sorry to keep you waiting
1-is there a red security light flashing or steady on dash while trying to crank ?
2- You need to have the vehicle scanned by a GM diagnostic scanner or equivalent that can communicate with Anti theft module and retrieve the fault codes in the module memory and based on the fault code numbers, we can look up the Troubleshoot on it & also the scanner be able to, check the key immobilizer, in case the system lost the key synchronization with the anti theft module,& also check several components of the system , like the antenna ,the receiver module, door switches etc...
3- do you have one or 2 keys ,and have you tried to start with the other one .
4- has this problem happened before or first time or it is been intermittent issue with the vehicle ?
You can try this procedure below ,sometimes it will reset the module, but not all the time, even if it cranked up you still the system tested to see what caused it .
Master Reset Procedure
1-Disconnect battery ( Both Cables ,The Negative & The Positive Cable )
2-Touch Cables together and hold 60 secs and let go
3-Hold Brake pedal down 10 secs
4-Wait 15 minutes and then Reconnect Battery
5-Close all the doors ,hood & trunk .
6-lock the car with key from driver door ( IF your car is Equipped with a bladeless key , then just locked with the keyFob)
7- Unlock car & Start your vehicle
please let me know
ASE Certified Technician