Factory Keypad Code

The code is usually on the back lift gate on one of the hinges or the lift support it is a five digit number usually on a little white sticker about a half inch long, or it;s imprinted on the hinge If the sticker is not there somebody took it off, then you have to go to the dealer and that can cost.
Here is the location with full instructions:
The module is fastened to the top of the firewall directly behind the fuse box. It can be reached easily when you lie on your back in the driver floor area with your head close to the brake pedal. Just look up and you'll see it is clearly marked and the sticker also displays the factory-set access code for your truck.
Once you locate the module Make a note of the 5-digit access code on it.
Once you find the code, here is how to program it:

Now that you have the codes follow these steps to operate it completely. Remember from the driver’s door, all operations must start with the 5 digit code first then follow it with the other options.
When pressing the controls on the keyless entry keypad, press the middle of the buttons to ensure a good activation.

IMPORTANT: Every step outlined in every procedure below must be done within five (5) seconds of the previous step.

REMEMBER THIS: If you try the factory code first and it doesn’t work try to reset the keypad back to the factory code. Your personal code does not replace the factory-set code. So no matter what you can erase anyone’s code back to the factory OEM setting. You can use either code to unlock your vehicle. Each time you set a new personal code the module will erase the previous one in favor of the new code.

Deprogramming (erasing) your own or pre-set personal code and leaving only the factory-set
1. Enter the factory-set code. (5 digit) from the sticker on the RAP module.
2. Press the 1/2 control.
3. Press the 7/8 and 9/0 controls at the same time.
The system will now only respond to the factory-set code.

Unlocking the driver's door (also disarms the perimeter alarm system)
1. Enter either the factory-set code or your new personal code. The interior lights will illuminate as soon as the first valid digit is pressed.

Unlocking all doors
1. Unlock the driver's door (5 digit code) then press the 3/4 control.

Locking the doors (also arms the perimeter alarm system)
1. Press 7/8 and 9/0 controls at the same time. The 5-digit code does not have to be entered.

Deactivating/Activating Auto lock
1. Enter the five (5) digit code.
2. Press and release the 3/4 control while holding the 7/8 control, then release 7/8.

Programming your own personal entry code
1. Enter the factory-set code (keypad will illuminate when first digit is pressed).
2. Press the 1/2 control.
3. Enter your personal 5-digit code.