GMC Troubleshooting Questions? Ask a Mechanic for Answers
Does the starter engage and turn the engine over when the key is turned to Start position?
With the key on, do all of the dash indicators light up? Does a/c fan work, power windows, etc. ?
Did old battery completely die? Was battery, jumper cables, or battery charger inadvertently connected backwards at any point?
Are all of the larger fuses in the underhood fuse panel intact?
Is the security light on or flashing when the key is turned on or to start?
Do you have access to a scan tool? If so, try to communicate with the PCM and BCM and let me know.
They should have a diagnostic scan tool there. Perhaps they could do this for you. If all fuses are good then there is likely a computer glitch or failure. You can try disconnecting the battery for at least 30 seconds to try to reset all modules. After that a scan tool will be necessary to see which modules are communicating and which are not.
The scan tool will tell you if the modules are communicating. Fuses need to be checked visually or with a test light at each fuse.
Connect scan tool to diagnostic port under drivers side of dash. Power up the scan tool and check trouble codes. You will want to check powertrain codes (PCM) and body codes (BCM). Let me know what you find.
Does it check codes at all? If so, what are the code numbers from the scanner?
Sounds like the scanner is very basic, likely only reads powertrain codes and will not talk to the BCM. Has the inspection of all the fuses been completed?
That is what I suspected. Thank you for the update. This sometimes happens when a battery change is done.