Does nothing? As in doesn't light at all?
Turn the key on but do not crank. Does the theft light come on at all? Does it go out after a 3 second prove out?
I have got to tell you that a sudden loss of fuel injector pulse is exactly how the PATS system disables the motor.
Inspect the main PCM electrical connector for evidence of water damage. Check the PCM for an external performance chip. The contacts on the external chips are bad about rusting. This leads to poor connections and all sorts of strange behaivor.
Yes I could see water damage causing all sorts of issues.
2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.