Is the security light on in the instrument cluster ? Sounds like anti-theft system problem . The anti-theft does not disable the fuel pump ,turns off the fuel injectors , nor does it disable the starter . So it's probably not the anti-theft system . Your best bet (if you know how ) test power and ground circuits using voltage drop testing , hook up a professional scan tool an do a full system scan of all the modules on the vehicle . Your probably not aware of the sophisticated electronics on that vehicle . BCM - body control module ,Immobilizer Description and Operation
The immobilizer system functions are provided by the body control module (BCM). When an ignition key is inserted into the ignition lock cylinder and the ignition is switched ON, the BCM supplies battery voltage to the theft deterrent exciter module. The transponder embedded in the head of the key is energized by the theft deterrent exciter module which is surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its unique value, which is received by the theft deterrent exciter module. The BCM monitors the theft deterrent exciter module for the transponder value. The BCM then compares this value to a value stored in memory, the learned key code. If the value is correct, the BCM sends the fuel enable password via serial data to the engine control module/powertrain control module (ECM/PCM). If the transponders value is incorrect the BCM will send the fuel disable password to the ECM/PCM via the serial data circuit. The components of the immobilizer system are as follows:
• BCM
• Theft deterrent exciter module
• ECM/PCM
• Ignition key (Transponder)
• Security indicator
Power Mode Description and Operation
Power to many of this vehicle's circuits are controlled by the module that is designated the Power Mode Master (PMM). This vehicle's PMM is the Body Control Module (BCM). The PMM controls which power mode (Run, Accessory, Crank, Retained Accessory Power, or Off) is active.
Serial Data Power Mode
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle, the PMM is the body control module (BCM). The PMM receives 3 discrete ignition switch signals to differentiate which power mode will be sent over the Serial Data circuits. The table below illustrates the state of these inputs in correspondence to the ignition switch position:
Relay Controlled Power Mode
The body control module (BCM) uses the discrete ignition switch inputs ignition 1, ignition 3 and crank to distinguish the correct power mode. Once the BCM has determined the power mode selected by the vehicle operator it will energize the Ignition relay, Run relay and retained accessory power (RAP) relay, depending on which power mode is selected.
Ignition 1 Relay
The relay uses a Hot At All Times B+ power source derived from the underhood electrical center. The ignition 1 relay supplies a power signal to the following circuits when the Run or Crank power mode is selected:
• AC clutch relay
• ABS STG angle sensor
• Antilock brake system (ABS) yaw sensor
• Auxiliary power drop connector
• Crank relay
• Cruse control switch
• Electronic brake control module (EBCM)
• Engine control module (ECM)
• HVAC module
• Ignition control module (ICM)
• Instrument panel cluster (IPC)
• Sensing and diagnostic module (SDM)
• Transmission solenoid circuit
Fail-Safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the power mode master (PMM) fail to send a power mode message. The fail-safe plan covers those modules using exclusively serial data control of power mode as well as those modules with discrete ignition signal inputs.
Serial Data Messages
The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to RUN. In this state the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.
Discrete Ignition Signals
Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid PMM message received on the serial data circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, battery positive voltage, the modules will fail-safe to the RUN power mode. If the discrete ignition input is not active, open or 0 volts, the modules will fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.
WE do not have a clue as to the shape of your vehicle , was it well maintained or is it a POS ? Checking for DTC'S - diagnostic trouble codes in all the modules on the vehicle , no cheap code reader will do this .
do you know what wiring diagrams are ? service repair information ?
https://www.youtube.com/watch?v=efKoWifdcag&t=2180s
https://www.youtube.com/watch?v=j5GaBCPQ4Bc
https://www.youtube.com/watch?v=jxKco2D9i-0&t=804s
If you want to play auto mechanic you better learn what's involved .