Pgm-FI Control System

Injector Timing and Duration
The ECU contains memories for the basic discharge durations 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.

Electronic Idle Control
Idle Control/Fast Idle Control/A/T Idle Control/A/C Idle Boost Solenoid Valves When the engine is cold, the A/C compressor is on, the transmission is in gear (A/T only) or the alternator is charging, the ECU controls these solenoid valves to maintain correct idle speed.

Other Control Functions

1. Starting Control
When the engine is started, the ECU provides a rich mixture.
2. Fuel Pump Control
- When the ignition switch is initially turned on, the ECU supplies ground to the main relay which supplies current to the fuel pump for 2 seconds to pressurize the fuel system.
- When the engine is running the ECU 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 ECU cuts ground to the main relay which cuts current to the fuel pump.
3. Fuel Cut-off Control
- During deceleration with the throttle valve closed, current to the injectors is cut-off at speeds over 1,200 rpm, to improve fuel economy.
- Fuel cut-off action also takes place when engine speed exceeds 6,600 rpm regardless of the position of the throttle valve to protect engine from over running.
4. Ignition Control Solenoid Valve (ICSV)
Whenever the coolant temperature is below 60°C (140°F), when the coolant temperature is 60 - 100°C (140 - 212°F), the ICSV is operated by the ECU which receives signals from the engine speed and manifold vacuum to provide maximum performance and fuel economy, while protecting the engine by preventing detonation from occuring.
5. EGR Control Solenoid Valve (EGRCSV)
When the EGR is required for control of oxides of nitrogen (NOx) emissions, the ECU supplies ground to the (EGRCSV) which supplies regulated vacuum to the EGR valve.

ECU Back-up Functions

1. Fail-Safe Function
When an abnormality occurs in signal from a sensor, the ECU ignores that signals and assumes a pre-programmed value that allows the engine to continue to run.
2. Back-up Function
When an abnormality occurs in the ECU itself, the injections are controlled by a back-up circuit independent of the system in order to permit minimal driving.
3. Self-diagnosis Function (PGM-FI warning light and LED indicator).
When an abnormality occurs in a signal from a sensor, the ECU lights the PGM-FI warning light, stores the failure code in erasable memory and indicates the code with a LED on the ECU anytime the ignition is on. When the ignition is initially turned on, the ECU supplies ground for the PGM-FI warning light for about 2 seconds.