Summit Wagon AWD L4-1795cc 1.8L SOHC (1994)
Engine Control Module: Description and Operation
Engine Control Module (ECM)
ECU Location
PURPOSE
The Engine Control Module (ECM) controls fuel injection, ignition timing, and idle speed. In addition it interrupts the operation of the air
conditioning and EGR systems and controls power to the fuel pump--through the control relay.
OPERATION
The ECM 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 ECM determines optimum
control of fuel injection, idle speed, ignition timing, etc..
Three communication lines are connected between the engine control module and the transaxle control module to send and receive the engine and
transaxle total control signal.
SELF-DIAGNOSIS
The ECM constantly monitors input and output signals for correct operating range. If an irregularity occurs the ECM 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.
ECM 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.
