How do you add R134a to 1998 Pontiac Transport?

To add R134a to a 1998 Pontiac Transport, first ensure the vehicle is turned off and the AC system is off. Locate the low-pressure service port, usually found on the larger diameter AC line, and remove the cap. Attach the R134a refrigerant can to the hose, then connect it to the low-pressure port. Start the vehicle, turn the AC on to max, and slowly release the refrigerant while monitoring the pressure gauge until the desired level is reached.