Gen IV engine controller identification
The E40 controller was used on the 2005-06 LS2 engines exclusively. It is designed for the 24X crank reluctor (the only Gen IV exception) and the 1X camshaft reluctor mounted under the front timing cover. It is identified by its three connectors, a 56 pin blue and gray and a 73 pin black. Not to be confused with the E67 ecm which has two 73 pin connectors (black and gray). The distinctly larger pins is the grounds for the ecm.
The E38 controller is used on the 2007 and later truck line equipped with the 4.8, 5.3, 6.0 and 6.2L V8 engines. It is noticeable different in that it has two connectors, 73 pin black, and a 80 pin gray.
The E67 controller is used on the V6 and V8 car line starting in 2006. Next to the E38, it will be by far the most common Gen IV you will see. It is noted by three connectors which is 56 pin blue, and two 73 pin black and gray connectors.
It must be noted that the controllers will only fit the specific engine/transmission it was designed for. The different slotted dividers on each connector makes it virtually impossible to make a wrong connection.
A major difference on the Gen IV engines, is the use of a separate controller for the automatic transmissions. Shown here is the T42 controller, used only with the 4 speed automatics (4L60, 65, 70E). It is a 49 pin connector, the large pin is the ground. The 6 speed automatics use the T43 controller which is located in the transmission pan. These are known as TCM's ( transmission control modules)
NOTES ABOUT THE GEN IV ECM & TCM's
E38 harness connectors from a 2007 Silverado, the connector to the left is for the T42 TCM