I hope that you purchased a KNOWN working "used" TCM. The nightmare that is the GM supply chain has put a lot of bad used tcm's into the hands of unscrupulous scammers. The TCM in this truck is the most vulnerable component in the truck, mounted on the hottest spot of the engine compartment with no airflow. With the supplier shelves now completely empty, this appears to becoming a major industry event, leaving perhaps thousands of these trucks stuck in driveways, as GM works to find a new supplier. This could take months, or longer.