2003 Ford Expedition my truck wont start wen I turn key

The PATS uses a specially encoded ignition key. Each encoded ignition key contains a permanently installed electronic device called a transponder. Each transponder contains a unique electronic identification code out of over 18 billion, billion combinations.
The passive anti-theft system (PATS), also known as SecuriLock  uses radio frequency identification technology to deter a driveaway theft. This system is known as SecuriLock  in North America, Safeguard  in the U.K, and PATS in Continental Europe. Passive means that it does not require any activity from the user.
The SecuriLock  System (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. If equipped the remote start system must be removed before investigation of PATS-related, no-start issues.
Each encoded ignition key must be programmed into the vehicle's powertrain electronic control (PCM) before it can be used to start the engine. There are special diagnostic repair procedures described in this section that must be carried out if a new encoded ignition key is necessary.
This system contains a new feature named Unlimited Key Mode. This feature allows a customer to program more than eight keys to the vehicle if they request it. Each vehicle in Unlimited Key Mode is set up with a special Unlimited Transponder Security Key. This allows all the customer vehicles to share the same keys, but no other keys from outside can be used to operate the vehicles. For an individual customer, any randomly selected Security Key is acceptable. Refer to UNLIMITED KEY MODE PROGRAMMING.
The PATS transceiver module communicates with the encoded ignition key. The module is located behind the steering column shroud and contains an antenna connected to a small electronics module. During each vehicle start sequence, the transceiver module reads the encoded ignition key identification code and sends data to the PCM.
The control functions are contained in the PCM. This module carries out all of the PATS functions, such as receiving the identification code from the encoded ignition key and controlling the engine enable. The PCM initiates the key interrogation sequence when the vehicle ignition switch is turned to RUN or START.
All elements of the PATS must be functional before the engine is allowed to start. If any of the components are not working correctly, the vehicle will not start.
The PATS uses a visual theft indicator. The 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 concern, this indicator will either flash rapidly or glow steadily when the ignition switch is turned to RUN or START. The PATS system also flashes the theft indicator every two seconds at ignition OFF to act as a visual deterrent.
The following will activate the PATS and will disable the vehicle from starting:
incorrectly encoded ignition key
damaged encoded ignition key
unprogrammed key
non-encoded key (key has no electronics)
damaged wiring
damaged transceiver
damaged PCM
Inspection and Verification
Verify the customer concern by operating the system.
Visually inspect for obvious signs of mechanical and electrical damage.
If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
If the diagnostic tool does not power up, refer to the diagnostic tool manual.
Carry out the DATA LINK DIAGNOSTICS test. If the diagnostic tool responds with:
CKT914, CKT915 or CKT70 = ALL ECUS NO RESP/NOT EQUIP, refer to MODULE COMMUNICATIONS NETWORK.
NO RESP/NOT EQUIP for PCM, refer to REMOVAL & INSTALLATION article.
SYSTEM PASSED, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out self-test diagnostic for the PCM.
If the DTCs retrieved are related to the concern, go to the (PCM) Diagnostic Trouble Code (DTC) Index to continue diagnostics.
If not DTCs related to the concern are retrieved, proceed to the SYMPTOM CHART.