The following file (PDF) contains wiring diagram and electrical schematic for 1990 Pontiac Grand Prix V6 3.1L engine control module (ECM), pin-out and connectors. The 1990 Pontiac Grand 3.1L engine control module 1990 Pontiac Grand 3.1L is designated to manage the engine control system such as adjusts the air/fuel mixture and utilizes a catalytic converter to minimize the amount of pollution produced from the engine. Find more information about 1990 Pontiac Grand 3.1L Wiring Diagram for ECM Pin-out and Connectors here – free download PDF file.