3-34 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 and α - N Method: When the engine load is light like at idling or low speed, the ECU
determines the injection quantity by calculating from the throttle vacuum (inlet air pressure sensor
output voltage) and engine speed (crankshaft sensor output voltage). This method is called D-J
method (low-speed mode). 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 (throttle
sensor output voltage) and the engine speed. This method is called α - N method (high-speed
Output Signal Usable
Range or Criteria
Throttle Sensor Output
0.391 ∼ 4.512 V
Inlet Air Pressure
0.352 ∼ 4.824 V
Inlet 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
0.176 ∼ 4.727 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 ignition
timing at closed throttle position and sets the
DFI in the D-J method.
Also, the throttle sensor system and inlet
air pressure fails, the ECU locks ignition
timing into the ignition timing at closed throttle
position and sets the DFI in the α-N method.
If the inlet air pressure sensor system fails (the
signal Pv 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 Ta at 26°C.
ECU sets Tw at 80°C.
If crankshaft sensor generates other than 18
signals, the engine stops by itself.
If the gear position switch fails, set the low (1)
If the vehicle-down sensor system has failures,
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.