Civic Sedan L4-1493cc 1.5L SOHC (D15B2) TBI (1989)
Engine Control Module: Description and Operation
General System Description
Fig. 2 Electronic Control Unit And Atmospheric Pressure (PA) Sensor
The PGM-FI (ECU), located under the carpet on the passenger floorboard, is the primary controller for the fuel system. The ECU itself consists of
a dedicated microprocessor, a small amount of volatile memory, and the control program contained in read only memory (ROM). The ECU
monitors the absolute manifold pressure and the engine speed to determine the basic "ON" time (amount of time the injectors are open and
injecting fuel) for the fuel injectors. Before the ECU actually alters the injector "ON" time, the other data inputs (intake air temperature sensor,
oxygen sensor, etc.) are used to determine the final air/fuel mixture. After the final "ON" time has been determined, the ECU then applies this to
the injectors. For a more detailed explanation of the ECU function see "COMPUTERIZED ENGINE CONTROLS".