PGM-FI system
The PGM-FI system on this model is a sequential multipoint fuel injection system.
Advance and duration of fuel injection
The ECM/PCM stores base values for injection duration at various engine speeds and manifold pressures. This duration, after it is read from the memory, is corrected based on signals from various sensors and the final injection duration is formed.
Regulation of air supply at idle speed
When the engine is cold, the A/C compressor is on, the transmission is in '4' gear, the brake pedal is depressed*5, the hydraulic booster load is high or the alternator is charging, the ECM/PCM modulates the current to the IAC valve to maintain the proper idle speed.
Ignition advance control
The ECM/PCM stores basic ignition timing values at various engine speeds and manifold airflows. Ignition advance values are also corrected for engine coolant temperature.
Other control functions
1. Engine start control
- When the engine is started, the ECM/PCM provides a rich mixture by extending the duration of the fuel injection.
2. Fuel pump control
- When the ignition key is initially turned to the ON position (II) The ECM/PCM provides ground to the PGM-FI main relay, which energizes the fuel pump for two seconds to pressurize the fuel system.
- When the engine is running, the ECM/PCM provides ground to the PGM-A main relay, which energizes the fuel pump.
- When the engine is not running and the ignition key is in the ON position (II), the ECM/PCM interrupts ground to the PGM-FI main relay, which cuts off current from the fuel pump.
3. Fuel cut control
- When decelerating with a closed throttle valve, the current from the fuel injectors is cut off and fuel consumption is reduced at speeds above 1100 rpm.
- Fuel cut also occurs when engine speed is over 6900 rpm (min') regardless of throttle position to prevent engine runaway.
4. A/C compressor clutch relay
- When the A/C signal is given to the ECM/PCM to cool, it delays the compressor power-up and richens the mixture to ensure a smooth transition to air conditioning mode.
5. Generator control *5
- The system adjusts the voltage generated by the alternator in accordance with the electrical load and driving mode, reducing engine load and fuel consumption.
6. Evaporative filter purge solenoid valve (EVAP) *1
- When the engine coolant temperature is below 74"C, ECM/PCM provides ground to evaporative filter purge solenoid valve (EVAP), which cuts off the vacuum to the EVAP carbon filter.
ECM/PCM Failover/Redundancy Functions
1. Fail safe function
- When an abnormal signal is supplied from any sensor, the ECM/PCM will ignore the signal and use the pre-programmed value for that sensor, allowing the engine to continue running.
2. Backup function
- When an abnormal situation occurs within the ECM/PCM itself, the fuel injector control switches to a backup circuit independent of the system in order to allow the driver to drive to the nearest service station.
3. Self-diagnosis function (MIL malfunction indicator lamp) When an abnormal signal is supplied from any sensor, the ECM/PCM provides ground to the MIL and writes a code to writable memory. When the ignition key is initially turned to the ON position (II) The ECM/PCM provides a ground to the MIL for two seconds and checks the status of the MIL.