3-30 FUEL SYSTEM (DFI)
The ECU takes the following measures to prevent engine damage when the DFI or the ignition
system parts have troubles.
(1) D-J Method: The DFI control method from medium to heavy engine load. When the engine
load is light like at idling or low speed, the ECU determines the injection quantity by calculating from
the throttle vacuum (intake air pressure sensor output voltage) and engine speed (crankshaft sensor
output voltage). This method is called D-J method.
(2) α-N Method: As the engine speed increases, and the engine load turns middle to heavy, the
ECU determines the injection quantity by calculating from the throttle opening (main throttle sensor
output voltage) and the engine speed. This method is called α-N method.
Output Signal Usable
Range or Criteria
Throttle Sensor Output
0.391 ∼ 4.512 V
Intake Air Pressure
0.352 ∼ 4.824 V
Intake Air Temperature
0.117 ∼ 4.922 V
0.195 ∼ 4.902 V
Crankshaft sensor must
send 18 signals (output
signal) to the ECU at
the one cranking.
Gear Position Sensor
0.469 ∼ 4.727 V
0.195 ∼ 4.609 V
In succession pulse is
input to ECU.
6 ∼ 15 V
Send signals (output
voltage) continuously to
Backups by ECU
If the throttle sensor system fails (the signal is
out of the usable range, wiring short or open),
the ECU locks ignition timing into the closed
throttle position and sets the DFI in the D-J
Also, the throttle sensor system and intake air
pressure fails, the ECU locks ignition timing
into the closed throttle position and sets the
DFI in the α-N method (2).
If the intake air pressure sensor system fails
(the signal is out of the usable range, wiring
short or open), the ECU sets the DFI in the α
- N method.
Conduct ignition and injection operations
whenever crank rotates by 360 degrees.
ECU sets the intake air temperature at 26°C.
ECU sets the water temperature at 80°C.
If the crankshaft sensor generates other than
18 signals, the engine stops by itself.
If the gear position switch fails, the ECU sets
the low (1st) gear position.
If the vehicle-down sensor system fails, the
ECU shuts off the fuel system and the ignition
system. ECU does not backup.
If the injector break down, wiring short or open,
the ECU stops the signal input to injector and
the fuel delivery to cylinder is stopped.
If the pump fails, wiring short or open, the ECU
stops the pump operations.
If the ignition coil fails, the ECU shuts off the
signal to the ignition coil.