Fiat 1996 Brava Service Manual page 450

Engine
Fuel system
16v
Bravo- Brava W
1998 range
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4A38IJ01
Pin 1 - Air pressure sig­
nal
Pin 2 - Positive
Pin 3 - Air temperature
signal
Pin 4 - Negative
Connector wiring
The numbers indicate the corresponding control
unit pins
pc
— 1 - H
— 2 - H
— 3 - H
1 -
<S>
13
Checking the resistance
The table alongside shows resistance values that
the temperature sensor (NTC thermistor) may as­
sume with changing temperature. These values
may be measured by connecting an ohmmeter
across sensor pins 3 and 4.
INTAKE AIR PRESSURE AND
PERATURE SENSOR (T-PRT 03)
T E M -
The intake air pressure and temperature sensor
is a built-in component that measures the
temperature and pressure of air inside the in­
take manifold.. The injection control unit uses
both items of information to define the
amount of air taken in by the engine. This in­
formation is then used to compute injection
time and ignition point. The sensor is fitted to
the inlet manifold.
Self-diagnosis and recovery
The self-diagnostic system monitors both sen­
sor output signals.
It identifies the following for both signals:
- Short circuit to earth.
- Short circuit to positive and reference volt­
age.
- Circuit open/broken.
When the sensor pressure signal is cut off, the
throttle potentiometer signal and engine rpm
signals are used to computer injection time
and ignition point. The injection control unit
processes these signals to reconstruct the
missing signal. If the air temperature sensor
fails, the injection control unit uses the last
reading as a recovery value or, if the fault is
present when the engine is started, it uses a
fixed value of 45°C and mixture self-
adaptation is disabled.
If the pressure sensor faults, a fixed value of
1024 mBars is used.
Temperature (°C)
-40
-20
0
10
20
25
30
40
50
60
80
100
Resistance (Q)
49933 ± 13.6%
15701 ± 10.8%
5959 ± 8.5%
3820 ± 7.4%
2509 ± 6.5%
2051 ±6.0%
1686 ± 6.0
1157 ± 5.9%
810 ± 5.8%
578 ± 5.7%
309 ± 5.5%
176 ± 5.4%
38
Publication n ° 506.670/21