With F23A4 Engine

PGM-FI System
The Programmed Fuel Injection (PGM-FI) system is a sequential multi port fuel injection system.

Fuel Injector Timing and Duration
The ECM/PCM contains the memory for basic discharge duration at various engine speeds and manifold pressures. The basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors to obtain the final discharge duration.
By monitoring Long Term Fuel Trim, the ECM/PCM detects long term malfunctions in the fuel system, and will set a Diagnostic Trouble Code (DTC) if the malfunction occurs during two consecutive trips.

Ignition Timing Control
The ECM/PCM contains the memory for basic ignition timing at various engine speeds and manifold air flow rates. It also adjusts the timing according to engine coolant temperature. The ECM/PCM detects misfiring by using the CKP sensor to monitor fluctuations in crankshaft speed. It will then set DTCs depending on how much misfiring occurs.

Starting Control
When the engine is started, the ECM/PCM provides a rich mixture by increasing fuel injector duration.

Alternator Control
The alternator signals the ECM/PCM during charging. The ECM/PCM then controls the voltage generated at the alternator according to the electrical load determined by the ELD (Electrical Load Detector) and driving mode. This reduces engine load to improve fuel economy.

A/C Switch
The A/C (air conditioning) switch signals the ECM/PCM whenever there is a demand for cooling.

A/C Compressor Clutch Relay
When the ECM/PCM receives a demand for cooling from the A/C system, it delays the compressor from being energized, and enriches the mixture to assure smooth transition to the A/C mode.

CKP (Crankshaft position) and TDC (Top Dead Center) Sensors




The CKP sensor determines fuel injection timing and ignition timing for each cylinder, and also detects engine speed. The TDC sensor determines ignition timing at start-up and when crankshaft position signal is abnormal.




CYP (Cylinder Position) Sensor
The CYP sensor inside the distributor detects the position of the No.1 cylinder as a reference for sequential fuel injection to each cylinder.




MAP (Manifold Absolute Pressure) Sensor
The MAP sensor converts manifold absolute pressure into electrical signals to the ECM/PCM.




IAT (Intake Air Temperature) Sensor
The IAT sensor is a temperature dependent resistor (thermistor). The resistance of the thermistor decreases as the intake air temperature increases.




ECT (Engine Coolant Temperature) Sensor
The ECT sensor is a temperature dependent resistor (thermistor). The resistor of the thermistor decreases as the Engine Coolant temperature increases.




TP (Throttle Position) Sensor
The TP sensor is a potentiometer connected to the throttle valve shaft. As the throttle position changes, the sensor varies the signal voltage to the ECM/PCM. The TP sensor is not replaceable apart from the throttle body.

VSS (Vehicle Speed Sensor) (M/T)
The speed sensor is driven by the differential. It generates a pulsed signal from an input of 5 volts. The number of pulses per minute increases/decreases with the speed of the vehicle.

Baro (Barometric Pressure) Sensor
The barometric pressure sensor is inside the ECM/PCM. It converts atmospheric pressure into a voltage signal that modifies the basic duration of the fuel injection discharge.




Primary and Secondary HO2S (Heated Oxygen sensors)
The heated oxygen sensors detect the oxygen content in the exhaust gas and sends signals to the ECM/PCM which varies the duration of fuel injection accordingly. To stabilize its output, the sensor has an internal heater. The primary sensor is installed in the exhaust manifold.
The secondary HO2S, installed in the TWC, detects the oxygen content in the exhaust gas downstream of the TWC and sends signals to the ECM/PCM, which varies the duration of fuel injection accordingly. To stabilize it's output, the sensor has an internal heater.
By controlling the air/fuel ratio with primary and secondary HO2 sensors, the deterioration of the primary sensor can be evaluated by its feedback period. When the feedback period exceeds a certain value during stable driving conditions, the sensor is considered deteriorated and the ECM/PCM sets a DTC.




Knock Sensor
The knock control system adjusts the ignition timing for the octane rating of the gasoline used.