The airbag light will go out after the fault is corrected. Usually, AutoZone only does OBDII codes.
2006 and earlier Rangers use a Light Fault Code for the Restraints System - no code reader required. Just turn on the ignition and immediately count the 2-digit code pattern flashed out by the airbag light. Post it here and we will interpret.
2003 FX4 Level II, Supercharged 5.0L V8, Headers, Duals
BW4406 manual transfer case, Aussie Locker, Torsen L/S, 4.10's
Bilstein 7100 rezzies, Cadillac/Mustang rear discs, Duff traction bars
Keypad Entry, Lock LEDs, ABS switch, sway bar discos
Heated seats, Explorer EATC, Trip Computer and consoles
2003 XLT 2.3L M5OD-R1 reg cab beater, 2011 Taurus SEL, 2016 C-MAX Energi Plug-in Hybrid