a long shot, but possible.

jerv's avatar

They all use the same frequency, but a different serial number. The odds are pretty slim that two vehicles would share the same one as, unlike physical keys, there are many more possible serial numbers.

Adirondackwannabe's avatar

The number of key patterns is 1000, so I’m guessing a lot of crossover happens. I once had a guy with a Buick unlock my Chevrolet when I accidently locked me keys in it.

LuckyGuy's avatar

It depends upon the year. Back in the “stone age” they broadcasted an audio tone on top of the main carrier frequency. That was very limiting. 32 tones So they improved and broadcasted a DTMF tone like telephones. That made more choices 1000. then they went to 16 bit digital with 65,656 choices. Car were still ripped off so they went to 32 bits with billions of choices. But the bad guys learned to record the signal and play it back to open the doors. (Slimebags) To fix that, the code now rolls through a complex pattern so it is different every time. That is why your key fob sometimes gets out of synch.
Now the bad guys just break the glass.

Tropical_Willie's avatar

They have been making power liftgates on GMC Yukon for only 10 years or so. That would be at the point of rolling code being used.
May have been a “OOPS” by the owner just out of eyesight.

WestRiverrat's avatar

One of the auto dealers here had a car give away here recently, and they had prepicked the winner. They were very surprised when someone started the car with a ‘nonwinning’ key. Wouldn’t have been a problem but they tried to tell the guy that started the car he wasn’t the winner. He turned out to be an attorney and ended up winning not just the car but a substantial settlement for the rigged game of chance.

There are only so many frequencies available that there is bound to be some duplication.

Buttonstc's avatar

answered in wrong thread. Sorry. iPhone blindness.

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