t
14-18
FUEL SYSTEM - Sensors
BAROMETRIC PRESSURE SENSOR
Engine control unit
1
Barometnc pressure sensor
Barometnc rxessure sensor
OFUO576
/
EC1537
760 (30) Barometric pressure mmHg (in.Hg)
A barometric pressure sensor is alas mounted on the aif flow sensor. It senses the barometric pressure and converts it to electrical voltage which is sent as a signal to the engine control unit. Using this signal, the engine control unit calculates the altitude of.the location where the vehicle is, and corrects the fuel injection quantity for the optimum air-fuel ratio at that altitude, and also corrects the
COOLANT
EC1551
ignition timing. This ensures improved driveability at high altitudes. The barometric pressure sensor converts the pressure to a voltage making use of the fact that the resistance of a strain gauge changes in direct proportion to the pressure as shown in this diagram relationship between which illustrates the barometric pressure and output voltage.
TEMPERATURE SENSOR
Engine control unit
Coolant temperature sensor -a
5 volts drt LizI
* Terminal 2
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es h6EL0069
SFUOLSL
L
0 (321
The engine coolant temperature sensor installed in the coolant passage of the thermostat case is a thermistor whose resistance changes with the engine coolant temperature. T h e annine control unit iudoes t h e e n o i n e w a r m UD
20 (68)
Coolant temperature -
state based on the output voltage of this sensor and provides optimum mixture enrichment when the engine is cold. The sensor characteristics are as shown above. .:I