Contents: PGM-FI system ⇊ Fuel injection advance and duration ⇊ Regulation of air supply at idle…⇊ Ignition timing control ⇊ Other management functions ⇊ ECM/PCM module fail-safe/redundancy…⇊
PGM-FI system
The PGM-FI system on this model is a sequential multi-point fuel injection system.
Fuel injection advance and duration
The ECM/PCM module memory contains basic values of injection duration at different engine speeds and manifold pressures. After reading this duration from the memory, corrections are made 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 gear *4, the brake pedal is depressed *5, the power steering load is high, or the alternator is charging, the ECM/PCM regulates the current flow to the IAC valve to maintain the proper idle speed.
Ignition timing control
The ECM/PCM stores base ignition timing values at various engine speeds and manifold airflows. The ignition timing values are also adjusted for engine coolant temperature.
Other management functions
1. Engine start control
- When the engine is started, the ECM/PCM ensures a rich mixture by increasing the fuel injection duration.
2. Fuel pump control
- When the ignition switch is initially turned to the ON (II) position, 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 supplies current to the fuel pump.
- When the engine is not running and the ignition switch is in the ON (II) position, the ECM/PCM interrupts the ground to the PGM-FI main relay, which cuts current from the fuel pump.
3. Fuel cut-off control
- When decelerating with the throttle closed, the current from the fuel injectors is cut off and fuel consumption at speeds above 1100 rpm is reduced.
- Fuel cut also occurs when engine speed exceeds 6900 rpm (rpm) regardless of throttle position to prevent engine overspeed.
4. Air conditioning compressor clutch relay
- When the A/C system signals the ECM/PCM to cool, it delays the compressor power and enriches the mixture to ensure a smooth transition to A/C mode.
5. Generator control *5
- The system regulates the voltage generated by the generator according to the electrical load and driving mode, reducing the load on the engine and fuel consumption.
6. EVAP filter purge solenoid valve*1
- When the engine coolant temperature is below 74°C, the ECM/PCM provides ground to the EVAP canister purge solenoid valve, which cuts the vacuum to the EVAP canister.
ECM/PCM module fail-safe/redundancy functions
1. Fault tolerance function
- When an abnormal signal is received from any sensor, the ECM/PCM ignores the signal and uses the pre-programmed value for that sensor, allowing the engine to continue running.
2. Reservation function
- When an abnormal situation occurs in the ECM/PCM module itself, the fuel injector control switches to a backup circuit independent of the system in order to allow the driver to reach the nearest service station.
3. Self-diagnosis function (MIL) When an abnormal signal is input from any sensor, the ECM/PCM provides ground to the MIL and stores the code in the rewritable memory. When the ignition switch is initially turned to the ON (II) position, the ECM/PCM provides ground to the MIL for two seconds and checks the MIL status.
[The original is located on the website: HONDABOOK]