Most vehicles come with a factory keyless entry system which includes two factory keyless entry remotes. Most of the time, the factory system is only for keyless entry and does not include alarm or remote start.
There is something called an aftermarket add-on which will add selected features to your factory keyless entry system and it will function using your factory keyless remote. The most common aftermarket add-on systems are for alarm or remote start. There are also window roll-down and trunk pop capabilities on some add-on systems.
The following video is a demonstration from one alarm shop of an add-on alarm system they put into a vehicle. Note that not all add-on alarm systems work exaclty this way. The system they installed does function this way but there are other systems made by many different manufacturers including DEI, Omega, and Crimestopper, among others.
Watch this video to get an idea how the systems function.
There are many types of systems that DEI makes. They make systems under the following brand names: Automate, Avital, Clifford, Designtech, Hornet, Python, Rattler, Valet, and more…
The systems can perform any combination of the following functions: keyless entry, alarm, remote start, and more…
This video shows a remote start, keyless entry, alarm system.
Customer question we recently received via email:
We have a 1997 Ford Explorer with a keypad on the door and remote keyless 
locks. Apparently, the previous owner installed an aftermarket alarm system because when we went to a locksmith to get a replacement fob, he told us he couldn’t program it because it was an aftermarket installation. The fob that we have is falling apart but it is made by KARR. We searched your site and found what looks like the same fob; yours says it is FCC ID ELVAT5H. You apparently don’t ship the KARR part; it looks like you ship a clone as a replacement. We already tried to order a replacement over the Internet and wound up with a fob that can only be programmed with the factory-installed alarm and does not work with the one we have. We can program the aftermarket fob using the factory 5-digit code but the replacement we got doesn’t program. If we order the replacement fob through you will we get the clone and will it be programmable with an aftermarket alarm using the original factory code? Thank you.
Our answer:
I know you think you reprogrammed you KARR remote with the factory programming procedure but it is impossible. Your remote never ceased to be programmed so it seemed to continue to work which you must have interpreted as meaning it was reprogrammed. I believe what happened is that during the factory programming procedure when it says to press the button on the remote so it will be learned, you pressed the button on the KARR remote, the door locks either locked or unlocked (similar to the way the procedure indicates will happen to confirm programming was successful) and you interpreted that to mean it was programmed.
The KARR clone replacement remote we sell is the right remote for you to order. However, you will use the KARR programming instructions to perform the programming. A KARR remote can not be programmed with the programming instructions for the factory keyless entry system because the KARR system has no way to detect that the factory procedure is being performed. The KARR system is designed to detect only the KARR procedure being performed.
How this may apply to you:
Perhaps your old remote is this same KARR 3 button remote and you need an additional remote or you need to replace your old remote because it is not working. You can order a replacement through us and it will come with easy programming instructions. Free phone tech support over the phone is available for those who need it.
It is 6am and you need to go to work. You go to open your car and the alarm starts blaring. You lost your remote or your remote does not work all the time. You are waking your neighbors and it is embarrassing. How many of you have been there? I have not myself, but I have heard this story at least a dozen times from customers.
I hope that the advice below will help you out so you can start driving to work. Nevertheless, before I forget: ORDER A REMOTE so you don’t have to keep going through this.
On a related note, yesterday a customer with a factory alarm had a similar situation and even though he had a factory keyles entry alarm remote, he insisted he wants to open the door with the key. I tried to explain to him that if he locks the door with the remote he has to unlock it with the remote – not the key. Well, 20 minutes into the call I’m not sure if he really understands and he confirmed it by entering the car with the key and setting off the alarm while I’m on the phone. Don’t be that guy. Use your remote if you have it. I won’t even tell you him dumb reason for using the key instead of the keyfob.
Let me start by saying there is no one way to turn off the alarm. What I will do is take you through my process if I were in the situation. First, we need to know what we’re dealing with. Is it a factory or aftermarket alarm?
Factory means it is the alarm system that was installed at the time the vehicle was built. Aftermarket means it was installed in a shop after the vehicle was first bought.
Factory Alarm
If your factory alarm is blaring because you locked the car with the remote (and it armed the system or if the system arms itself) and then you open the door with the key instead of the remote, then in most cases starting the car with the key will stop the alarm from blaring.
If not, close the door and turn the key in the driver’s side door lock twice - like this: LOCK UNLOCK, LOCK UNLOCK.
If that doesn’t work and you can still use the radio, jot down all your
programmed stations because what I am about to suggest will make you lose them. Disconnect your battery for 5 minutes.
Disconnecting the battery for 5 minutes will usually (maybe 7 times out of 10) reset the alarm and resolve the problem. Some cars have a radio security feature called radio lock. If your radio 
gets locked you can call your local dealer parts department, give your VIN and they will give you the radio unlock code.
If not, and if this is an older car from the 90s you may be able to disconnect the system. I won’t give you advice on that because I’m afraid you’ll screw up your car and blame me. See an alarm shop, qualified mechanic or preferably an automotive electrician. In most cars from the 2000s to now, the factory alarm is
integrated into the car’s computer (sometimes called PCM, BCM, or ECM) and trust me you do not want anyone messing with it. You can see the dealer for option programming. This means they hook up a proprietary scan tool to the car and communicate with the car’s computer to tell it how to behave - in this case to disable the alarm. Not all vehicles have this option available.
In the end if none of this works for you then the dealer can replace the system for you – probably at an outrageous cost.
Aftermarket Alarm
There are so many different brands and models of aftermarket alarms that this advice may not apply to your system. However, I will “guesstimate” that it applies to 90% of systems out there.
The first thing to try is to put the system into valet mode. Valet mode is the state of the system you want to put the car in when you give your car to valet parking. That way you just give them a valet key and no remote (so there is nothing expensive for them to lose.)
As I said, there are many different systems and so there are many ways to enter valet mode. The most common is described below:
1. Open the driver door.
2. Put the key in ignition and turn to ON. (ON is where the dash has power but you are not cranking the engine yet.)
3. Press the valet button or switch one time
Variations to try:
• Don’t open the driver door in step
• Turn engine ON instead of just the dash.
For those who don’t know what I’m talking about when I say valet button or switch, check out these pictures:
With the brand and model name of your system, you can search online for the owner’s manual of the system. It will say how to enter and exit valet mode with exact instructions for your system. The brand and model name of the system are located on the receiver. Maybe only the brand will be on the remote – if anything. The FCC ID or part number on the back of the remote will narrow down the search to a few systems but it isn’t enough to isolate one particular system. Most remotes work on a bunch of different systems. The receiver is located under the dash. Stick your head where your feet go and look up.
Even though the proper installation of the system includes the valet switch or button, not every installer uses best practices when installing the system. If you can’t find the valet switch, see the following article: TROUBLESHOOTING WHEN YOU CAN’T FIND THE VALET SWITCH.
If that doesn’t work then we move on to try to reset the system. If you can still use the radio, jot down all your programmed stations because what I am about to suggest will make you lose them. Disconnect your battery for 30 minutes. Normally 1 to 5 minutes will suffice but many alarm systems have a battery backup to prevent car thieves from disconnecting the battery.
Disconnecting the battery will usually reset the alarm and resolve the problem. Some cars have a radio security feature called radio lock. If your radio gets locked, you can call your local dealer parts department, give your VIN and they will give you the radio unlock code.
Let’s say that doesn’t work. My next question is whether your alarm is just
blaring a siren but you can still drive, or is there a starter cutoff associated with the alarm as well.
If you are not dealing with a starter cutoff and your alarm has its own siren, then you can just snip the wire about an inch before the siren. If your alarm uses the car’s horn then do not tamper with that – it is probably illegal in most states to disable the horn.
If you do have a starter disable with the alarm, then cutting the siren will not do any good – unless you’re so sick of hearing it you’ll feel immense relief knowing you’ll never hear it again. You still won’t be able to start the engine and drive.
Aftermarket alarms are not integrated into the car’s computer so there is no harm in simply disconnecting it. They have wires plugged into the receiver (the brain of the system.) Simply unplugging them will do the trick. The receiver is located under the dashboard – usually on the driver’s side. Put your head near the pedals and look up. If you don’t see it, try the passenger side. The receiver won’t be under the hood or in the trunk.
The receiver (a.k.a. brain or control module) is a plastic box with wires coming out of it. If will usually have the brand and model name on it. Therefore, if your remote says Viper and the box says Viper, you know your looking at the right box. It may be approximately 3” x 5”x 1”. Sizes vary greatly but it will definitely be significantly smaller than a box of tissues.
If you find a smaller box – maybe the size of a pack of cigarettes or smaller – it is not the receiver. That is probably a shock sensor or some other accessory module associated with the system. However, follow the wires from that module to the receiver of the system. If you know where your valet switch is, or you see the LED light from the alarm, then follow the wire from that to the receiver.
Some installers put the system so deep into the dash you can’t find it without taking off the lower dashboard cover or kick panel. I hate when they do that. If that is the case for you then my suggestion is not to take apart the dash and instead go to an alarm shop, automotive electrical shop, or very qualified mechanic.
There is one more situation that can cause the alarm to go nuts. I call it "Everpress." This is where a defect with the remote causes it to constantly send out a signal. It isn't very common but I've seen it few times. When it first starts, it is not possible to detect unless you have a keyless entry tester. But after about 24 hours you can tell because the battery in the remote is dead. It is caused by a faulty button or excess moisture making contact for the button. If Everpress is causing your alarm to go nuts then just take the battery out of your remote and order a new one. If you just changed the battery of your remote and are having everpress for the first time, then you probably closed the remote poorly and one of the buttons is in the pressed position.
We find frequently customers will order the wrong remote for their car. Sometimes they order a remote because they like how it looks. Other times they order a factory remote when their old remote is an aftermarket remote that looks totally different.
This morning I did an exchange for a customer. Her old remote 
was a Viper 474V (picture to the left.) The Viper 474V is an aftermarket remote. She went to the website and looked up the year and model of her vehicle (which was a 2004 Toyota Camry.) Doing that brought up the factory remote (picture to the right.) Even though the factory remote looked nothing like the remote in her hand she ordered it because she liked how it looked.
If she looked closely her old remote has FCC ID: EZSDEI474V and the remote she was ordering has FCC ID GQ43VT14T. These FCC ID's are not compatible. It is very rare for different FCC ID's to be compatible. Sometimes remotes with the same FCC ID are not compatible with one another.
Let's pretend she lost her old remote but still remembered what it looked like. When she looks up the factory remote she should recognize that her old remote didn't look like that. What should she do?
Then she would look under her driver side dashboard for the receiver of the keyless entry system. It will be a plastic box with wires coming out of it. If there is a valet button/switch or LED light on the dash or consol, the wires from the button/switch or LED will go straight to the receiver she should look for. Once she finds the receiver the can read the Brand and Model Name of the system and use that on our website to lookup which remote she should choose.
Many aftermarket system programming procedures call for the use of the programming button or valet switch or button.
Below are examples of the button or switch:
Sometimes when an alarm shop installs an aftermarket system with a valet/bypass switch they don't mount the switch or they don't hook it up completely.
What you need to do is look for the keyless entry receiver (brain). It is usually located under the dash on the driver or passenger side. It is a plastic box with wires coming out of it.
It will have plugs where the wires go in it. It may have two to four plugs. The largest plug will definitely have wires plugged in. Then there will be smaller ones. One of the smaller ones will have blue plastic surrounding the plug. That is where the valet switch plugs in.
If there is something plugged in then follow the wire as this leads to where the switch/button is located. If there is nothing plugged in then take a metal paper clip and touch it to both metal terminals inside the blue plastic plug. This will make the system think you are pressing the valet switch/button.
Factory remotes work on factory systems, which are the original systems that are installed in the vehicle when it is built at the factory.
Aftermarket remotes work on aftermarket systems. Aftermarket systems get put in a car after the car is no longer brand new. Alarm shops, Best Buy, and dealerships typically are the ones that install aftermarket systems in cars. There are many different aftermarket brands that are common.
The most popular aftermarket remotes are made by DEI. DEI's most popular brand name is Viper. Most people have heard of Viper because of the commercials they had in the late 1990s (the car would yell "this car is protected by Viper - stand back!")
Factory remotes and aftermarket remotes are almost never compatible with each other. Make sure you order the correct type of remote or it will not work on your vehicle.
If you have a remote that works or worked on your vehicle you can use the FCC ID and/or part number to search for the correct replacement. They will usually be located on the back of the remote (either on a sticker or molded onto the case.)
To determine if your vehicle was built with factory keyless entry, locate your VIN number (on a plate at the lower drivers side where the dash meets the windshield and on the production sticker on the driver door frame) and call your local dealer parts department. Tell them your VIN number and ask if your vehicle is equipped with factory keyless entry.
To determine if your vehicle is equipped with an aftermarket system look for telltale signs such as a valet switch or button, or an LED mounted to the dash that looks like it was put in after the factory.
Some aftermarket systems call for using the valet switch during the programming procedure. Use this troubleshooting procedure to help you either find the valet switch or fool the system into thinking you are using one.