Ch 6 page 71
ELECTRICAL SYSTEM
SHOP MANUAL
Sensor engine boost temperature
T121, Charge air temperature sensor
Function:
The charge air temperature sensor detects the temperature
in the inlet pipe between the turbocharger and the charge
air cooler.
The engine control unit uses the information from the sen-
sor to control the relationship between the intake air and
EGR gases going to the engine. The sensor also monitors
the temperature of the air coming into the charge air cooler
so that it is not higher than the temperature the charge air
cooler material can withstand.
When there is a high power output the turbocharger rotates
at a high speed. A high turbocharger speed means that the
pressure and thereby the temperature of the air coming into
the charge air cooler increases. If the temperature is higher
than is permitted, the engine control unit limits the power
output by reducing the quantity of fuel injected.
The sensor is of the NTC type, which means that its resis-
tance is temperature dependent. If the temperature increas-
es, the resistance in the sensor drops. The engine control
unit converts the sensor resistance to voltage. If the voltage
is outside a certain range, the engine control unit will work
to a pre-programmed temperature value, and a fault code
will be generated. The engine will then react slower than
normally during throttle application.
Specification
Resistance at 20°C: 2,419 ± 85 Ω.
Temperature sensitivity: Between -40 and +120ºC.
Sensor coolant level monitor
Detach the connector, grasp the sensor firmly and
pull it out from its position under the coolant reservoir.
The sensor is not in direct contact with the coolant so
it is not necessary to drain the coolant.
Figure 56
Figure 54
Figure 55
Figure 53
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