For 1988 and 1989 vehicles, the logic and power modules were combined into one module and located in the same spot as the power module was on previous models. This module is known as the SMEC (single module engine controller), but the logic and power module circuit boards actually remain separate and distinct inside the SMEC case (they are even potted separately). This greatly reduced the amount of wiring needed between the passenger compartment and the engine bay, but the signals between the two boards inside still pass through the wiring locally. The 60-way connector leads to the logic board while the 14-way connector leads to the power board.

Functionally, the 1988 and 1989 TBI SMECs are the same and are therefore interchangeable. Internally however they do differ, particularly in the software. The 1988 SMECs are based largely on the 1987 logic module code, while the 1989 SMECs appear to have a great deal of new code. This provided some additional functionality, such as greater on board diagnostic capability, returning from limp-in mode while driving if a sensor starts working again, etc).