Location
1 | Exhaust aftertreatment unit |
B67 | Exhaust temperature sensor upstream of diesel oxidation catalytic converter |
W49.20-A001-76
Task
Via the exhaust gas temperature sensor upstream of the diesel oxidation catalytic converter, the aftertreatment control module (ACM 3.0) (A60a) detects the temperature of the exhaust flow in the inlet chamber of the exhaust gas aftertreatment unit (1).
Structure
The sensor consists of a stainless steel housing. The housing contains a measuring element, a PTC resistor. PTC stands for "Positive Temperature Coefficient" and means that the electrical resistance increases as the temperature increases.
Function
The exhaust gas blowing by past the sensor influences the measuring element in its interior depending on temperature. More specifically, this changes its electrical resistance. So that this change in resistance becomes a measurable initial parameter, a constant measuring current flows through the sensor. Due to the associated voltage drop, the aftertreatment control module can initially derive the resistance value and thus the associated temperature value.