Follow these free keyless entry remote key fob programming instructions for 1999 Chevrolet Astro.
1. Locate the Data Link Port. It is located under dash drivers side. Be sure you know which pins are 8 and 4.
(Notice port is wider on top row)
2. Make sure there are metal contact pins in terminals 8 and 4. Connect 8 to 4 with a suitable jumper wire leave the jumper wire connected throughout the programming procedure). Make sure you know which terminals are 8 and 4. The vehicle will respond by locking and unlocking the doors to signify entering of programming mode.
3. Press and hold both the LOCK and UNLOCK buttons together on the first transmitter to be programmed. After about 15 seconds, the vehicle will respond by locking and unlocking the doors. Release the buttons on the transmitter.
4. Within one minute, repeat the previous step on the remaining transmitters to be programmed.
5. Remove jumper wire applied to the OBDII Port.