Hyundai Sonata 1991 Shop Manual page 279

MPI SYSTEM
Atmospheric Pressure Sensor [For Australia]
Y31ECOA
The atmospheric pressure sensor installed on the AFS senses
the atmospheric pressure and converts it into a voltage which
is sent to the ECU.
The ECU uses this signal to compute the altitude at which the
vehicle is running and corrects accordingly the air-fuel ratio to
the optimum and also corrects the ignition timing, thus improv-
ing driveability at high altitude.
Atmospheric pressure sensor
31Y081
1. Connect a voltmeter between terminals 5 and 6 of the atmos-
pheric pressure sensor connector.
Terminal 5 : Atmospheric sensor connector.
Terminal 6 : Sensor ground
2. Warm the engine and bring it to a normal idle.
3. Slowly cover about half of the air cleaner air intake, checking
the change in voltage.
Reference
Pressure
Fall
Voltage
Drop
Pressure mmHg (kPa, psi)
150
350 760
(20, 2.9)
(49, 6.9) (103, 15)
Central voltage (V)
0.79 1.84
4.00
4. Replace the air flow sensor if necessary.
The intake air temperature sensor, located at the illustrated posi-
tion on AFS, is a resistor-based sensor for detecting the intake
air temperature.
According to the intake air temperature information from the sen-
sor, the ECU provides necessary fuel injection amount control.
Intake Air Temperature Sensor
Y31EDOA
31Y083
31-54