Circuit description
The
air
filter temperature sensor consists of a thermis-
tor which forms a closed circuit with an internal resistor
in the engine control unit (EMS2). The thermistor resis-
tor changes in a non-linear manner, depending on the
air temperature. The EMS2 provides the circuit with a
reference voltage of +5 Volt. The EMS2 measures the
voltage drop over the thermistor via pin 18 and pin 31
on the EMS2. Pin 3 on the sensor is connected to bat-
tery negative via pin 18 on the EMS2. When the air into
the filter is cold, the thermistor resistance is high and
the EMS2 senses a high voltage drop. As the air into
the filter warms up, the resistance in the thermistor falls
and the voltage drop across it falls.
Please refer to the table, “resistance/temperature” in
this fault code chapter.
Measurements
Checking signal cable, air filter temperature
switch page 160
Checking negative cable, air filter temperature
switch page 161
Checking the sensor cable for open circuit or
shortcircuit page 162
Checking air inlet temperature sensor page 163
P0013492
EMS2
15
29
18
31
SB
SB
BL / GN
OR
P
2
1
3 4
A
B
C
P0013493
a Connector A
b Connector B
c Air filter pressure and temperature
30-2 Fault Tracing
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