2002 ford explorer xlt 4x4... Vehicle won't start

Disconnect the battery terminals and wait 5minutes reconnect them when the alarm sounds use your keyfob to turn it off you should be out of theft mode and functioning properly

My mechanic disconnected the security section because my key I use to start the car had the security spot on the key was loose and would not work in the ignition It was going to cost a lot for a new set of keys so he took the security section out for a lot less. As he said an older car does not need security.

There is no PATS override button. PATS is Passive Anti-Theft System. It is a transponder chip in the key, and a transceiver ring around the ignition lock cylinder. The Ring looks for the correct chip in a key in order to allow the vehicle to start. A bypass or override button in the vehicle completely advantage of having the chip system and would render is useless in entirety.

Is the red light on the top center of the dash pad flashing fast when trying to start ? The engine doesn't turn over ?
Anti-theft system problem !
PATS uses a visual theft indicator. This indicator will prove out for three seconds when the ignition switch is turned to RUN or START under normal operation. If there is a PATS problem, this indicator will either flash rapidly or glow steadily when the ignition switch is turned to RUN or START. PATS also "blips" the theft indicator every two seconds at ignition OFF to act as a visual theft deterrent.
PATS differs from the perimeter anti-theft system in that PATS enables and disables the engine from starting. If equipped, the perimeter anti-theft system protects the perimeter of the vehicle (doors, hood and trunk) and sounds an alarm.
The PATS is not compatible with aftermarket remote start systems, which allow the vehicle to be started from outside the vehicle. These systems may reduce the vehicle security level, and also may cause no-start issues. Remote start systems must be removed before investigation of PATS-related No Start issues.

Anti theft will stop it from starting. Try locking and unlocking the drivers door with the key to reset .

Call the dealer

Do you have a question ?
Have you tried another key ?

You should have lights - so check the battery cables and fuseable links first.
Is the battery fully charged ?

if anti theft module not communication with scanner or diagnostic hook up then your vehicle will probably not start till thats corrected and clicking sounds like relay from security system opening up and shutting down power for starting system