Other Control Functions

PGM-FI ECM FUNCTIONS
Starting Control
^ When the engine is started, the PGM-FI ECM increases fuel injector duration to provide a rich mixture.

Fuel Pump Control
^ When the ignition switch is initially turned on, the PGM-FI ECM supplies ground to the main relay which supplies current to the fuel pump for two seconds to pressurize the fuel system.
^ When the engine running, the PGM-FI ECM supplies ground to the main relay which supplies current to the fuel pump.
^ When the engine is not running and the ignition is on, the PGM-FI ECM cuts ground to the main relay which cuts current to the fuel pump.

Fuel Cut-off Control
^ During deceleration with the throttle valve closed, current to the injectors is cut off at speeds over 1100 rpm to improve fuel economy.
^ Fuel cut-off action also takes place when engine speed exceeds 7700 rpm, regardless of the position of the throttle valve to protect the engine from over-running.

A/C Compressor Clutch Relay
^ When the PGM-FI ECM receives a demand for cooling from the air conditioning system (compressor control unit), it delays the compressor from being engaged, and enriches the fuel mixture to assure smooth transition to the A/C mode.

Purge Cut-off Solenoid Valve
^ When the coolant temperature is below 158°F (70°C), the PGM-FI ECM supplies a ground to the purge cut-off solenoid valve which cuts vacuum to the purge control valve.

Intake Air Bypass Control Solenoid Valve (IAB)
^ When the engine speed is below 4600 rpm, the IAB Control Solenoid Valve is activated by the PGM-FI ECM, intake air flows through the long intake path and high torque is delivered. At engine speeds above 4600 rpm the solenoid valve is de-activated by the PGM-FI ECM and intake air flows through the short intake path reducing resistance in airflow.

Intake Control Solenoid Valve
^ When the engine speed is below 4000 rpm, the PGM-FI ECM supplies ground to the Intake Control Solenoid Valve. This opens the solenoid valve sending intake manifold vacuum to the intake control diaphragm. This allows intake air to flow through the long air intake system including the air box resonator for increased torque.

EGR Control Solenoid Valve (EGR CSV)
^ When the EGR is required for control of oxides of nitrogen (NOx) emissions, the PGM-FI ECM supplies ground to the EGR CSV which supplies regulated vacuum to the EGR valve.

Alternator Control
^ The system controls the voltage generated at the alternator according to the electric load and drive mode, and reduces the engine load to improve the fuel economy.

Transmission control Signals A and B.
^ These signals are used as a means of communications between the PGM-FI ECM and the A/T ECM so that engine parameters can be adjusted prior to shifting. This preserves peak fuel efficiency, power generation, and comfort.

A/T Shift Position Signal
^ The A/T Shift Position switch is fitted to base of gear selector lever, its internal connections are switched to either open or closed depending on the selector lever position. The shift position switch has four functions.
^ To ensure that the starter motor will only operate in positions P or N (interlock control).
^ To switch the back-up lights on when R is selected.
^ To inform the PGM-FI ECM when a drive position is selected so idle speed can be increased.
^ Informs the shift position display panel which indicator lamp to illuminated.