Mercedes-Benz OM 471 Introduction Into Service Manual page 142

GF49.20>W>3013HA
ENGINES 471.9 in MODEL 963, 964 with CODE (M5Z) Engine version Euro VI
ENGINES 471.9 in MODEL 963, 964 with CODE (M5R) Engine version EEV
Location
1 Exhaust aftertreatment unit
B72 Exhaust temperature sensor
upstream of SCR catalytic converter
Task
The exhaust aftertreatment (ACM) control
unit (A60) registers the temperature of the
exhaust flow in the inlet tube of the
exhaust aftertreatment unit (1) via the
temperature sensor exhaust upstream of
the SCR catalytic converter (B72).
Design
The exhaust temperature sensor upstream of SCR catalytic
converter (B72) consists of a stainless steel housing. The inside
contains a measuring element, a PTC resistor. PTC stands for
"Positive Temperature Coefficient" and means that the electrical
resistance increases as the temperature increases.
i Introduction of engine OM 471 and exhaust aftertreatment > 09/2011 >
Exhaust temperature sensor upstream of SCR catalytic converter, component
description
– This printout will not be recorded by the update service. Status: 09 / 2011 –
System components
Function
The exhaust blowing by the sensor influences the measuring
element on the inside depending on its temperature and leads to
a change in its electric resistance.
Since a constant measurement current flows through the exhaust
temperature sensor upstream of SCR catalytic converter (B72),
there is a voltage drop due to the change in resistance, which the
exhaust aftertreatment (ACM) control unit (A60) can use to derive
the associated temperature value.
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