Intake Air Pressure And Temperature Sensor (T-Prt 03); Automatic Diagnosis And Recovery - Fiat 1998 Marea Service Manual

Engine
Fuel system
10.
P4F38IJ02
Wiring connector
The numbers in boxes indicate the corre-
sponding control unit pins.
Checking resistance
The table alongside shows resistance values
that the temperature sensor (NTC thermistor)
may assume at different temperatures. These
values may be measured by connecting an
ohmmeter to the terminals of sensor pins 3
and 4.
38
Pin 1 -Air pressure sig-
nal
Pin 2-Positive
Pin 3-Air temperature
signal
Pin 4-Negative
Marea-Marea Weekend^
INTAKE AIR PRESSURE AND TEMPERA-
TURE SENSOR (T-PRT 03)
The intake air pressure and temperature sen-
sor is an integral component. It measures air
pressure and temperature inside the intake
manifold. The injection control unit needs
both items of information to establish the
amount of air taken up by the engine. This in-
formation is then used to compute injection
time and ignition point. The sensor is fitted to
the intake manifold.

Automatic diagnosis and recovery

The self-diagnostic function monitors the
two sensor output signals.
This detects the following for both signals:
- Short-circuit to earth.
- Short circuit to positive and reference volt-
age.
- Circuit open / interrupted
When the sensor pressure signal required to
calculate injection time and ignition point is
not present, the throttle potentiometer signal
and engine rpm signal are used instead.
These are processed by the electronic control
unit to reconstruct the missing signal. If the
air temperature sensor breaks, the injection
control unit uses the last reading as the re-
covery temperature. If the fault occurs upon
start-up, it assumes a fixed value of 45 °C
and mixture self-adaption is disabled.
If the pressure sensor fails, a fixed value of
1024 mBar is used.
Temperature (°C)
-40
- 2 0
0
10
20
25
30
40
50
60
80
100
1*
1998 range
Resistance (£1)
4 9 9 3 3 ± 13.6%
15701 ± 10.8%
5 9 5 9 ± 8.5%
3 8 2 0 ± 7.4%
2 5 0 9 ± 6.5%
2051 ± 6.0%
1686 ± 6.0%
1157 ± 5.9%
8 1 0 ± 5.8%
578 ± 5.7%
3 0 9 ± 5.5%
176 ± 5.4%
Publication no. 506.763/09