How is the battery ? Do the headlamps shine bright ? Did you check the crank relay an the crank fuse 40amp ? one of the big one's ,maxi fuse . Under hood fuse / relay box . Check to see if voltage is coming through the transaxle range switch.
When the ignition switch is on, battery voltage is applied to one side of the crank relay in the underhood accessory wiring junction block through circuit 3, the PCM-BCM Fuse in the fuse block, and circuit 439. When the ignition switch is turned to START, voltage is fed to the powertrain control module connector C2 terminal 23 through circuit 5, the CRANK SIGNAL Fuse in the fuse block, and circuit 806 through the underhood accessory wiring junction block. Power is always provided from the CRANK MaxiFuse in the underhood accessory wiring junction block to the common side of the crank relay contacts. When the powertrain control module sees the crank signal and determines that conditions are OK for a crank, it supplies ground through circuit 625 to the crank relay. The crank relay now has both power and ground to the relay coil, causing the relay to pull in. When this happens, and the gear selector is in either PARK or NEUTRAL, the power at the relay common contact is passed through circuit 1737, the transaxle range switch and circuit 6 to the S terminal on the starter solenoid.
Passlock Theft Deterrent System
This vehicle is equipped with the Passlock theft deterrent system. This system contains a Passlock sensor. The Passlock sensor is part of the ignition lock cylinder assembly. The Body Control Module (BCM) interfaces with the Passlock sensor.
When turning the ignition switch to the START position with the proper key, the Passlock sensor generates an analog voltage signal, which is sent to the BCM. This analog voltage signal is of a specific value to the vehicle, and varies from vehicle to vehicle. When attempting to start the engine, the BCM compares a preset stored analog voltage value with the signal coming from the sensor. Because both values match, the BCM sends a fuel enable password via the Class II Serial Data Line to the Powertrain Control Module (PCM). As a result, the PCM enables the crank relay, and allows fuel delivery to the engine.
When attempting to start the engine by means other than using the proper key in the ignition switch, the Passlock sensor sends a analog voltage signal of a different value. The BCM compares the preset stored analog voltage value with the signal coming from the sensor. Because both values do not match, the BCM sends a fuel disable password via the Class II Serial Data Line to the Powertrain Control Module (PCM). As a result, the PCM disables the crank relay, and does not allow fuel delivery to the engine.
For more information regarding the Passlock theft deterrent system, refer to Theft Deterrent in Body and Accessories
This starting system is computer controlled , if you are not familiar with this I suggest you take a GM dealership or an ASE certified repair shop .