Sensor, Exhaust Temperature: Operation

The Exhaust Temperature sensors are used by the Powertrain Control Module (PCM) to monitor the engine exhaust temperatures in the aftertreatment system. The Exhaust Temperature sensors are thermistors and change resistance based on the temperature being measured. The PCM provides a 5-Volt reference voltage to the sensor. The PCM monitors the voltage on the signal pin and converts this to a temperature value. This fault is set by the PCM if it detects that the Diesel Oxidation Catalyst (DOC) inlet temperature is not increasing along with the engine operating temperature after engine start up. The PCM will illuminate the MIL lamp after the diagnostic runs and fails on two consecutive drive cycles. The PCM will turn off the MIL lamp after the diagnostic runs and passes on four consecutive drive cycles.
When the exhaust gas temperature is cold, the sensor resistance is high, the Powertrain Control Module (PCM) will sense the resistance and sense the exhaust temperature as cold. When the exhaust gas temperature is high, the sensor resistance is low, the PCM will sense the resistance and sense the exhaust temperature as high.