Over time, the factory TCM (Transmission Control Module) that controls the Allison transmission behind your Duramax engine is known to fail. Symptoms of this type of failure include losing the "PRNDL" display on your dash, check engine lights, and even limp mode. This is a direct replacement, pre-programmed TCM from the electronics experts at Synapse Auto that plugs right in place of your stock unit for a simple repair. If you're experiencing any of these issues, feel confident in replacing your TCM with this unit from Synapse.