It could be many things.
When the engine crank but won't start
Retrieve PCM faulty code if any.
Engine need 3 things (Fuel, Air, Fire (spark)
1- Fuel = fuel pump working during the problem you can hear a sound at the fuel tank cap (remove)
All Fuel Injectors working.(Power and the spray).
2- Air = MAF defect (Mass Air Flow) no code will be set
When the engine is running with a screwdriver lightly hit the MAF the engine will stall if it's the problem.
air filter restrictions
3- Fire= Is there spark at all spark plugs wire?
Find out the ground of power windows it could be the same as fuel pump or ignition system (Ground corrosion, high resistor)
and many more.
See good technicians to fix your car..
This is a very common problem on GM vehicles. The security system is known to fail. Basically when you insert your key, the system checks for certain OHMS resistance. If the system cannot get the correct signal from the key, it assumes the key is incorrect and goes into SECURITY lockout mode. (prevents hotwiring) This has been happening with GM;s for a very long time. If the light comes on, but you can still start it, thank the lord. Failure is coming soon. There are ways to bypass this now. Read through this page for info, solutions as well.
The anti-theft system has nothing to do with spark . When it won't start check for B+ voltage at the ignition module . pin P a pink wire . Check pin K for a good ground . Check the 18X & 3X crank sensor signals to the PCM . It's good you have a snap on scan tool an can check sensor data , but to check cam an crank signal's you really need a scope ! Does your snap on tool have a lab scope ( oscilloscope ) Do you know what this is ? How to test crank sensor on GM 3800 engine 3x and 18x signals
Do you have access to wiring diagrams ? Check electrical distribution in an out of the ignition switch .Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info Year , make , model and engine size . Under system click on electrical distribution , then under subsystem click on power distribution . Click the search button , then the blue link ! I wouldn't think the ignition switch being the problem but you never know without testing ! Do you know how to do automotive electrical testing with a DVOM - digital volt ohm meter ? Using a wiring diagram to pin point areas for testing ? Electric Testing Techniques You Need to Know
TSB'S that GM may have on this car. For what ?
How did you test the A/C system ? Hook up gauge manifold , test A/C pressures ? Manual or automatic climate control ? The blower motor only working on high means the blower motor resistor is bad ! Did you hook up a scan tool an check high an low pressure switchs inputs to the PCM - engine computer . Does the A/C compressor clutch engage ? turning on the compressor ? Moving the mode switch does nothing . Doesn't move from floor to vent to defrost ? Probably the mode door actuator ! Don't think the HVAC control panel is bad . Just a few little things . Pushing the A/C button on the control panel just send a electrical signal to the PCM , the PCM will energize the A/C clutch relay , turning on the compressor .
Daytime headlight issue ? No , no sensor behind the front bumper . No Daytime time head lamp issue , doesn't turn on the instrument panel light's . This is more then likely a remote dimmer module problem .
Interior Lights Dimming Circuit Description (Pontiac)
When the park lights are on, battery positive voltage (B+) is applied via CKT 32 (YEL) to the remote dimmer module. The interior dimming switch in the lamp dimmer switch is a variable resistor which applies the dimming input via CKT 44 (DK GRN) to the remote dimmer module. The potentiometer in the lamp dimmer switch cannot provide enough current in order to operate the incandescent lights. The remote dimmer module amplifies the current, applying a variable voltage to the incandescent lights. As the amount of current increases, the lamps become brighter. As the amount of current decreases, the lamps become dimmer.
The radio, heater and A/C control assembly, instrument cluster, and passenger climate control each has a vacuum fluorescent (VF) display. When each module receives an input that the ignition switch is turned to the RUN position, each module activates the VF display at the full intensity. When the park lights are on, the radio receives the dimming level from an input on CKT 8 (GRY). The radio then relays this information to any other modules with VF displays. All modules with VF displays then adjust the dimming level of their VF display in order to match the level of the incandescent lamps.
Is there an illuminated check engine light on the dash? That sounds like a failing TPS (throttle position sensor). Unless you have low fuel pressure! When (if ever) have you replaced the fuel pump and/or fuel filter? Are you running the correct type of fuel in the engine? If you have slow or sticky fuel injectors, a can of Seafoam might help!