Expo LRV AWD L4-1834cc 1.8L SOHC 16 Valve (1992)
Engine Control Module: Description and Operation
Engine Control Module (ECM)
ECU Location
PURPOSE
The electronic control module (ECM) controls the fuel injection, ignition system and the idle speed system.
CONSTRUCTION
The ECM consists of an 8-bit microprocessor, random access memory (RAM), read only memory (ROM) and an Input/Output (I/0) interface. The ECM
is also able to perform self-diagnostic procedures and provide back-up functions if certain circuits fail.
BASIC OPERATION
The Electronic Control Unit (ECU) controls the fuel injection system, ignition timing, and the idle speed control system. The ECU also interrupts the
operation of the air conditioning and EGR systems, and controls power to the fuel pump (through the control relay). The ECU consists of an 8-bit
microprocessor, random access memory (RAM), read only memory (ROM), and an input/output interface.
Based on information from the input sensors (engine coolant temperature, barometric pressure, air flow, etc.), the ECU determines optimum settings for
the output actuators (injection, idle speed, ignition timing, etc.).
LOCATION
Located above the R.H. kick panel.
SELF-DIAGNOSIS
The electronic control unit constantly monitors input and output signals for correct operating range. If an irregularity occurs, the ECU stores a trouble
code which can be accessed via the self-diagnosis output terminal. Diagnostic results can be read with a voltmeter or multi-use tester.
ECU trouble code memory is maintained by direct battery voltage so diagnostic results are held in memory even if the ignition key is turned off.
However, trouble codes will be erased if the battery terminal or the engine control unit connector is disconnected.
