Transmission Control Module (TCM)
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The TCM adjusts shift patterns to minimize shift during PTO operation. The TCM also provides transmission gear states and temperature conditions to the PTOM via serial data messages.