Alarm system goes off when using the key to unlock the door to get in.

thats normal gm programmed their alarm system that way

Door Key Switch
The BCM monitors the door key switches in order to disarm the CTD system. When the lock cylinder turns in order to unlock the door, the switch grounds the disarm input to the BCM.
The key lock input to the BCM is probably missing , BCM doesn't see it . So it think's your breaking into the vehicle. Did you try the passenger door to see if it will disable the alarm .
The BCM - body control module ! Electronic -computer !
--------------------------------------------------------------------------------
Content Theft Deterrent (CTD) Does Not Disarm with Key Lock

The factory service repair manual has a 23 step diagnostic procedure . An you would need a factory scan tool to find the correct fix.
Turn ON the ignition with the engine OFF.
With a scan tool, observe the door key switch parameter in the Body Control Module (BCM) security data list.
Does the scan tool display INACTIVE?

Locking the Vehicle Without Arming the System
Use one of the following procedures in order to lock the vehicle without arming the system:
• Procedure A -- Lock the vehicle using the manual door lock knobs. Close all the doors.
• Procedure B -- Close all the doors. Use the key or the power door lock switch in order to lock the door. The doors must be closed prior to locking the doors for this procedure.
Disarming the System
In the arm initiated mode, the following conditions are true:
• The security telltale is ON.
• The doors are open.
In order to disarm a system in the arm initiated mode, perform one of the following procedures:
• Press the power door lock switch to the UNLOCK position.
• Press the door unlock button on the key fob.
In order to disarm a system in the arm delay or the armed mode, perform one of the following procedures:
• Use the key in order to unlock one of the doors.
• Press the door unlock button on the key fob.
Deactivating the Alarm
In the alarm mode, the following conditions are true:
• The horns sound intermittently.
• The headlights and the park lamps are flashing.
In order to deactivate a system in the alarm mode, perform one of the following procedures:
• Use the key in order to unlock one of the doors.
• Press the door unlock button on the key fob.
• If the vehicle control module (VCM)/powertrain control module (PCM) receives a valid Passlock™ ignition key rotation.

Aftermarket alarms have to be configured to bypass the factory alarm system when using it.
I don't mean you have to permanently delete your factory alarm. What I am saying is, when you use your autopage key fob to unlock your doors, it must also send a signal to the disarm wire of your factory system simultaneously. If not, your alarm will go off just like you are experiencing.

Disarming an Armed System/Silencing an Alarm
If system arming has been requested by the keyless entry transmitter, it must be disarmed.
Important: Using the power door unlock switch or manually unlocking the doors does not disable the CTD armed mode. Also, disconnecting the battery or pulling fuses does not disable the armed mode, since the BCM stores the CTD mode status in memory.
?€¢
To disarm the CTD system in arm pending mode, SECURITY indicator flashing and doors open, perform 1 of the following:

-
Press the UNLOCK button on the keyless entry transmitter.

-
Insert a valid key into the ignition and start the vehicle.

?€¢
To disarm the CTD system in the armed mode:

-
Press the UNLOCK button on the keyless entry transmitter.

-
Insert a valid key into the ignition and start the vehicle.

?€¢
To disarm the CTD system when activated, alarming mode.

-
Press the UNLOCK button on the keyless entry transmitter.

-
Insert a valid key into the ignition and start the vehicle.

You will needs to think of it this way. Once you set your alarm it is looking for the corresponding signal to disable itself. That comes from the fob. If you don't use the fob and just use the key, the alarm system is doing its job and alerting you since it has not received the disable command from the fob. Either lock the door with the button when you exit the car if you want to use the key or use the alarm fob. This will also happen if you use the car manufacturers fob to unlock the car if you have locked it with the alarm manufacturers fob.

Hope that helps - I have hidden all of my original car fobs to help alleviate this problem!

Are you using the the keychain to lock unlock the vehicle? A low battery in the keychain will send wacky codes to your vehicle alarm system and will not set properly. Try using the key in the door to lock unlock vehicle. IF the alrm does not go off when using the key in the door, then you probably have to change the battery in the key chain. Best guess without being there to look at vheicle.

put your key in the door and turn it firmly to the unlock postion... I believe it is to the front of the car... then back to center...
The factory alarm can be armed /disarmed by the key in the door.

K

Do you have a key fob? Unlock the car with that and you should be OK. My sons Elantra is the same way, you can only get in with the fob. I guess the car thinks it's being stolen otherwise. If you don't have a fob, I'm no help

If your car has an alarm with a separate remote, it is a separate system and it is probably self-arming. When you lock the doors with the key central lock, the alarm gets armed by the RAV4 being OFF and the door locking action. When you unlock the doors with the key, the alarm is still armed because the key is not comunicating with the alarm just the cars factory keyless system.