No-Start After Shifting Gears in Accessory Mode - Anti-Theft System Reset

Car would not start after shifting out of park while the key was in the accessory position. The factory anti-theft system interpreted the unusual gear shift sequence as a theft attempt and locked out the starter circuit.

The factory anti-theft system on the MKIII Supra misinterpreted shifting out of park with the key in accessory mode as a theft attempt, activating the starter-kill relay and preventing the car from starting. The aging anti-theft system (30+ years old) can become erratic in its detection logic.

Low confidence — Original poster confirmed this resolved the issue