Operation Section
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(6) Fuel Temperature Sensor
• This is a thermistor type sensor that detects the fuel temperature. In the HP2, HP3, and HP4 systems, this sensor is
installed on the supply pump unit, but in the HP0 system, it is installed on a leak pipe from an injector.
(7) Intake Air Temperature Sensor and Atmospheric Pressure Sensor
• This sensor is a semiconductor type sensor. It measures pressure utilizing the piezoelectric effect that when the pres-
sure on the silicon element in the sensor changes, its electrical resistance changes. In addition, the air pressure on
this sensor is switched between the pressure within the intake manifold and the atmospheric pressure, so both the
intake air pressure and the atmospheric pressure are detected with one sensor. The switching between intake air
pressure and atmospheric pressure is handled by the VSV (vacuum switching valve). When any one of the conditions
below is established, the VSV is switched ON for 150 msec. by command of the engine ECU to detect the atmospheric
pressure. When none of the conditions below is established, the VSV is switched OFF to detect the intake air pres-
sure.
Atmospheric Pressure Measurement Conditions
- Engine speed = 0 rpm
-Starter ON
- Stable idling state
Resistance - Temperature
Characteristic
Temperature
Resistance Value
Thermistor
Q000848E
Q000885E
VC
PIM
E2
Absolute Pressure
PIM Output Voltage -
Pressure
Characteristic
Output Voltage
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