Turbo

The electronic engine control system is a computerized fuel, ignition and emission control system designed to maintain fuel economy, good driveability and reduced vehicle emissions. An Electronic Control Module (ECM) monitors data from various sensors and controls functions such as air/fuel ratio, emission control devices, turbocharger and on-board diagnostics.

The ECM is a computer that judges air/fuel ratio as rich or lean according to oxygen sensor output voltage. Based on oxygen sensor and other input data, the ECM generates a controlling signal to the fuel injectors that regulates "ON" time. Because fuel pressure remains constant, the ECM controls air/fuel ratio adjustments by varying injector "ON" time.

When operating in "Open Loop," the ECM defaults to preprogrammed values for air/fuel ratio control. The system is in "Open Loop" before the oxygen sensor has warmed up to operating temperature. When operating in "Closed Loop," the ECM continually adjusts air/fuel ratio according to oxygen sensor input and operating information received from various other sensors.

This system incorporates self-diagnostic capability that is monitored via a dash mounted "Check Engine" light. When the system detects a fault in a monitored component and/or circuit, the light will come on and stay on (while the engine is running), alerting the driver to seek service. With intermittent problems, the light may come on and then go out, but a trouble code will be stored in ECM memory if correct parameters are met. The technician can then extract trouble codes from the ECM that will aid in the performance of efficient troubleshooting and repair.

To allow one model of ECM to be used for different vehicles, a device called a Memory-Calibration Unit (Mem-Cal) is utilized. The Mem-Cal is located in the ECM and contains information on vehicle weight, engine, transmission, axle ratio, etc. Because the Mem-Cal is vehicle specific, it must be be transferred to a new ECM if the original is being replaced.

To give an extra margin of safety in the event of system failure, the output of the ECM will automatically switch to fail-safe mode if a fault is detected in any of these components and/or systems:

Oxygen sensor
Coolant temperature sensor
Throttle position sensor
MAT sensor
MAP sensor
Vehicle speed sensor
Turbocharger wastegate control system
EGR system
EST system

If a malfunction develops in the micro computer within the control unit, the back-up control system will maintain the minimum necessary ECM functions to permit vehicle operation.

ECM CONNECTIONS

ECM Connector Identification: