How do you program the built in garage door opener a 1998 Mitsubishi Diamante?

The 1998 Mitsubishi Diamante doesn't have a built-in garage door opener in the same way some modern cars do. It doesn't have a dedicated button or receiver within the vehicle's system. To open your garage door from your Diamante, you'd need to use a separate, aftermarket universal garage door opener transmitter. These are small devices that you'd plug into your car's cigarette lighter or use a clip-on mount. You then program the transmitter to work with your garage door opener's receiver.

The programming process varies depending on the brand of your universal garage door opener transmitter. However, the general steps usually involve:

1. Learning Mode: Putting your garage door opener into "learning mode." This is typically done by pressing and holding a button on the garage door opener's motor unit itself. The instructions for this will be in your garage door opener's manual. (Often it involves pressing and holding a learn button).

2. Transmitter Programming: Pressing and holding a button on the universal garage door opener transmitter while it is plugged into your car's cigarette lighter, or following the specific instructions for the transmitter. This transmits the code to the garage door opener motor unit.

3. Confirmation: Your garage door should open and close, confirming that it has learned the new code from your universal transmitter. If it doesn't work, try repeating the process.

In short: you don't program anything *in* the car; you program a separate device to work *with* your car and your garage door opener. You'll need to purchase a universal garage door opener transmitter separately. Look for one at an auto parts store or online. Make sure to check the compatibility of the transmitter with your specific garage door opener model.