I have a 2009 Tahoe SSV that was functioning completely normal. While working to enable the rear tail light flashers blue/yellow wire some of the BCM pins were shorted to ground momentarily during testing and now the vehicle will not turn over and has the security lock light on. Attempts to reprogram the key using the 30 min procedure were unsuccessful due to the security light staying on solid and never turning off during the reset procedure. No ODB2 codes show and the key is reported to be showing up in the BCM. The vehicle was towed to a local dealer to reprogram a used bcm or the original bcm without any changes in the security lock. Does anyone have any suggestions? The dealer is 3 weeks out from being able to look more in-depth at the vehicle so any thoughts would be helpful.

 

Most likely a poor connection right at the battery. The minute you put in a demand for power,the connection says , not today.

Start with removing the Black colored negative cable from the battery and with something like a wirebrush, clean the cable connection and the terminal at the battery.
Leaving the negative cable still off, do the same cleaning procedure to the Red, positive cable end and battery terminal. If you look carefully you will probably see some white corrosion at one or both of those connections.
When you disconnect the battery from the vehicle, you could get some unusual performance that goes away as you reestablish your driving habits in the vehicle computer by just normal driving.
Let us know how you make out,thanks.