Fuel Injection ECM

Engine Management / Fuel Injection:

PURPOSE
The ECM provides precise control of fuel injection to ensure optimum performance and strict emissions compliance.

OPERATION
Various engine sensors and other systems supply ECM with operating information. ECM processes sensor inputs and sends output signals in order to maintain optimum air/fuel ratio. ECM also monitors exhaust gas oxygen content by way of input from a pair of oxygen sensors. When adjustments are needed, ECM varies injector pulse width ("ON" time) as the means of controlling air/fuel ratio.

Input signals include:
^ Engine Speed Signal from Ignition ECM
^ Engine Temperature
^ Throttle Position
^ Lambda Signal
^ Battery Voltage
^ Gear Position (Auto Trans. only)
^ A/C Signal

Output signals include:
^ Fuel Injector Control
^ Idle Speed Control
^ Fuel Pump Control
^ Air Injection Relay
^ Purge Valves
^ Fuel Information - Trip Computer
^ Fuel Fail - Transmission
^ Check Engine Warning
^ Oxygen Sensor Heater Relay

Incorporated into the ECM is a manifold absolute pressure (MAP) sensor used to detect engine load. It is made with a separate diaphragm system to measure and compensate for barometric pressure variations. The sensor is connected by a hose to intake manifold balance pipe.


ON-BOARD DIAGNOSTICS
In the event of a system malfunction, circuit information is stored in the internal memory of the electronic control unit. In addition to being stored in memory, an emissions-related failure will cause the "Check Engine" light to illuminate on the instrument cluster.

ADAPTIVE CONTROL
The electronic control unit has adaptive idle speed, throttle position, and air/fuel mixture capabilities. The control unit continuously compares the programmed data, for idle control and air fuel mixture, with the input values.

If a deviation occurs, the new input values are superimposed and stored in the programmed data map. As a result, new output signals are sent to the idle control valve, and or to the injectors. This allows the electronic control unit to correct the idle speed, or injector pulse width for break-in wear or slight air leaks which might occur in the systems.

If power is interrupted to the control unit, new adaptation takes place within several minutes of engine operation.

Control Unit Locations:

LOCATION