Can key fob open up different cars?

I've never heard of this, I've heard of opening up the same year cars but never 3 years apart

Theoretically, yes. All it takes is for said vehicles to carry the same unlock/lock codes (uncommon but not unheard of)

Thank you! That helps a ton. I had one more question though. I also had this happen just last week: I confused another person's car with my own but the weird thing was that I could cut the car on but not lock it. Then the guy came out, laughed it off, but then i couldn't unlock it either

3 codes....1 to lock, 1 to unlock, 1 to start. Your car and that one shared the same start code but have different lock and unlock codes

Well that also makes sense, but I was also able to open the trunk with the automatic trunk switch

Ok so I guess there's 4 codes, I forgot about the trunk code, my fob isn't that fancy....just lock and unlock on mine, lol

So I'd assume it's just a crazy coincidence? Also, I don't think I'd call it fancy, my cars pretty old and beat up. It's not even really technological its just a pop up lol

Fancier and newer than mine, it's a 97

I forgot two things. One is for my original, i forgot that they could also start each other's cars, like key in ingnition. Is this possible even with a 3 year difference? And two, on my other question, I forgot to add that it didn't work when I tried to unlock it just a few minutes later when the owner showed up

It's not unheard of but it is unlikely with a factory keyless entry system. GM uses a rolling numbers system for their keyless entry. Each time you use the fob the frequency is a little different. The vehicle knows what frequency to expect next to unlock or lock the vehicle. If that frequency is not transmitted the vehicle won't respond. There are, I believe, 250 frequencies in the sequence. Aftermarket keyless entry systems are not that sophisticated. Hope that helps! Jim

Oh so you're saying the,frequency could be say, number 155, and mine unlocked with frequency 155, but the lock was a different frequency? And then the frequencies changed again so i couldn't unlock it? How many cars work like this? I don't know if mine does so this could actually be the answer

Yes, that's correct. Your fob and his vehicle were, by coincidence, in sync the first time. But the second time his vehicle was expecting a certain frequency but your fob transmitted a different frequency than what was expected by his vehicle. GM used this system for several years across many models. You will see different styles of fobs for different GM divisions and models to prevent what happened with you. But the system isn't foolproof. When I bought my 2000 Grand Prix it didn't have any fobs for the keyless entry system. I bought two and synchronized them to the vehicle. The owner's manual for the vehicle warns that if the spare fob is not used for a long time it can fall out of sync with the vehicle and need to be synchronized to the vehicle again. Hope that helps! Jim

So ....basically you're saying that I could grab a random fob and walk up to a stranger's car and that if I keep pressing the button it will eventually work?

But I had a Nissan when this happened, I don't think they fit this criteria

Theoretically you can if it's it uses the same fob as what you have. I'm not familiar with other makes though. Only GM systems. Jim

Ok that makes more sense, what do you think it could be if the Nissan doesn't fit this though?